changed settings saving (#3)

Reviewed-on: #3
Co-authored-by: Aleksandr Neychev <alexnejchev73@gmail.com>

CursorLang.Agent/Windows/NativePopupWindow.cs

@@ -91,8 +91,17 @@ internal sealed class NativePopupWindow : NativeWindow, ILayoutPopupWindow
 
         PopupWindowNative.Point position = atFixedPoint
             ? PopupLayout.OnScreen(
-                work, _settings.ScreenPosition, PopupLayout.ToPixels(_settings.ScreenMargin, scale), width, height)
-            : PopupLayout.NearAnchor(anchor, AnchorSideForMode(), OffsetForMode(scale), width, height);
+                work,
+                _settings.FixedPoint.Position,
+                PopupLayout.ToPixels(_settings.FixedPoint.Offset, scale),
+                width,
+                height)
+            : PopupLayout.NearAnchor(
+                anchor,
+                SideForMode(),
+                PopupLayout.ToPixels(_settings.Current.Offset, scale),
+                width,
+                height);
 
         if (!Draw(text, position, width, height, PopupLayout.ToPixels(CornerRadius, scale)))
         {
@@ -169,7 +178,7 @@ internal sealed class NativePopupWindow : NativeWindow, ILayoutPopupWindow
             RoundTheCorners(bits, width, height, radius);
 
             var size = new WindowNative.Size { Width = width, Height = height };
-            var alpha = (byte)Math.Clamp(Math.Round(_settings.Opacity * 255), 0, 255);
+            var alpha = (byte)Math.Clamp(Math.Round(_settings.Current.Opacity * 255), 0, 255);
 
             return WindowNative.SetContent(Handle, at, size, memory, alpha);
         }
@@ -193,7 +202,7 @@ internal sealed class NativePopupWindow : NativeWindow, ILayoutPopupWindow
 
     private void Fill(IntPtr bits, int width, int height)
     {
-        Color background = _settings.BackgroundColor;
+        Color background = _settings.Current.BackgroundColor;
 
         // Straight into the bitmap rather than through a brush: the pixels have to be
         // written anyway to carry an alpha channel GDI would not touch
@@ -218,7 +227,7 @@ internal sealed class NativePopupWindow : NativeWindow, ILayoutPopupWindow
 
         IntPtr previousFont = GdiNative.SelectObject(deviceContext, _font);
         GdiNative.SetBkMode(deviceContext, GdiNative.TRANSPARENT);
-        GdiNative.SetTextColor(deviceContext, GdiNative.ToColorRef(_settings.ForegroundColor));
+        GdiNative.SetTextColor(deviceContext, GdiNative.ToColorRef(_settings.Current.ForegroundColor));
 
         GdiNative.DrawText(deviceContext, text, text.Length, ref bounds,
             GdiNative.DT_SINGLELINE | GdiNative.DT_CENTER | GdiNative.DT_VCENTER |
@@ -333,13 +342,11 @@ internal sealed class NativePopupWindow : NativeWindow, ILayoutPopupWindow
         return PopupLayout.AsAnchor(PopupWindowNative.GetCursorPosition());
     }
 
-    // Every anchor mode has a side and an offset of its own
-    private AnchorSide AnchorSideForMode() =>
-        _settings.PlacementMode == PopupPlacementMode.AtCaret ? _settings.CaretSide : _settings.CursorSide;
-
-    private int OffsetForMode(double scale) => PopupLayout.ToPixels(
-        _settings.PlacementMode == PopupPlacementMode.AtCaret ? _settings.CaretOffset : _settings.CursorOffset,
-        scale);
+    // The caret has two sides to choose from and the cursor has six, so each mode names
+    // its own side in its own terms
+    private AnchorSide SideForMode() => _settings.PlacementMode == PopupPlacementMode.AtCaret
+        ? _settings.AtCaret.Anchor
+        : _settings.AtCursor.Side;
 
     private Size MeasureText(string text)
     {
@@ -364,11 +371,12 @@ internal sealed class NativePopupWindow : NativeWindow, ILayoutPopupWindow
     }
 
     // The font is rebuilt only when the size in the settings or the monitor scale
-    // changes: it is the one expensive thing a show does
+    // changes: it is the one expensive thing a show does. A switch of the placement
+    // mode counts as a change of the size, since the size belongs to the mode
     private void EnsureFont(double scale)
     {
         if (_font != IntPtr.Zero &&
-            Math.Abs(_fontSize - _settings.FontSize) < 0.01 &&
+            Math.Abs(_fontSize - _settings.Current.FontSize) < 0.01 &&
             Math.Abs(_fontScale - scale) < 0.01)
         {
             return;
@@ -376,7 +384,7 @@ internal sealed class NativePopupWindow : NativeWindow, ILayoutPopupWindow
 
         ReleaseFont();
 
-        _fontSize = _settings.FontSize;
+        _fontSize = _settings.Current.FontSize;
         _fontScale = scale;
         _font = GdiNative.CreateFont(_fontSize, scale);
     }

CursorLang.Core.Tests/Models/AppSettingsTests.cs

@@ -16,18 +16,115 @@ public sealed class AppSettingsTests
         Assert.Equal("en", settings.Language);
         Assert.Equal(AppTheme.System, settings.Theme);
         Assert.Equal(PopupPlacementMode.AtCursor, settings.PlacementMode);
-        Assert.Equal(AnchorSide.BottomRight, settings.CursorSide);
-        Assert.Equal(16, settings.CursorOffset);
-        Assert.Equal(AnchorSide.BottomRight, settings.CaretSide);
-        Assert.Equal(16, settings.CaretOffset);
-        Assert.Equal(ScreenPosition.BottomRight, settings.ScreenPosition);
-        Assert.Equal(24, settings.ScreenMargin);
-        Assert.Equal(20, settings.FontSize);
-        Assert.Equal(0.9, settings.Opacity);
         Assert.Equal(500, settings.DurationMilliseconds);
         Assert.Equal(300, settings.CapsLockHoldMilliseconds);
-        Assert.Equal(Color.FromArgb(0x20, 0x20, 0x20), settings.BackgroundColor);
-        Assert.Equal(Color.FromArgb(0xFF, 0xFF, 0xFF), settings.ForegroundColor);
+    }
+
+    [Fact]
+    public void Every_mode_starts_out_looking_the_same()
+    {
+        var settings = new AppSettings();
+
+        Assert.Equal(AnchorSide.BottomRight, settings.AtCursor.Side);
+        Assert.Equal(16, settings.AtCursor.Offset);
+        Assert.Equal(CaretSide.Right, settings.AtCaret.Side);
+        Assert.Equal(16, settings.AtCaret.Offset);
+
+        // The middle of the monitor, where there is no edge to stand off from
+        Assert.Equal(ScreenPosition.Center, settings.FixedPoint.Position);
+        Assert.Equal(0, settings.FixedPoint.Offset);
+
+        PopupModeSettings[] modes = [settings.AtCursor, settings.AtCaret, settings.FixedPoint];
+
+        Assert.All(modes, mode =>
+        {
+            Assert.Equal(20, mode.FontSize);
+            Assert.Equal(0.9, mode.Opacity);
+            Assert.Equal(Color.FromArgb(0x20, 0x20, 0x20), mode.BackgroundColor);
+            Assert.Equal(Color.FromArgb(0xFF, 0xFF, 0xFF), mode.ForegroundColor);
+        });
+
+        // Three modes and three sets of settings: none of them is shared
+        Assert.Equal(3, modes.Distinct().Count());
+    }
+
+    [Theory]
+    [InlineData(PopupPlacementMode.AtCursor)]
+    [InlineData(PopupPlacementMode.AtCaret)]
+    [InlineData(PopupPlacementMode.FixedPoint)]
+    public void The_chosen_mode_is_the_one_handed_out(PopupPlacementMode mode)
+    {
+        var settings = new AppSettings { PlacementMode = mode };
+
+        PopupModeSettings expected = mode switch
+        {
+            PopupPlacementMode.AtCaret => settings.AtCaret,
+            PopupPlacementMode.FixedPoint => settings.FixedPoint,
+            _ => settings.AtCursor,
+        };
+
+        Assert.Same(expected, settings.Current);
+    }
+
+    /// <summary>
+    /// The settings of a mode are its own: setting one up leaves the others alone.
+    /// </summary>
+    /// <remarks>
+    /// This is the whole point of keeping them per mode. A look shared by the modes
+    /// meant setting it up again after every switch, and switching modes to see what
+    /// they do undid what had just been set up.
+    /// </remarks>
+    [Fact]
+    public void Setting_one_mode_up_leaves_the_others_where_they_were()
+    {
+        var settings = new AppSettings();
+
+        settings.AtCaret.FontSize = 12;
+        settings.AtCaret.Side = CaretSide.Left;
+        settings.AtCaret.BackgroundColor = Color.FromArgb(0x11, 0x22, 0x33);
+
+        Assert.Equal(20, settings.AtCursor.FontSize);
+        Assert.Equal(AnchorSide.BottomRight, settings.AtCursor.Side);
+        Assert.Equal(20, settings.FixedPoint.FontSize);
+        Assert.Equal(Color.FromArgb(0x20, 0x20, 0x20), settings.FixedPoint.BackgroundColor);
+    }
+
+    // The mode in force decides what the look means, so a switch of it is a change of
+    // everything the window shows through the current mode
+    [Fact]
+    public void A_switch_of_the_mode_is_announced_as_a_change_of_the_current_one()
+    {
+        var settings = new AppSettings();
+        List<string?> changed = [];
+        settings.PropertyChanged += (_, e) => changed.Add(e.PropertyName);
+
+        settings.PlacementMode = PopupPlacementMode.FixedPoint;
+
+        Assert.Contains(nameof(AppSettings.PlacementMode), changed);
+        Assert.Contains(nameof(AppSettings.Current), changed);
+    }
+
+    /// <summary>
+    /// A change inside a mode is passed on as a change of the settings.
+    /// </summary>
+    /// <remarks>
+    /// The service that writes the file listens to the settings alone. Without this, a
+    /// font size dragged in the window would never reach the disk.
+    /// </remarks>
+    [Fact]
+    public void A_change_inside_a_mode_is_announced_by_the_settings()
+    {
+        var settings = new AppSettings();
+        List<string?> changed = [];
+        settings.PropertyChanged += (_, e) => changed.Add(e.PropertyName);
+
+        settings.AtCaret.FontSize = 42;
+        settings.FixedPoint.Position = ScreenPosition.Bottom;
+        settings.AtCursor.Offset = 8;
+
+        Assert.Contains("AtCaret.FontSize", changed);
+        Assert.Contains("FixedPoint.Position", changed);
+        Assert.Contains("AtCursor.Offset", changed);
     }
 
     // The app must not change how the system behaves until it is asked to
@@ -82,8 +179,60 @@ public sealed class AppSettingsTests
         Assert.Empty(changed);
     }
 
-    // Duration and CapsLockHoldDelay are derived from other settings and have
-    // no business being in the file
+    /// <summary>
+    /// Pouring another instance in fills the modes in place rather than replacing them.
+    /// </summary>
+    /// <remarks>
+    /// This is the agent's side of the connection: the fresh values arrive as a freshly
+    /// parsed instance. Replacing the mode objects would leave the popup bound to the
+    /// old ones.
+    /// </remarks>
+    [Fact]
+    public void Taking_other_settings_over_fills_the_modes_that_are_already_there()
+    {
+        var settings = new AppSettings();
+        CursorModeSettings cursor = settings.AtCursor;
+
+        var other = new AppSettings
+        {
+            Language = "ru",
+            Theme = AppTheme.Dark,
+            PlacementMode = PopupPlacementMode.FixedPoint,
+            DurationMilliseconds = 900,
+            UseCapsLockHotkey = true,
+            CapsLockHoldMilliseconds = 450,
+        };
+
+        other.AtCursor.Side = AnchorSide.TopLeft;
+        other.AtCursor.Offset = 5;
+        other.AtCursor.FontSize = 11;
+        other.AtCaret.Side = CaretSide.Left;
+        other.AtCaret.ForegroundColor = Color.FromArgb(0x0A, 0x0B, 0x0C);
+        other.FixedPoint.Position = ScreenPosition.Top;
+        other.FixedPoint.Offset = 64;
+
+        settings.CopyFrom(other);
+
+        Assert.Same(cursor, settings.AtCursor);
+
+        Assert.Equal("ru", settings.Language);
+        Assert.Equal(AppTheme.Dark, settings.Theme);
+        Assert.Equal(PopupPlacementMode.FixedPoint, settings.PlacementMode);
+        Assert.Equal(900, settings.DurationMilliseconds);
+        Assert.True(settings.UseCapsLockHotkey);
+        Assert.Equal(450, settings.CapsLockHoldMilliseconds);
+
+        Assert.Equal(AnchorSide.TopLeft, settings.AtCursor.Side);
+        Assert.Equal(5, settings.AtCursor.Offset);
+        Assert.Equal(11, settings.AtCursor.FontSize);
+        Assert.Equal(CaretSide.Left, settings.AtCaret.Side);
+        Assert.Equal(Color.FromArgb(0x0A, 0x0B, 0x0C), settings.AtCaret.ForegroundColor);
+        Assert.Equal(ScreenPosition.Top, settings.FixedPoint.Position);
+        Assert.Equal(64, settings.FixedPoint.Offset);
+    }
+
+    // Derived values and the modes handed out for convenience are computed from what
+    // is stored and have no business being in the file themselves
     [Fact]
     public void Derived_values_stay_out_of_the_file()
     {
@@ -93,10 +242,14 @@ public sealed class AppSettingsTests
 
         Assert.DoesNotContain(nameof(AppSettings.Duration), names);
         Assert.DoesNotContain(nameof(AppSettings.CapsLockHoldDelay), names);
+        Assert.DoesNotContain(nameof(AppSettings.Current), names);
 
         // What they are derived from, on the other hand, has to be stored
         Assert.Contains(nameof(AppSettings.DurationMilliseconds), names);
         Assert.Contains(nameof(AppSettings.CapsLockHoldMilliseconds), names);
+        Assert.Contains(nameof(AppSettings.AtCursor), names);
+        Assert.Contains(nameof(AppSettings.AtCaret), names);
+        Assert.Contains(nameof(AppSettings.FixedPoint), names);
     }
 
     [Fact]
@@ -118,6 +271,11 @@ public sealed class AppSettingsTests
     }
 
     /// <summary>Names of the settings the user is able to change.</summary>
+    /// <remarks>
+    /// The modes are handed out rather than assigned — they are filled in place — so
+    /// they are not among these. What is inside them is checked by
+    /// <see cref="PopupModeSettingsTests"/>.
+    /// </remarks>
     internal static IEnumerable<string> WritablePropertyNames() =>
         typeof(AppSettings).GetProperties()
             .Where(property => property.CanWrite)

CursorLang.Core.Tests/Models/PopupModeSettingsTests.cs

@@ -0,0 +1,289 @@
+using System.ComponentModel;
+using System.Drawing;
+using System.Reflection;
+using System.Text.Json;
+using CursorLang.Core.Models;
+
+namespace CursorLang.Core.Tests.Models;
+
+/// <summary>
+/// The settings of a single placement mode: what the popup looks like there and how
+/// far from its anchor it sits.
+/// </summary>
+public sealed class PopupModeSettingsTests
+{
+    [Fact]
+    public void The_cursor_mode_starts_out_below_and_right_of_the_pointer()
+    {
+        var mode = new CursorModeSettings();
+
+        Assert.Equal(AnchorSide.BottomRight, mode.Side);
+        Assert.Equal(16, mode.Offset);
+    }
+
+    /// <summary>
+    /// Next to the caret the popup goes beside it, and to the right by default.
+    /// </summary>
+    /// <remarks>
+    /// Above or below the caret is where the next line of the text is, so those sides
+    /// are not on offer at all — the type has the two of them and no more.
+    /// </remarks>
+    [Fact]
+    public void The_caret_mode_starts_out_to_the_right_of_the_caret()
+    {
+        var mode = new CaretModeSettings();
+
+        Assert.Equal(CaretSide.Right, mode.Side);
+        Assert.Equal(16, mode.Offset);
+        Assert.Equal([CaretSide.Left, CaretSide.Right], Enum.GetValues<CaretSide>());
+    }
+
+    [Theory]
+    [InlineData(CaretSide.Left, AnchorSide.Left)]
+    [InlineData(CaretSide.Right, AnchorSide.Right)]
+    public void The_side_of_the_caret_lines_the_popup_up_with_it(CaretSide side, AnchorSide expected)
+    {
+        var mode = new CaretModeSettings { Side = side };
+
+        Assert.Equal(expected, mode.Anchor);
+    }
+
+    [Fact]
+    public void A_changed_side_of_the_caret_is_a_change_of_what_it_lines_up_with()
+    {
+        var mode = new CaretModeSettings();
+        List<string?> changed = [];
+        mode.PropertyChanged += (_, e) => changed.Add(e.PropertyName);
+
+        mode.Side = CaretSide.Left;
+
+        Assert.Contains(nameof(CaretModeSettings.Anchor), changed);
+    }
+
+    /// <summary>
+    /// The fixed point starts out in the middle of the monitor, where there is no edge
+    /// to stand off from.
+    /// </summary>
+    [Fact]
+    public void The_fixed_point_starts_out_in_the_middle_with_no_offset()
+    {
+        var mode = new FixedPointModeSettings();
+
+        Assert.Equal(ScreenPosition.Center, mode.Position);
+        Assert.Equal(0, mode.Offset);
+        Assert.False(mode.IsAtAnEdge);
+    }
+
+    // A setting that is not shown must not be one that still applies
+    [Fact]
+    public void Moving_the_fixed_point_to_the_middle_drops_the_offset()
+    {
+        var mode = new FixedPointModeSettings { Position = ScreenPosition.TopLeft, Offset = 40 };
+
+        Assert.True(mode.IsAtAnEdge);
+
+        mode.Position = ScreenPosition.Center;
+
+        Assert.Equal(0, mode.Offset);
+        Assert.False(mode.IsAtAnEdge);
+    }
+
+    [Theory]
+    [InlineData(ScreenPosition.TopLeft)]
+    [InlineData(ScreenPosition.Top)]
+    [InlineData(ScreenPosition.TopRight)]
+    [InlineData(ScreenPosition.BottomLeft)]
+    [InlineData(ScreenPosition.Bottom)]
+    [InlineData(ScreenPosition.BottomRight)]
+    public void Away_from_the_middle_the_offset_is_kept(ScreenPosition position)
+    {
+        var mode = new FixedPointModeSettings { Position = position, Offset = 40 };
+
+        Assert.Equal(40, mode.Offset);
+        Assert.True(mode.IsAtAnEdge);
+    }
+
+    [Fact]
+    public void A_changed_place_of_the_fixed_point_is_a_change_of_having_an_edge()
+    {
+        var mode = new FixedPointModeSettings();
+        List<string?> changed = [];
+        mode.PropertyChanged += (_, e) => changed.Add(e.PropertyName);
+
+        mode.Position = ScreenPosition.Bottom;
+
+        Assert.Contains(nameof(FixedPointModeSettings.IsAtAnEdge), changed);
+    }
+
+    [Theory]
+    [MemberData(nameof(WritableProperties), typeof(CursorModeSettings))]
+    [MemberData(nameof(WritableProperties), typeof(CaretModeSettings))]
+    [MemberData(nameof(WritableProperties), typeof(FixedPointModeSettings))]
+    public void A_changed_setting_is_announced_to_subscribers(Type type, string propertyName)
+    {
+        PopupModeSettings mode = Create(type);
+        List<string?> changed = [];
+        mode.PropertyChanged += (_, e) => changed.Add(e.PropertyName);
+
+        SetDifferentValue(mode, propertyName);
+
+        Assert.Contains(propertyName, changed);
+    }
+
+    [Theory]
+    [MemberData(nameof(WritableProperties), typeof(CursorModeSettings))]
+    [MemberData(nameof(WritableProperties), typeof(CaretModeSettings))]
+    [MemberData(nameof(WritableProperties), typeof(FixedPointModeSettings))]
+    public void Writing_the_same_value_leaves_subscribers_alone(Type type, string propertyName)
+    {
+        PopupModeSettings mode = Create(type);
+        PropertyInfo property = type.GetProperty(propertyName)!;
+
+        List<string?> changed = [];
+        mode.PropertyChanged += (_, e) => changed.Add(e.PropertyName);
+
+        property.SetValue(mode, property.GetValue(mode));
+
+        Assert.Empty(changed);
+    }
+
+    [Fact]
+    public void The_cursor_mode_takes_another_one_over_whole()
+    {
+        var mode = new CursorModeSettings();
+        var other = new CursorModeSettings
+        {
+            Side = AnchorSide.Left,
+            Offset = 3,
+            FontSize = 41,
+            Opacity = 0.25,
+            BackgroundColor = Color.FromArgb(0x01, 0x02, 0x03),
+            ForegroundColor = Color.FromArgb(0x04, 0x05, 0x06),
+        };
+
+        mode.CopyFrom(other);
+
+        Assert.Equal(AnchorSide.Left, mode.Side);
+        Assert.Equal(3, mode.Offset);
+        Assert.Equal(41, mode.FontSize);
+        Assert.Equal(0.25, mode.Opacity);
+        Assert.Equal(Color.FromArgb(0x01, 0x02, 0x03), mode.BackgroundColor);
+        Assert.Equal(Color.FromArgb(0x04, 0x05, 0x06), mode.ForegroundColor);
+    }
+
+    [Fact]
+    public void The_caret_mode_takes_another_one_over_whole()
+    {
+        var mode = new CaretModeSettings();
+        var other = new CaretModeSettings { Side = CaretSide.Left, Offset = 2, FontSize = 15 };
+
+        mode.CopyFrom(other);
+
+        Assert.Equal(CaretSide.Left, mode.Side);
+        Assert.Equal(2, mode.Offset);
+        Assert.Equal(15, mode.FontSize);
+    }
+
+    [Fact]
+    public void The_fixed_point_takes_another_one_over_whole()
+    {
+        var mode = new FixedPointModeSettings();
+        var other = new FixedPointModeSettings
+        {
+            Position = ScreenPosition.Bottom,
+            Offset = 120,
+            FontSize = 60,
+            Opacity = 0.5,
+            BackgroundColor = Color.FromArgb(0x07, 0x08, 0x09),
+            ForegroundColor = Color.FromArgb(0x0A, 0x0B, 0x0C),
+        };
+
+        mode.CopyFrom(other);
+
+        Assert.Equal(ScreenPosition.Bottom, mode.Position);
+        Assert.Equal(120, mode.Offset);
+        Assert.Equal(60, mode.FontSize);
+        Assert.Equal(0.5, mode.Opacity);
+        Assert.Equal(Color.FromArgb(0x07, 0x08, 0x09), mode.BackgroundColor);
+        Assert.Equal(Color.FromArgb(0x0A, 0x0B, 0x0C), mode.ForegroundColor);
+    }
+
+    // Taking over a mode that sits in the middle takes its lack of an offset over too
+    [Fact]
+    public void Taking_over_a_fixed_point_in_the_middle_leaves_no_offset()
+    {
+        var mode = new FixedPointModeSettings { Position = ScreenPosition.Top, Offset = 32 };
+
+        mode.CopyFrom(new FixedPointModeSettings());
+
+        Assert.Equal(ScreenPosition.Center, mode.Position);
+        Assert.Equal(0, mode.Offset);
+    }
+
+    // What a mode works out from what it stores is not stored itself
+    [Fact]
+    public void Derived_values_of_a_mode_stay_out_of_the_file()
+    {
+        List<string> caret = Stored(new CaretModeSettings());
+        List<string> fixedPoint = Stored(new FixedPointModeSettings());
+
+        Assert.DoesNotContain(nameof(CaretModeSettings.Anchor), caret);
+        Assert.DoesNotContain(nameof(FixedPointModeSettings.IsAtAnEdge), fixedPoint);
+
+        Assert.Contains(nameof(CaretModeSettings.Side), caret);
+        Assert.Contains(nameof(FixedPointModeSettings.Position), fixedPoint);
+    }
+
+    [Fact]
+    public void A_mode_reports_changes_as_INotifyPropertyChanged()
+    {
+        Assert.IsAssignableFrom<INotifyPropertyChanged>(new CursorModeSettings());
+        Assert.IsAssignableFrom<INotifyPropertyChanged>(new CaretModeSettings());
+        Assert.IsAssignableFrom<INotifyPropertyChanged>(new FixedPointModeSettings());
+    }
+
+    public static TheoryData<Type, string> WritableProperties(Type type)
+    {
+        var data = new TheoryData<Type, string>();
+
+        foreach (string name in WritablePropertyNames(type))
+        {
+            data.Add(type, name);
+        }
+
+        return data;
+    }
+
+    /// <summary>Names of the settings of a mode the user is able to change.</summary>
+    internal static IEnumerable<string> WritablePropertyNames(Type type) =>
+        type.GetProperties().Where(property => property.CanWrite).Select(property => property.Name);
+
+    private static PopupModeSettings Create(Type type) => (PopupModeSettings)Activator.CreateInstance(type)!;
+
+    private static List<string> Stored<TMode>(TMode mode) where TMode : PopupModeSettings
+    {
+        using JsonDocument document = JsonSerializer.SerializeToDocument(mode);
+
+        return [.. document.RootElement.EnumerateObject().Select(property => property.Name)];
+    }
+
+    // A value guaranteed to differ from the current one: each kind of setting has its
+    // own way of differing
+    private static void SetDifferentValue(PopupModeSettings mode, string propertyName)
+    {
+        PropertyInfo property = mode.GetType().GetProperty(propertyName)!;
+
+        object next = property.GetValue(mode) switch
+        {
+            double number => number + 1,
+            Color color => Color.FromArgb((byte)(color.R + 1), color.G, color.B),
+            Enum value => Enum.GetValues(value.GetType())
+                .Cast<object>()
+                .First(other => !Equals(other, value)),
+
+            var other => throw new NotSupportedException($"Unknown kind of setting: {other?.GetType()}"),
+        };
+
+        property.SetValue(mode, next);
+    }
+}

CursorLang.Core.Tests/Resources/StringsTests.cs

@@ -108,6 +108,11 @@ public sealed class StringsTests
             data.Add(key);
         }
 
+        foreach (string key in EnumKeysOf<CaretSide>())
+        {
+            data.Add(key);
+        }
+
         foreach (string key in EnumKeysOf<ScreenPosition>())
         {
             data.Add(key);

CursorLang.Core.Tests/Services/CapsLockSwitchCoordinatorTests.cs

@@ -71,7 +71,7 @@ public sealed class CapsLockSwitchCoordinatorTests
         int startsBefore = hotkey.StartCalls;
         int stopsBefore = hotkey.StopCalls;
 
-        settings.FontSize = 44;
+        settings.Current.FontSize = 44;
         settings.CapsLockHoldMilliseconds = 700;
 
         Assert.Equal(startsBefore, hotkey.StartCalls);

CursorLang.Core.Tests/Services/SettingsServiceTests.cs

@@ -30,7 +30,7 @@ public sealed class SettingsServiceTests
         });
 
         Assert.Equal(AppTheme.System, settings.Theme);
-        Assert.Equal(20, settings.FontSize);
+        Assert.Equal(20, settings.Current.FontSize);
     }
 
     [Theory]
@@ -72,10 +72,10 @@ public sealed class SettingsServiceTests
             using SettingsService service = Create(folder);
             AppSettings settings = service.Load();
 
-            settings.FontSize = 42;
             settings.Theme = AppTheme.Dark;
             settings.PlacementMode = PopupPlacementMode.AtCaret;
-            settings.BackgroundColor = Color.FromArgb(0x11, 0x22, 0x33);
+            settings.Current.FontSize = 42;
+            settings.Current.BackgroundColor = Color.FromArgb(0x11, 0x22, 0x33);
             settings.UseCapsLockHotkey = true;
 
             service.Save();
@@ -87,10 +87,10 @@ public sealed class SettingsServiceTests
             return service.Load();
         });
 
-        Assert.Equal(42, restored.FontSize);
+        Assert.Equal(42, restored.Current.FontSize);
         Assert.Equal(AppTheme.Dark, restored.Theme);
         Assert.Equal(PopupPlacementMode.AtCaret, restored.PlacementMode);
-        Assert.Equal(Color.FromArgb(0x11, 0x22, 0x33), restored.BackgroundColor);
+        Assert.Equal(Color.FromArgb(0x11, 0x22, 0x33), restored.Current.BackgroundColor);
         Assert.True(restored.UseCapsLockHotkey);
     }
 
@@ -104,7 +104,7 @@ public sealed class SettingsServiceTests
             using SettingsService service = Create(folder);
             AppSettings settings = service.Load();
             settings.Theme = AppTheme.Dark;
-            settings.BackgroundColor = Color.FromArgb(0x20, 0x20, 0x20);
+            settings.Current.BackgroundColor = Color.FromArgb(0x20, 0x20, 0x20);
             service.Save();
         });
 
@@ -130,7 +130,7 @@ public sealed class SettingsServiceTests
             AppSettings settings = service.Load();
             service.TrackChanges();
 
-            settings.FontSize = 33;
+            settings.Current.FontSize = 33;
 
             // Right after the edit there is nothing on disk yet: the write is deferred
             Assert.False(File.Exists(path));
@@ -156,7 +156,7 @@ public sealed class SettingsServiceTests
 
             for (int i = 0; i < 10; i++)
             {
-                settings.Opacity = 0.5 + (i * 0.01);
+                settings.Current.Opacity = 0.5 + (i * 0.01);
                 Assert.False(File.Exists(path));
                 Pump.Pause(TimeSpan.FromMilliseconds(10));
             }
@@ -188,7 +188,7 @@ public sealed class SettingsServiceTests
             service.TrackChanges();
 
             AppSettings settings = service.Load();
-            settings.FontSize = 29;
+            settings.Current.FontSize = 29;
 
             Pump.WaitFor(() => File.Exists(path), "the settings were written by the timer");
         });
@@ -230,11 +230,11 @@ public sealed class SettingsServiceTests
             using SettingsService service = Create(folder);
             AppSettings settings = service.Load();
 
-            File.WriteAllText(path, """{"FontSize": 31, "BackgroundColor": "#FF102030"}""");
+            File.WriteAllText(path, """{"AtCursor": {"FontSize": 31, "BackgroundColor": "#FF102030"}}""");
             service.Reload();
 
-            Assert.Equal(31, settings.FontSize);
-            Assert.Equal(Color.FromArgb(0x10, 0x20, 0x30), settings.BackgroundColor);
+            Assert.Equal(31, settings.Current.FontSize);
+            Assert.Equal(Color.FromArgb(0x10, 0x20, 0x30), settings.Current.BackgroundColor);
         });
     }
 
@@ -250,12 +250,12 @@ public sealed class SettingsServiceTests
         {
             using SettingsService service = Create(folder);
             AppSettings settings = service.Load();
-            settings.FontSize = 44;
+            settings.Current.FontSize = 44;
 
             File.WriteAllText(path, "not json at all");
             service.Reload();
 
-            Assert.Equal(44, settings.FontSize);
+            Assert.Equal(44, settings.Current.FontSize);
         });
     }
 
@@ -269,7 +269,7 @@ public sealed class SettingsServiceTests
             SettingsService service = Create(folder);
             AppSettings settings = service.Load();
             service.TrackChanges();
-            settings.FontSize = 27;
+            settings.Current.FontSize = 27;
 
             service.Dispose();
         });
@@ -295,7 +295,7 @@ public sealed class SettingsServiceTests
 
             string afterDispose = File.ReadAllText(path);
 
-            settings.FontSize = 99;
+            settings.Current.FontSize = 99;
             Pump.Pause(TimeSpan.FromMilliseconds(60));
 
             Assert.Equal(afterDispose, File.ReadAllText(path));
@@ -309,7 +309,7 @@ public sealed class SettingsServiceTests
         string inherited = folder.File("inherited.json");
         string own = folder.File("settings.json");
 
-        File.WriteAllText(inherited, """{"FontSize": 31, "Language": "ru"}""");
+        File.WriteAllText(inherited, """{"AtCursor": {"FontSize": 31}, "Language": "ru"}""");
 
         AppSettings settings = Pump.Run(() =>
         {
@@ -317,7 +317,7 @@ public sealed class SettingsServiceTests
             return service.Load();
         });
 
-        Assert.Equal(31, settings.FontSize);
+        Assert.Equal(31, settings.Current.FontSize);
         Assert.Equal("ru", settings.Language);
 
         // What was taken over is pinned to its new place at once rather than on the first edit
@@ -331,7 +331,7 @@ public sealed class SettingsServiceTests
     {
         using var folder = new TempFolder();
         string inherited = folder.File("inherited.json");
-        string original = """{"FontSize": 31}""";
+        string original = """{"AtCursor": {"FontSize": 31}}""";
 
         File.WriteAllText(inherited, original);
 
@@ -351,8 +351,8 @@ public sealed class SettingsServiceTests
         string own = folder.File("settings.json");
         string inherited = folder.File("inherited.json");
 
-        File.WriteAllText(own, """{"FontSize": 12}""");
-        File.WriteAllText(inherited, """{"FontSize": 31}""");
+        File.WriteAllText(own, """{"AtCursor": {"FontSize": 12}}""");
+        File.WriteAllText(inherited, """{"AtCursor": {"FontSize": 31}}""");
 
         AppSettings settings = Pump.Run(() =>
         {
@@ -360,7 +360,7 @@ public sealed class SettingsServiceTests
             return service.Load();
         });
 
-        Assert.Equal(12, settings.FontSize);
+        Assert.Equal(12, settings.Current.FontSize);
     }
 
     // Outside a package both paths are the same, so there is nothing to take over
@@ -392,14 +392,14 @@ public sealed class SettingsServiceTests
             return service.Load();
         });
 
-        Assert.Equal(20, settings.FontSize);
+        Assert.Equal(20, settings.Current.FontSize);
     }
 
     [Fact]
     public void Settings_with_unknown_fields_are_still_read()
     {
         using var folder = new TempFolder();
-        File.WriteAllText(folder.File("settings.json"), """{"FontSize": 15, "SomethingNew": true}""");
+        File.WriteAllText(folder.File("settings.json"), """{"AtCursor": {"FontSize": 15}, "SomethingNew": true}""");
 
         AppSettings settings = Pump.Run(() =>
         {
@@ -407,7 +407,7 @@ public sealed class SettingsServiceTests
             return service.Load();
         });
 
-        Assert.Equal(15, settings.FontSize);
+        Assert.Equal(15, settings.Current.FontSize);
     }
 
     [Theory]
@@ -417,7 +417,7 @@ public sealed class SettingsServiceTests
     public void A_colour_is_read_from_its_usual_notation(string stored, byte r, byte g, byte b)
     {
         using var folder = new TempFolder();
-        File.WriteAllText(folder.File("settings.json"), $$"""{"BackgroundColor": {{stored}}}""");
+        File.WriteAllText(folder.File("settings.json"), $$"""{"AtCursor": {"BackgroundColor": {{stored}} } }""");
 
         AppSettings settings = Pump.Run(() =>
         {
@@ -425,7 +425,7 @@ public sealed class SettingsServiceTests
             return service.Load();
         });
 
-        Assert.Equal(Color.FromArgb(r, g, b), settings.BackgroundColor);
+        Assert.Equal(Color.FromArgb(r, g, b), settings.Current.BackgroundColor);
     }
 
     [Theory]
@@ -435,7 +435,7 @@ public sealed class SettingsServiceTests
     public void An_unintelligible_colour_becomes_black(string stored)
     {
         using var folder = new TempFolder();
-        File.WriteAllText(folder.File("settings.json"), $$"""{"BackgroundColor": {{stored}}}""");
+        File.WriteAllText(folder.File("settings.json"), $$"""{"AtCursor": {"BackgroundColor": {{stored}} } }""");
 
         AppSettings settings = Pump.Run(() =>
         {
@@ -443,7 +443,7 @@ public sealed class SettingsServiceTests
             return service.Load();
         });
 
-        Assert.Equal(Color.Black, settings.BackgroundColor);
+        Assert.Equal(Color.Black, settings.Current.BackgroundColor);
     }
 
     // The service creates the settings folder itself
@@ -478,7 +478,7 @@ public sealed class SettingsServiceTests
             using SettingsService service = new(path, folder.File("inherited.json"), SaveDelay);
             AppSettings settings = service.Load();
 
-            settings.FontSize = 18;
+            settings.Current.FontSize = 18;
             service.Save();
         });
 
@@ -534,6 +534,107 @@ public sealed class SettingsServiceTests
         }
     }
 
+    // The modes are sections of their own, and every setting of a mode has to reach the
+    // file inside its own section
+    [Theory]
+    [InlineData(nameof(AppSettings.AtCursor), typeof(CursorModeSettings))]
+    [InlineData(nameof(AppSettings.AtCaret), typeof(CaretModeSettings))]
+    [InlineData(nameof(AppSettings.FixedPoint), typeof(FixedPointModeSettings))]
+    public void Every_setting_of_a_mode_reaches_its_section_of_the_file(string section, Type mode)
+    {
+        using var folder = new TempFolder();
+
+        Pump.Run(() =>
+        {
+            using SettingsService service = Create(folder);
+            _ = service.Load();
+            service.Save();
+        });
+
+        using JsonDocument document = JsonDocument.Parse(File.ReadAllText(folder.File("settings.json")));
+
+        Assert.True(document.RootElement.TryGetProperty(section, out JsonElement stored));
+
+        foreach (string name in PopupModeSettingsTests.WritablePropertyNames(mode))
+        {
+            Assert.True(stored.TryGetProperty(name, out _), $"{section}.{name}");
+        }
+    }
+
+    /// <summary>
+    /// The modes are stored apart: what is set up in one is still there after a trip
+    /// through the file and the other two.
+    /// </summary>
+    [Fact]
+    public void Each_mode_keeps_its_own_settings()
+    {
+        using var folder = new TempFolder();
+
+        Pump.Run(() =>
+        {
+            using SettingsService service = Create(folder);
+            AppSettings settings = service.Load();
+
+            settings.AtCursor.Side = AnchorSide.TopLeft;
+            settings.AtCursor.FontSize = 14;
+            settings.AtCaret.Side = CaretSide.Left;
+            settings.AtCaret.FontSize = 28;
+            settings.AtCaret.ForegroundColor = Color.FromArgb(0x0A, 0x0B, 0x0C);
+            settings.FixedPoint.Position = ScreenPosition.Top;
+            settings.FixedPoint.Offset = 96;
+            settings.FixedPoint.Opacity = 0.4;
+
+            service.Save();
+        });
+
+        AppSettings restored = Pump.Run(() =>
+        {
+            using SettingsService service = Create(folder);
+            return service.Load();
+        });
+
+        Assert.Equal(AnchorSide.TopLeft, restored.AtCursor.Side);
+        Assert.Equal(14, restored.AtCursor.FontSize);
+        Assert.Equal(CaretSide.Left, restored.AtCaret.Side);
+        Assert.Equal(28, restored.AtCaret.FontSize);
+        Assert.Equal(Color.FromArgb(0x0A, 0x0B, 0x0C), restored.AtCaret.ForegroundColor);
+        Assert.Equal(ScreenPosition.Top, restored.FixedPoint.Position);
+        Assert.Equal(96, restored.FixedPoint.Offset);
+        Assert.Equal(0.4, restored.FixedPoint.Opacity);
+
+        // What was left alone stays at its default rather than following a neighbour
+        Assert.Equal(0.9, restored.AtCursor.Opacity);
+    }
+
+    // A change inside a mode is a change of the settings: the file has to follow the
+    // sliders of the look as well as the ones above them
+    [Fact]
+    public void A_change_inside_a_mode_saves_itself()
+    {
+        using var folder = new TempFolder();
+        string path = folder.File("settings.json");
+
+        Pump.Run(() =>
+        {
+            using SettingsService service = Create(folder);
+            AppSettings settings = service.Load();
+            service.TrackChanges();
+
+            settings.AtCaret.FontSize = 37;
+
+            Pump.WaitFor(() => File.Exists(path), "the settings were written by the timer");
+        });
+
+        using JsonDocument document = JsonDocument.Parse(File.ReadAllText(path));
+
+        Assert.Equal(
+            37,
+            document.RootElement
+                .GetProperty(nameof(AppSettings.AtCaret))
+                .GetProperty(nameof(PopupModeSettings.FontSize))
+                .GetDouble());
+    }
+
     // An ordinary run picks the storage place itself: a package keeps settings
     // of its own, a separate install keeps them in the user profile
     [Fact]

CursorLang.Core/Models/AppSettings.cs

@@ -1,4 +1,4 @@
-using System.Drawing;
+using System.ComponentModel;
 using System.Text.Json.Serialization;
 using CommunityToolkit.Mvvm.ComponentModel;
 
@@ -8,11 +8,10 @@ namespace CursorLang.Core.Models;
 /// The application settings, as the settings window writes them to settings.json.
 /// </summary>
 /// <remarks>
-/// The colours are <see cref="System.Drawing.Color"/> rather than
-/// <c>System.Windows.Media.Color</c>. The former lives in System.Drawing.Primitives,
-/// which is part of the base runtime and brings neither WPF nor GDI+ along; the latter
-/// is WindowsBase, and this type is read by the agent, which must stay clear of it.
-/// The settings window turns them into brushes in its converters.
+/// Everything about the popup — the side, the offset, the font size, the opacity and
+/// both colours — belongs to a placement mode rather than to the application, and is
+/// kept in a <see cref="PopupModeSettings"/> of its own for each of them. So the
+/// settings of a mode are still there after a trip through the other two.
 ///
 /// Both processes hold an instance of this, but only the settings window writes: the
 /// agent re-reads the file and pours the fresh values into the instance it already has,
@@ -32,43 +31,6 @@ public sealed partial class AppSettings : ObservableObject
     [ObservableProperty]
     private PopupPlacementMode _placementMode = PopupPlacementMode.AtCursor;
 
-    // The side and the offset are stored per mode: the cursor and the caret call for
-    // different settings, and switching the mode does not reset them
-
-    /// <summary>The side of the cursor the popup is put on.</summary>
-    [ObservableProperty]
-    private AnchorSide _cursorSide = AnchorSide.BottomRight;
-
-    /// <summary>The offset from the cursor in WPF units.</summary>
-    [ObservableProperty]
-    private double _cursorOffset = 16;
-
-    /// <summary>The side of the caret the popup is put on.</summary>
-    [ObservableProperty]
-    private AnchorSide _caretSide = AnchorSide.BottomRight;
-
-    /// <summary>The offset from the caret in WPF units.</summary>
-    [ObservableProperty]
-    private double _caretOffset = 16;
-
-    /// <summary>
-    /// The place on the monitor for the <see cref="PopupPlacementMode.FixedPoint"/> mode.
-    /// </summary>
-    [ObservableProperty]
-    private ScreenPosition _screenPosition = ScreenPosition.BottomRight;
-
-    /// <summary>The offset from the monitor edge in WPF units.</summary>
-    [ObservableProperty]
-    private double _screenMargin = 24;
-
-    /// <summary>The size of the layout name in the popup, in WPF units.</summary>
-    [ObservableProperty]
-    private double _fontSize = 20;
-
-    /// <summary>The popup opacity: 1.0 is fully opaque.</summary>
-    [ObservableProperty]
-    private double _opacity = 0.9;
-
     /// <summary>How long the popup stays on screen, in milliseconds.</summary>
     [ObservableProperty]
     private double _durationMilliseconds = 500;
@@ -87,13 +49,44 @@ public sealed partial class AppSettings : ObservableObject
     [ObservableProperty]
     private double _capsLockHoldMilliseconds = 300;
 
-    /// <summary>The fill of the popup. The opacity is set by <see cref="Opacity"/>.</summary>
-    [ObservableProperty]
-    private Color _backgroundColor = Color.FromArgb(0xFF, 0x20, 0x20, 0x20);
+    public AppSettings()
+    {
+        AtCursor.PropertyChanged += OnModeChanged;
+        AtCaret.PropertyChanged += OnModeChanged;
+        FixedPoint.PropertyChanged += OnModeChanged;
+    }
 
-    /// <summary>The colour of the layout name in the popup.</summary>
-    [ObservableProperty]
-    private Color _foregroundColor = Color.FromArgb(0xFF, 0xFF, 0xFF, 0xFF);
+    /// <summary>The <see cref="PopupPlacementMode.AtCursor"/> mode.</summary>
+    /// <remarks>
+    /// The modes are handed out rather than replaced — the instance is the same for the
+    /// life of the settings, so a binding and a subscription to it hold. That is what
+    /// the creation handling is for: without it the deserializer would want a setter,
+    /// and reading the file would swap the object everything is bound to.
+    /// </remarks>
+    [JsonObjectCreationHandling(JsonObjectCreationHandling.Populate)]
+    public CursorModeSettings AtCursor { get; } = new();
+
+    /// <summary>The <see cref="PopupPlacementMode.AtCaret"/> mode.</summary>
+    [JsonObjectCreationHandling(JsonObjectCreationHandling.Populate)]
+    public CaretModeSettings AtCaret { get; } = new();
+
+    /// <summary>The <see cref="PopupPlacementMode.FixedPoint"/> mode.</summary>
+    [JsonObjectCreationHandling(JsonObjectCreationHandling.Populate)]
+    public FixedPointModeSettings FixedPoint { get; } = new();
+
+    /// <summary>The settings of the mode currently chosen.</summary>
+    /// <remarks>
+    /// The settings window binds the look through here, and the popup asks for it here
+    /// too: what is on screen is always the settings of the mode in force. A change of
+    /// <see cref="PlacementMode"/> announces this as changed, so the bindings follow.
+    /// </remarks>
+    [JsonIgnore]
+    public PopupModeSettings Current => PlacementMode switch
+    {
+        PopupPlacementMode.AtCaret => AtCaret,
+        PopupPlacementMode.FixedPoint => FixedPoint,
+        _ => AtCursor,
+    };
 
     /// <summary><see cref="DurationMilliseconds"/> as a <see cref="TimeSpan"/>.</summary>
     [JsonIgnore]
@@ -110,25 +103,43 @@ public sealed partial class AppSettings : ObservableObject
     /// <remarks>
     /// This is how the agent learns about an edit: the settings window is a separate
     /// process, so the fresh values arrive as a freshly parsed instance and are poured
-    /// into the one everything is already bound to, rather than replacing it.
+    /// into the one everything is already bound to, rather than replacing it. The modes
+    /// are filled the same way, and for the same reason.
     /// </remarks>
     public void CopyFrom(AppSettings other)
     {
         Language = other.Language;
         Theme = other.Theme;
         PlacementMode = other.PlacementMode;
-        CursorSide = other.CursorSide;
-        CursorOffset = other.CursorOffset;
-        CaretSide = other.CaretSide;
-        CaretOffset = other.CaretOffset;
-        ScreenPosition = other.ScreenPosition;
-        ScreenMargin = other.ScreenMargin;
-        FontSize = other.FontSize;
-        Opacity = other.Opacity;
         DurationMilliseconds = other.DurationMilliseconds;
         UseCapsLockHotkey = other.UseCapsLockHotkey;
         CapsLockHoldMilliseconds = other.CapsLockHoldMilliseconds;
-        BackgroundColor = other.BackgroundColor;
-        ForegroundColor = other.ForegroundColor;
+
+        AtCursor.CopyFrom(other.AtCursor);
+        AtCaret.CopyFrom(other.AtCaret);
+        FixedPoint.CopyFrom(other.FixedPoint);
     }
+
+    // The mode in force decides what the look means, so a switch of the mode is a
+    // change of everything bound through Current
+    partial void OnPlacementModeChanged(PopupPlacementMode value) => OnPropertyChanged(nameof(Current));
+
+    /// <summary>
+    /// Passes a change made inside a mode on as a change of the settings.
+    /// </summary>
+    /// <remarks>
+    /// A mode is an object of its own, so an edit in it is not an edit of this one as
+    /// far as <see cref="INotifyPropertyChanged"/> goes. The settings window binds
+    /// through the path and hears the mode itself, but the service that writes the file
+    /// listens to the settings alone — and without this a font size dragged in the
+    /// window would never reach the disk. The name says where the change happened:
+    /// "AtCaret.FontSize".
+    /// </remarks>
+    private void OnModeChanged(object? sender, PropertyChangedEventArgs e) =>
+        OnPropertyChanged($"{NameOfMode(sender)}.{e.PropertyName}");
+
+    private string NameOfMode(object? mode) =>
+        ReferenceEquals(mode, AtCaret) ? nameof(AtCaret)
+            : ReferenceEquals(mode, FixedPoint) ? nameof(FixedPoint)
+            : nameof(AtCursor);
 }

CursorLang.Core/Models/PopupModeSettings.cs

@@ -0,0 +1,141 @@
+using System.Drawing;
+using System.Text.Json.Serialization;
+using CommunityToolkit.Mvvm.ComponentModel;
+
+namespace CursorLang.Core.Models;
+
+/// <summary>
+/// The settings of one placement mode: where the popup goes and how it looks there.
+/// </summary>
+/// <remarks>
+/// Every mode keeps a set of its own. The popup next to the caret sits inside a text
+/// being read and is wanted small and quiet; the one in the corner of the monitor is
+/// looked for on purpose and is wanted large. A look shared by the modes meant setting
+/// it up again after every switch — and switching modes to see what they do undid what
+/// had just been set up.
+///
+/// The colours are <see cref="System.Drawing.Color"/> for the same reason as in
+/// <see cref="AppSettings"/>: the agent reads them and must stay clear of WPF.
+/// </remarks>
+public abstract partial class PopupModeSettings : ObservableObject
+{
+    /// <summary>The distance from whatever the popup is placed by, in WPF units.</summary>
+    [ObservableProperty]
+    private double _offset = 16;
+
+    /// <summary>The size of the layout name in the popup, in WPF units.</summary>
+    [ObservableProperty]
+    private double _fontSize = 20;
+
+    /// <summary>The popup opacity: 1.0 is fully opaque.</summary>
+    [ObservableProperty]
+    private double _opacity = 0.9;
+
+    /// <summary>The fill of the popup. The opacity is set by <see cref="Opacity"/>.</summary>
+    [ObservableProperty]
+    private Color _backgroundColor = Color.FromArgb(0xFF, 0x20, 0x20, 0x20);
+
+    /// <summary>The colour of the layout name in the popup.</summary>
+    [ObservableProperty]
+    private Color _foregroundColor = Color.FromArgb(0xFF, 0xFF, 0xFF, 0xFF);
+
+    /// <summary>
+    /// Takes the offset and the look of another mode over. What tells the modes apart —
+    /// the side, the place on the monitor — is copied by the mode itself.
+    /// </summary>
+    protected void CopyLookFrom(PopupModeSettings other)
+    {
+        Offset = other.Offset;
+        FontSize = other.FontSize;
+        Opacity = other.Opacity;
+        BackgroundColor = other.BackgroundColor;
+        ForegroundColor = other.ForegroundColor;
+    }
+}
+
+/// <summary>The mode that puts the popup next to the mouse cursor.</summary>
+public sealed partial class CursorModeSettings : PopupModeSettings
+{
+    /// <summary>The corner or the side of the cursor the popup is put on.</summary>
+    [ObservableProperty]
+    private AnchorSide _side = AnchorSide.BottomRight;
+
+    /// <summary>Takes the values of another mode of the same kind over.</summary>
+    public void CopyFrom(CursorModeSettings other)
+    {
+        CopyLookFrom(other);
+        Side = other.Side;
+    }
+}
+
+/// <summary>
+/// The mode that puts the popup next to the caret of the active input field.
+/// </summary>
+public sealed partial class CaretModeSettings : PopupModeSettings
+{
+    /// <summary>The side of the caret the popup is put on: only left or right.</summary>
+    [ObservableProperty]
+    private CaretSide _side = CaretSide.Right;
+
+    /// <summary>
+    /// The side as the layout arithmetic wants it. Both of them line the popup up with
+    /// the caret rather than putting it above or below.
+    /// </summary>
+    [JsonIgnore]
+    public AnchorSide Anchor => Side == CaretSide.Left ? AnchorSide.Left : AnchorSide.Right;
+
+    /// <summary>Takes the values of another mode of the same kind over.</summary>
+    public void CopyFrom(CaretModeSettings other)
+    {
+        CopyLookFrom(other);
+        Side = other.Side;
+    }
+
+    // The side decides what the popup is lined up against, so it is a change of that too
+    partial void OnSideChanged(CaretSide value) => OnPropertyChanged(nameof(Anchor));
+}
+
+/// <summary>
+/// The mode that puts the popup at a fixed place of the monitor holding the active
+/// window. Here <see cref="PopupModeSettings.Offset"/> is the distance from the edge
+/// of the monitor.
+/// </summary>
+/// <remarks>
+/// In the middle of the monitor there is no edge to keep a distance from, so the offset
+/// is zero there and the settings window does not offer it. Choosing the middle puts it
+/// back to zero rather than remembering it for later: a setting that is not shown must
+/// not be one that still applies.
+/// </remarks>
+public sealed partial class FixedPointModeSettings : PopupModeSettings
+{
+    /// <summary>The place on the monitor the popup is put at.</summary>
+    [ObservableProperty]
+    private ScreenPosition _position = ScreenPosition.Center;
+
+    public FixedPointModeSettings()
+    {
+        // The middle is the default, and it has no edge to stand off from
+        Offset = 0;
+    }
+
+    /// <summary>Whether the popup is put at an edge of the monitor rather than in its middle.</summary>
+    [JsonIgnore]
+    public bool IsAtAnEdge => Position != ScreenPosition.Center;
+
+    /// <summary>Takes the values of another mode of the same kind over.</summary>
+    public void CopyFrom(FixedPointModeSettings other)
+    {
+        CopyLookFrom(other);
+        Position = other.Position;
+    }
+
+    partial void OnPositionChanged(ScreenPosition value)
+    {
+        OnPropertyChanged(nameof(IsAtAnEdge));
+
+        if (value == ScreenPosition.Center)
+        {
+            Offset = 0;
+        }
+    }
+}

CursorLang.Core/Models/PopupPlacement.cs

@@ -19,7 +19,7 @@ public enum PopupPlacementMode
 }
 
 /// <summary>
-/// Which side of the cursor or the caret to show the popup on.
+/// Which side of the cursor to show the popup on.
 /// </summary>
 public enum AnchorSide
 {
@@ -31,6 +31,21 @@ public enum AnchorSide
     BottomRight,
 }
 
+/// <summary>
+/// Which side of the caret to show the popup on.
+/// </summary>
+/// <remarks>
+/// Only the two sides, unlike <see cref="AnchorSide"/>. The caret stands in a line of
+/// text being written, and above or below it is exactly where the next line is: the
+/// popup would cover what is being read. To the side it covers nothing, and the line
+/// it lines up with is the one the caret is in.
+/// </remarks>
+public enum CaretSide
+{
+    Left,
+    Right,
+}
+
 /// <summary>
 /// The place on the monitor for the <see cref="PopupPlacementMode.FixedPoint"/> mode.
 /// </summary>

CursorLang.Core/Resources/Strings.resx

@@ -121,6 +121,12 @@
   <data name="AnchorSide_Right" xml:space="preserve">
     <value>Right</value>
   </data>
+  <data name="CaretSide_Left" xml:space="preserve">
+    <value>Left</value>
+  </data>
+  <data name="CaretSide_Right" xml:space="preserve">
+    <value>Right</value>
+  </data>
   <data name="CursorOffsetLabel" xml:space="preserve">
     <value>Offset</value>
   </data>
@@ -151,6 +157,9 @@
   <data name="ScreenMarginLabel" xml:space="preserve">
     <value>Margin from screen edge</value>
   </data>
+  <data name="PopupLookPerModeHint" xml:space="preserve">
+    <value>The look below is remembered for the chosen placement mode alone.</value>
+  </data>
   <data name="FontSizeLabel" xml:space="preserve">
     <value>Font size</value>
   </data>

CursorLang.Core/Resources/Strings.ru.resx

@@ -121,6 +121,12 @@
   <data name="AnchorSide_Right" xml:space="preserve">
     <value>Справа</value>
   </data>
+  <data name="CaretSide_Left" xml:space="preserve">
+    <value>Слева</value>
+  </data>
+  <data name="CaretSide_Right" xml:space="preserve">
+    <value>Справа</value>
+  </data>
   <data name="CursorOffsetLabel" xml:space="preserve">
     <value>Отступ</value>
   </data>
@@ -151,6 +157,9 @@
   <data name="ScreenMarginLabel" xml:space="preserve">
     <value>Отступ от края экрана</value>
   </data>
+  <data name="PopupLookPerModeHint" xml:space="preserve">
+    <value>Оформление ниже запоминается только для выбранного режима.</value>
+  </data>
   <data name="FontSizeLabel" xml:space="preserve">
     <value>Размер шрифта</value>
   </data>

CursorLang.Settings.Tests/Services/ThemeServiceTests.cs

@@ -114,7 +114,7 @@ public sealed class ThemeServiceTests
         {
             using var service = new ThemeService(settings, static () => AppTheme.Dark);
 
-            settings.FontSize = 40;
+            settings.Current.FontSize = 40;
             settings.Language = "ru";
 
             Assert.Equal(AppTheme.Light, service.CurrentTheme);

CursorLang.Settings.Tests/ViewModels/SettingsViewModelTests.cs

@@ -43,7 +43,7 @@ public sealed class SettingsViewModelTests
         var localization = new FakeLocalizationService();
         using var viewModel = Create(settings, localization);
 
-        settings.FontSize = 30;
+        settings.Current.FontSize = 30;
 
         Assert.Equal("en", localization.CurrentLanguage);
     }
@@ -59,6 +59,18 @@ public sealed class SettingsViewModelTests
         Assert.Equal(Enum.GetValues<ScreenPosition>(), viewModel.ScreenPositions.Select(option => option.Value));
     }
 
+    // Next to the caret the popup only goes beside it: above or below is where the next
+    // line of the text is
+    [Fact]
+    public void The_caret_is_offered_two_sides_and_no_more()
+    {
+        using SettingsViewModel viewModel = Create();
+
+        Assert.Equal(
+            [CaretSide.Left, CaretSide.Right],
+            viewModel.CaretSides.Select(option => option.Value));
+    }
+
     // A caption key is built from the type name and the value
     [Fact]
     public void The_option_captions_come_from_the_resources()
@@ -85,6 +97,7 @@ public sealed class SettingsViewModelTests
         Assert.Same(first, viewModel.Themes[0]);
         Assert.Equal("ru:AppTheme_System", first.Display);
         Assert.Equal("ru:AnchorSide_TopLeft", viewModel.AnchorSides[0].Display);
+        Assert.Equal("ru:CaretSide_Left", viewModel.CaretSides[0].Display);
         Assert.Equal("ru:ScreenPosition_TopLeft", viewModel.ScreenPositions[0].Display);
         Assert.Equal("ru:PopupPlacementMode_AtCursor", viewModel.PlacementModes[0].Display);
     }
@@ -114,8 +127,8 @@ public sealed class SettingsViewModelTests
         var settings = new AppSettings();
         using var viewModel = Create(settings);
 
-        Assert.Contains(settings.BackgroundColor, viewModel.BackgroundPalette);
-        Assert.Contains(settings.ForegroundColor, viewModel.TextPalette);
+        Assert.Contains(settings.Current.BackgroundColor, viewModel.BackgroundPalette);
+        Assert.Contains(settings.Current.ForegroundColor, viewModel.TextPalette);
     }
 
     [Fact]

CursorLang.Settings.Tests/Views/MainWindowTests.cs

@@ -124,7 +124,8 @@ public sealed class MainWindowTests
     {
         Sta.Run(() =>
         {
-            var settings = new AppSettings { FontSize = 33 };
+            var settings = new AppSettings();
+            settings.Current.FontSize = 33;
             using SettingsViewModel viewModel = CreateViewModel(settings);
 
             Open(viewModel, window =>
@@ -133,6 +134,178 @@ public sealed class MainWindowTests
         });
     }
 
+    /// <summary>
+    /// The preview follows the mode: switching it shows the settings of the new one.
+    /// </summary>
+    /// <remarks>
+    /// The look is bound through the current mode, so a switch has to reach the window.
+    /// Bound to a mode by name, the sliders would keep showing the cursor mode whatever
+    /// was chosen above them.
+    /// </remarks>
+    [Fact]
+    public void A_switch_of_the_mode_shows_the_settings_of_that_mode()
+    {
+        Sta.Run(() =>
+        {
+            var settings = new AppSettings();
+            settings.AtCursor.FontSize = 24;
+            settings.FixedPoint.FontSize = 56;
+
+            using SettingsViewModel viewModel = CreateViewModel(settings);
+
+            Open(viewModel, window =>
+            {
+                Assert.Contains(FindAll<TextBlock>(window), text => Math.Abs(text.FontSize - 24) < 0.001);
+
+                settings.PlacementMode = PopupPlacementMode.FixedPoint;
+                window.UpdateLayout();
+
+                Assert.Contains(FindAll<TextBlock>(window), text => Math.Abs(text.FontSize - 56) < 0.001);
+            });
+        });
+    }
+
+    /// <summary>
+    /// In the middle of the monitor the offset from the edge cannot be set, but it stays
+    /// in place.
+    /// </summary>
+    /// <remarks>
+    /// There is no edge to stand off from there, so the setting goes grey. Taking the row
+    /// out of the section instead would move everything below it on every switch of the
+    /// place — the section is not to jump about.
+    /// </remarks>
+    [Fact]
+    public void In_the_middle_of_the_monitor_the_offset_from_the_edge_goes_grey()
+    {
+        Sta.Run(() =>
+        {
+            var settings = new AppSettings { PlacementMode = PopupPlacementMode.FixedPoint };
+            using SettingsViewModel viewModel = CreateViewModel(settings);
+
+            Open(viewModel, window =>
+            {
+                Slider offset = Assert.Single(FindSlidersBoundTo(window, "Settings.FixedPoint.Offset"));
+
+                Assert.True(offset.IsVisible);
+                Assert.False(offset.IsEnabled);
+
+                // And it looks the part: the template draws from brushes that know
+                // nothing of the state, so the style has to fade it
+                Assert.True(offset.Opacity < 1);
+
+                settings.FixedPoint.Position = ScreenPosition.TopRight;
+                window.UpdateLayout();
+
+                Assert.True(offset.IsVisible);
+                Assert.True(offset.IsEnabled);
+                Assert.Equal(1, offset.Opacity);
+
+                settings.FixedPoint.Position = ScreenPosition.Center;
+                window.UpdateLayout();
+
+                Assert.True(offset.IsVisible);
+                Assert.False(offset.IsEnabled);
+                Assert.True(offset.Opacity < 1);
+            });
+        });
+    }
+
+    // Another mode has no fixed point at all, and its offset has no place on screen
+    [Fact]
+    public void Away_from_the_fixed_point_its_offset_is_not_shown()
+    {
+        Sta.Run(() =>
+        {
+            var settings = new AppSettings { PlacementMode = PopupPlacementMode.AtCursor };
+            using SettingsViewModel viewModel = CreateViewModel(settings);
+
+            Open(viewModel, window =>
+                Assert.All(FindSlidersBoundTo(window, "Settings.FixedPoint.Offset"), slider =>
+                    Assert.False(slider.IsVisible)));
+        });
+    }
+
+    /// <summary>
+    /// What the look belongs to is explained in a tooltip next to the mode.
+    /// </summary>
+    /// <remarks>
+    /// The sliders of the look show other numbers after a switch of the mode, and that
+    /// has to be explained. A line of text saying so would sit in the section forever,
+    /// while the question is asked once.
+    /// </remarks>
+    [Fact]
+    public void The_window_explains_that_the_look_belongs_to_the_mode()
+    {
+        Sta.Run(() =>
+        {
+            using SettingsViewModel viewModel = CreateViewModel();
+
+            Open(viewModel, window =>
+            {
+                // The text of a tooltip is bound but not computed until the tooltip is
+                // shown, so what it is bound to is what gets checked
+                List<TextBlock> hints =
+                [
+                    .. FindAll<TextBlock>(window)
+                        .Where(text => text.ToolTip is ToolTip tip &&
+                            tip.Content is TextBlock content &&
+                            PathOf(content, TextBlock.TextProperty) == "Localization[PopupLookPerModeHint]"),
+                ];
+
+                TextBlock link = Assert.Single(hints);
+
+                Assert.Equal("en:MoreInfoLink", link.Text);
+                Assert.True(link.IsVisible);
+            });
+        });
+    }
+
+    // Beside the caret and nowhere else: the list offers the two sides it has
+    [Fact]
+    public void The_caret_is_offered_two_sides_in_the_window()
+    {
+        Sta.Run(() =>
+        {
+            var settings = new AppSettings { PlacementMode = PopupPlacementMode.AtCaret };
+            using SettingsViewModel viewModel = CreateViewModel(settings);
+
+            Open(viewModel, window =>
+            {
+                ComboBox sides = Assert.Single(
+                    FindAll<ComboBox>(window),
+                    box => BindingOperations.GetBinding(box, Selector.SelectedValueProperty)?.Path.Path
+                        == "Settings.AtCaret.Side");
+
+                Assert.Equal(2, sides.Items.Count);
+
+                sides.SelectedValue = CaretSide.Left;
+
+                Assert.Equal(CaretSide.Left, settings.AtCaret.Side);
+            });
+        });
+    }
+
+    // The sliders of the look write into the mode chosen above them
+    [Fact]
+    public void The_look_is_edited_in_the_mode_that_is_chosen()
+    {
+        Sta.Run(() =>
+        {
+            var settings = new AppSettings { PlacementMode = PopupPlacementMode.AtCaret };
+            using SettingsViewModel viewModel = CreateViewModel(settings);
+
+            Open(viewModel, window =>
+            {
+                Slider slider = Assert.Single(FindSlidersBoundTo(window, "Settings.Current.FontSize"));
+
+                slider.Value = 44;
+
+                Assert.Equal(44, settings.AtCaret.FontSize);
+                Assert.Equal(20, settings.AtCursor.FontSize);
+            });
+        });
+    }
+
     [Fact]
     public void The_tooltip_colours_are_shown_as_swatches()
     {
@@ -144,7 +317,7 @@ public sealed class MainWindowTests
             // The chosen colour is shown as a swatch with a caption — in the
             // same notation the settings file uses
             System.Drawing.Color chosen = viewModel.BackgroundPalette[2];
-            settings.BackgroundColor = chosen;
+            settings.Current.BackgroundColor = chosen;
 
             string expected = $"#{chosen.R:X2}{chosen.G:X2}{chosen.B:X2}";
 
@@ -359,6 +532,13 @@ public sealed class MainWindowTests
         FindAll<Button>(root).Where(button =>
             BindingOperations.GetBinding(button, ButtonBase.CommandProperty)?.Path.Path == path);
 
+    private static string? PathOf(DependencyObject element, DependencyProperty property) =>
+        BindingOperations.GetBinding(element, property)?.Path.Path;
+
+    private static IEnumerable<Slider> FindSlidersBoundTo(DependencyObject root, string path) =>
+        FindAll<Slider>(root).Where(slider =>
+            BindingOperations.GetBinding(slider, RangeBase.ValueProperty)?.Path.Path == path);
+
     private static IEnumerable<CheckBox> FindStartupCheckBoxes(DependencyObject root) =>
         FindCheckBoxesBoundTo(root, nameof(SettingsViewModel.RunAtStartup));
 

CursorLang.Settings/Themes/Controls.xaml

@@ -337,6 +337,11 @@
                 </ControlTemplate>
             </Setter.Value>
         </Setter>
+        <Style.Triggers>
+            <Trigger Property="IsEnabled" Value="False">
+                <Setter Property="Opacity" Value="0.5" />
+            </Trigger>
+        </Style.Triggers>
     </Style>
 
     <!-- ======================= ProgressBar ======================= -->

CursorLang.Settings/ViewModels/SettingsViewModel.cs

@@ -87,6 +87,7 @@ public sealed partial class SettingsViewModel : ObservableObject, IDisposable
         Themes = CreateOptions<AppTheme>();
         PlacementModes = CreateOptions<PopupPlacementMode>();
         AnchorSides = CreateOptions<AnchorSide>();
+        CaretSides = CreateOptions<CaretSide>();
         ScreenPositions = CreateOptions<ScreenPosition>();
     }
 
@@ -107,6 +108,9 @@ public sealed partial class SettingsViewModel : ObservableObject, IDisposable
 
     public IReadOnlyList<EnumOption<AnchorSide>> AnchorSides { get; }
 
+    /// <summary>The sides on offer next to the caret: there the popup only goes beside it.</summary>
+    public IReadOnlyList<EnumOption<CaretSide>> CaretSides { get; }
+
     public IReadOnlyList<EnumOption<ScreenPosition>> ScreenPositions { get; }
 
     /// <summary>Whether to show the startup setting.</summary>
@@ -187,6 +191,7 @@ public sealed partial class SettingsViewModel : ObservableObject, IDisposable
         Translate(Themes);
         Translate(PlacementModes);
         Translate(AnchorSides);
+        Translate(CaretSides);
         Translate(ScreenPositions);
     }
 

CursorLang.Settings/Views/MainWindow.xaml

@@ -39,6 +39,11 @@
             <!-- The caption column is narrow, and a translation may not fit into it:
                  such a caption is better wrapped onto a second line than cut off -->
             <Setter Property="TextWrapping" Value="Wrap" />
+            <Style.Triggers>
+                <Trigger Property="IsEnabled" Value="False">
+                    <Setter Property="Opacity" Value="0.5" />
+                </Trigger>
+            </Style.Triggers>
         </Style>
         <Style TargetType="TextBlock" x:Key="FieldValue">
             <Setter Property="VerticalAlignment" Value="Center" />
@@ -46,6 +51,11 @@
             <Setter Property="MinWidth" Value="48" />
             <Setter Property="TextAlignment" Value="Right" />
             <Setter Property="Foreground" Value="{DynamicResource Theme.SecondaryForeground}" />
+            <Style.Triggers>
+                <Trigger Property="IsEnabled" Value="False">
+                    <Setter Property="Opacity" Value="0.5" />
+                </Trigger>
+            </Style.Triggers>
         </Style>
     </Window.Resources>
 
@@ -282,8 +292,24 @@
                             <RowDefinition Height="Auto" />
                         </Grid.RowDefinitions>
 
-                        <TextBlock Style="{StaticResource FieldLabel}"
-                                   Text="{Binding Localization[PlacementModeLabel]}" />
+                        <TextBlock Style="{StaticResource FieldLabel}">
+                            <Run Text="{Binding Localization[PlacementModeLabel], Mode=OneWay}" />
+                            <InlineUIContainer BaselineAlignment="Baseline">
+                                <TextBlock Text="{Binding Localization[MoreInfoLink]}"
+                                           Foreground="{DynamicResource Theme.Accent}"
+                                           TextDecorations="Underline"
+                                           Cursor="Help"
+                                           ToolTipService.InitialShowDelay="200"
+                                           ToolTipService.ShowDuration="60000">
+                                    <TextBlock.ToolTip>
+                                        <ToolTip>
+                                            <TextBlock TextWrapping="Wrap" MaxWidth="320"
+                                                       Text="{Binding Localization[PopupLookPerModeHint]}" />
+                                        </ToolTip>
+                                    </TextBlock.ToolTip>
+                                </TextBlock>
+                            </InlineUIContainer>
+                        </TextBlock>
                         <ComboBox Grid.Column="1" Grid.ColumnSpan="2"
                                   ItemsSource="{Binding PlacementModes}"
                                   ItemTemplate="{StaticResource EnumOptionTemplate}"
@@ -301,7 +327,7 @@
                                   ItemsSource="{Binding AnchorSides}"
                                   ItemTemplate="{StaticResource EnumOptionTemplate}"
                                   SelectedValuePath="Value"
-                                  SelectedValue="{Binding Settings.CursorSide}"
+                                  SelectedValue="{Binding Settings.AtCursor.Side}"
                                   Visibility="{Binding Settings.PlacementMode,
                                       Converter={StaticResource EnumToVisibility},
                                       ConverterParameter=AtCursor}" />
@@ -314,13 +340,13 @@
                                        ConverterParameter=AtCursor}" />
                         <Slider Grid.Row="2" Grid.Column="1" Margin="0,12,0,0"
                                 Minimum="0" Maximum="80" TickFrequency="1"
-                                Value="{Binding Settings.CursorOffset}"
+                                Value="{Binding Settings.AtCursor.Offset}"
                                 Visibility="{Binding Settings.PlacementMode,
                                     Converter={StaticResource EnumToVisibility},
                                     ConverterParameter=AtCursor}" />
                         <TextBlock Grid.Row="2" Grid.Column="2" Margin="12,12,0,0"
                                    Style="{StaticResource FieldValue}"
-                                   Text="{Binding Settings.CursorOffset, StringFormat={}{0:F0}}"
+                                   Text="{Binding Settings.AtCursor.Offset, StringFormat={}{0:F0}}"
                                    Visibility="{Binding Settings.PlacementMode,
                                        Converter={StaticResource EnumToVisibility},
                                        ConverterParameter=AtCursor}" />
@@ -333,10 +359,10 @@
                                        Converter={StaticResource EnumToVisibility},
                                        ConverterParameter=AtCaret}" />
                         <ComboBox Grid.Row="3" Grid.Column="1" Grid.ColumnSpan="2" Margin="0,12,0,0"
-                                  ItemsSource="{Binding AnchorSides}"
+                                  ItemsSource="{Binding CaretSides}"
                                   ItemTemplate="{StaticResource EnumOptionTemplate}"
                                   SelectedValuePath="Value"
-                                  SelectedValue="{Binding Settings.CaretSide}"
+                                  SelectedValue="{Binding Settings.AtCaret.Side}"
                                   Visibility="{Binding Settings.PlacementMode,
                                       Converter={StaticResource EnumToVisibility},
                                       ConverterParameter=AtCaret}" />
@@ -349,13 +375,13 @@
                                        ConverterParameter=AtCaret}" />
                         <Slider Grid.Row="4" Grid.Column="1" Margin="0,12,0,0"
                                 Minimum="0" Maximum="80" TickFrequency="1"
-                                Value="{Binding Settings.CaretOffset}"
+                                Value="{Binding Settings.AtCaret.Offset}"
                                 Visibility="{Binding Settings.PlacementMode,
                                     Converter={StaticResource EnumToVisibility},
                                     ConverterParameter=AtCaret}" />
                         <TextBlock Grid.Row="4" Grid.Column="2" Margin="12,12,0,0"
                                    Style="{StaticResource FieldValue}"
-                                   Text="{Binding Settings.CaretOffset, StringFormat={}{0:F0}}"
+                                   Text="{Binding Settings.AtCaret.Offset, StringFormat={}{0:F0}}"
                                    Visibility="{Binding Settings.PlacementMode,
                                        Converter={StaticResource EnumToVisibility},
                                        ConverterParameter=AtCaret}" />
@@ -371,7 +397,7 @@
                                   ItemsSource="{Binding ScreenPositions}"
                                   ItemTemplate="{StaticResource EnumOptionTemplate}"
                                   SelectedValuePath="Value"
-                                  SelectedValue="{Binding Settings.ScreenPosition}"
+                                  SelectedValue="{Binding Settings.FixedPoint.Position}"
                                   Visibility="{Binding Settings.PlacementMode,
                                       Converter={StaticResource EnumToVisibility},
                                       ConverterParameter=FixedPoint}" />
@@ -379,18 +405,21 @@
                         <TextBlock Grid.Row="6" Margin="0,12,12,0"
                                    Style="{StaticResource FieldLabel}"
                                    Text="{Binding Localization[ScreenMarginLabel]}"
+                                   IsEnabled="{Binding Settings.FixedPoint.IsAtAnEdge}"
                                    Visibility="{Binding Settings.PlacementMode,
                                        Converter={StaticResource EnumToVisibility},
                                        ConverterParameter=FixedPoint}" />
                         <Slider Grid.Row="6" Grid.Column="1" Margin="0,12,0,0"
                                 Minimum="0" Maximum="200" TickFrequency="1"
-                                Value="{Binding Settings.ScreenMargin}"
+                                Value="{Binding Settings.FixedPoint.Offset}"
+                                IsEnabled="{Binding Settings.FixedPoint.IsAtAnEdge}"
                                 Visibility="{Binding Settings.PlacementMode,
                                     Converter={StaticResource EnumToVisibility},
                                     ConverterParameter=FixedPoint}" />
                         <TextBlock Grid.Row="6" Grid.Column="2" Margin="12,12,0,0"
                                    Style="{StaticResource FieldValue}"
-                                   Text="{Binding Settings.ScreenMargin, StringFormat={}{0:F0}}"
+                                   Text="{Binding Settings.FixedPoint.Offset, StringFormat={}{0:F0}}"
+                                   IsEnabled="{Binding Settings.FixedPoint.IsAtAnEdge}"
                                    Visibility="{Binding Settings.PlacementMode,
                                        Converter={StaticResource EnumToVisibility},
                                        ConverterParameter=FixedPoint}" />
@@ -406,20 +435,20 @@
                                    Text="{Binding Localization[FontSizeLabel]}" />
                         <Slider Grid.Row="8" Grid.Column="1" Margin="0,12,0,0"
                                 Minimum="10" Maximum="72" TickFrequency="1"
-                                Value="{Binding Settings.FontSize}" />
+                                Value="{Binding Settings.Current.FontSize}" />
                         <TextBlock Grid.Row="8" Grid.Column="2" Margin="12,12,0,0"
                                    Style="{StaticResource FieldValue}"
-                                   Text="{Binding Settings.FontSize, StringFormat={}{0:F0}}" />
+                                   Text="{Binding Settings.Current.FontSize, StringFormat={}{0:F0}}" />
 
                         <TextBlock Grid.Row="9" Margin="0,12,12,0"
                                    Style="{StaticResource FieldLabel}"
                                    Text="{Binding Localization[OpacityLabel]}" />
                         <Slider Grid.Row="9" Grid.Column="1" Margin="0,12,0,0"
                                 Minimum="0.1" Maximum="1" TickFrequency="0.05"
-                                Value="{Binding Settings.Opacity}" />
+                                Value="{Binding Settings.Current.Opacity}" />
                         <TextBlock Grid.Row="9" Grid.Column="2" Margin="12,12,0,0"
                                    Style="{StaticResource FieldValue}"
-                                   Text="{Binding Settings.Opacity, StringFormat={}{0:P0}}" />
+                                   Text="{Binding Settings.Current.Opacity, StringFormat={}{0:P0}}" />
 
                         <TextBlock Grid.Row="10" Margin="0,12,12,0"
                                    Style="{StaticResource FieldLabel}"
@@ -427,7 +456,7 @@
                         <ComboBox Grid.Row="10" Grid.Column="1" Grid.ColumnSpan="2" Margin="0,12,0,0"
                                   ItemsSource="{Binding BackgroundPalette}"
                                   ItemTemplate="{StaticResource ColorSwatchTemplate}"
-                                  SelectedItem="{Binding Settings.BackgroundColor}" />
+                                  SelectedItem="{Binding Settings.Current.BackgroundColor}" />
 
                         <TextBlock Grid.Row="11" Margin="0,12,12,0"
                                    Style="{StaticResource FieldLabel}"
@@ -435,14 +464,11 @@
                         <ComboBox Grid.Row="11" Grid.Column="1" Grid.ColumnSpan="2" Margin="0,12,0,0"
                                   ItemsSource="{Binding TextPalette}"
                                   ItemTemplate="{StaticResource ColorSwatchTemplate}"
-                                  SelectedItem="{Binding Settings.ForegroundColor}" />
+                                  SelectedItem="{Binding Settings.Current.ForegroundColor}" />
 
                         <TextBlock Grid.Row="12" Margin="0,12,12,0"
                                    Style="{StaticResource FieldLabel}"
                                    Text="{Binding Localization[PreviewLabel]}" />
-                        <!-- The height of the area is sized for the largest font
-                             available: the sample text is fully visible at any
-                             position of the slider -->
                         <Border Grid.Row="12" Grid.Column="1" Grid.ColumnSpan="2"
                                 Margin="0,12,0,0" Padding="16"
                                 Height="152" ClipToBounds="True"
@@ -450,12 +476,12 @@
                                 HorizontalAlignment="Stretch">
                             <Border CornerRadius="4" Padding="10,4"
                                     HorizontalAlignment="Center" VerticalAlignment="Center"
-                                    Opacity="{Binding Settings.Opacity}"
-                                    Background="{Binding Settings.BackgroundColor,
+                                    Opacity="{Binding Settings.Current.Opacity}"
+                                    Background="{Binding Settings.Current.BackgroundColor,
                                         Converter={StaticResource ColorToBrush}}">
                                 <TextBlock Text="RU" FontWeight="SemiBold"
-                                           FontSize="{Binding Settings.FontSize}"
-                                           Foreground="{Binding Settings.ForegroundColor,
+                                           FontSize="{Binding Settings.Current.FontSize}"
+                                           Foreground="{Binding Settings.Current.ForegroundColor,
                                                Converter={StaticResource ColorToBrush}}" />
                             </Border>
                         </Border>

README.RU.md

@@ -143,6 +143,28 @@ MSIX всегда выполняются в контексте вошедшег
 быть установлены рядом, и приложение не вправе удалять настройки, которые ему не
 принадлежат.
 
+Всё, что относится к всплывающей подсказке, принадлежит режиму размещения, а не
+приложению, и файл хранит по разделу на каждый режим — `AtCursor`, `AtCaret` и
+`FixedPoint`. В каждом лежат сторона, отступ, размер шрифта, прозрачность и оба
+цвета. Подсказка рядом с курсором ввода находится внутри читаемого текста, и её
+хотят видеть небольшой и незаметной; ту, что в углу монитора, ищут намеренно, и её
+хотят видеть крупной. Общее для всех режимов оформление приходилось настраивать
+заново после каждого переключения, поэтому окно настроек показывает оформление
+выбранного выше режима и записывает только в него.
+
+Сторона означает в каждом режиме своё, и у каждого для неё собственный тип. Рядом с
+курсором мыши это любой из шести углов и сторон. Рядом с курсором ввода — только
+слева или справа: сверху и снизу от каретки находится следующая строка текста, и
+подсказка закрывала бы читаемое. Для фиксированной точки это место на мониторе, а
+отступ — расстояние от его края: в середине края нет, поэтому выбор середины
+сбрасывает отступ в нуль, а окно настроек показывает его неактивным. Отступ остаётся
+на месте, а не исчезает из раздела — появляющаяся и исчезающая строка сдвигала бы
+всё, что ниже, при каждой смене места.
+
+К какому режиму относится оформление, объясняет всплывающая подсказка рядом с самим
+режимом, а не строка текста в разделе: ползунки ниже показывают другие числа после
+переключения режима, и это вопрос, который задают один раз.
+
 ## Обновления
 
 Проверка выполняется при открытии окна настроек, а не при включении машины:

README.md

@@ -138,6 +138,28 @@ install and copies them over. The original file stays where it is: both builds
 may be installed side by side, and the app has no business deleting settings it
 does not own.
 
+Everything about the popup belongs to a placement mode rather than to the app, and
+the file keeps a section per mode — `AtCursor`, `AtCaret` and `FixedPoint`. Each of
+them holds the side, the offset, the font size, the opacity and both colours. The
+popup next to the caret sits inside a text being read and is wanted small and quiet;
+the one in the corner of the monitor is looked for on purpose and is wanted large. A
+look shared by the modes meant setting it up again after every switch, so the settings
+window shows the look of the mode chosen above it and writes into that mode alone.
+
+What the side means differs by mode, and each of them has a type saying so. Next to
+the cursor it is any of the six corners and sides. Next to the caret it is left or
+right and nothing else — above or below the caret is exactly where the next line of
+the text is, so the popup would cover what is being read. For the fixed point it is a
+place on the monitor, and the offset is the distance from its edge: in the middle
+there is no edge to stand off from, so choosing the middle puts the offset back to
+zero and the settings window shows it greyed out. It stays in place rather than
+leaving the section — a row that comes and goes would move everything below it on
+every switch of the place.
+
+Which mode the look belongs to is explained in a tooltip next to the mode itself
+rather than by a line of text in the section: the sliders below show other numbers
+after a switch of the mode, and that is a question asked once.
+
 ## Updates
 
 The check runs when the settings window is opened, not when the machine is