fix bug - popup windows show hiding logic

CursorLang.Agent/Interop/GdiNative.cs

@@ -5,7 +5,7 @@ using CursorLang.Core.Interop;
 namespace CursorLang.Agent.Interop;
 
 /// <summary>
-/// Plain GDI: a font, a brush, a rounded region and text on a device context.
+/// Plain GDI: a font, text, and an off-screen bitmap to draw them into.
 /// </summary>
 /// <remarks>
 /// GDI rather than GDI+ on purpose. <c>System.Drawing.Common</c> would make the drawing
@@ -85,11 +85,41 @@ internal static class GdiNative
         int iCharSet, int iOutPrecision, int iClipPrecision, int iQuality, int iPitchAndFamily,
         string pszFaceName);
 
-    [DllImport("gdi32.dll")]
-    internal static extern IntPtr CreateSolidBrush(uint color);
+    /// <summary>
+    /// A 32-bit surface to draw the popup into before anyone can see it.
+    /// </summary>
+    /// <remarks>
+    /// Top-down — a negative height — so that the first row of <paramref name="bits"/>
+    /// is the top row of the picture and the alpha fixing up afterwards can walk the
+    /// memory straight through.
+    /// </remarks>
+    internal static IntPtr CreateSurface(IntPtr deviceContext, int width, int height, out IntPtr bits)
+    {
+        var header = new BitmapInfoHeader
+        {
+            biSize = Marshal.SizeOf<BitmapInfoHeader>(),
+            biWidth = width,
+            biHeight = -height,
+            biPlanes = 1,
+            biBitCount = 32,
+            biCompression = BI_RGB,
+        };
+
+        return CreateDIBSection(deviceContext, ref header, DIB_RGB_COLORS, out bits, IntPtr.Zero, 0);
+    }
+
+    private const uint BI_RGB = 0;
+    private const uint DIB_RGB_COLORS = 0;
 
     [DllImport("gdi32.dll")]
-    internal static extern IntPtr CreateRoundRectRgn(int x1, int y1, int x2, int y2, int w, int h);
+    internal static extern IntPtr CreateCompatibleDC(IntPtr hdc);
+
+    [DllImport("gdi32.dll")]
+    internal static extern bool DeleteDC(IntPtr hdc);
+
+    [DllImport("gdi32.dll")]
+    private static extern IntPtr CreateDIBSection(IntPtr hdc, ref BitmapInfoHeader header, uint usage,
+        out IntPtr bits, IntPtr section, uint offset);
 
     [DllImport("gdi32.dll")]
     internal static extern IntPtr SelectObject(IntPtr hdc, IntPtr h);
@@ -103,9 +133,6 @@ internal static class GdiNative
     [DllImport("gdi32.dll")]
     internal static extern uint SetTextColor(IntPtr hdc, uint color);
 
-    [DllImport("user32.dll")]
-    internal static extern int FillRect(IntPtr hdc, ref PopupWindowNative.Rect lprc, IntPtr hbr);
-
     [DllImport("user32.dll", CharSet = CharSet.Unicode, EntryPoint = "DrawTextW")]
     internal static extern int DrawText(IntPtr hdc, string lpchText, int cchText,
         ref PopupWindowNative.Rect lprc, uint format);
@@ -116,22 +143,19 @@ internal static class GdiNative
     [DllImport("user32.dll")]
     internal static extern int ReleaseDC(IntPtr hWnd, IntPtr hDC);
 
-    [DllImport("user32.dll")]
-    internal static extern IntPtr BeginPaint(IntPtr hWnd, out PaintStruct lpPaint);
-
-    [DllImport("user32.dll")]
-    internal static extern bool EndPaint(IntPtr hWnd, ref PaintStruct lpPaint);
-
     [StructLayout(LayoutKind.Sequential)]
-    internal struct PaintStruct
+    private struct BitmapInfoHeader
     {
-        public IntPtr hdc;
-        public bool fErase;
-        public PopupWindowNative.Rect rcPaint;
-        public bool fRestore;
-        public bool fIncUpdate;
-
-        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 32)]
-        public byte[] rgbReserved;
+        public int biSize;
+        public int biWidth;
+        public int biHeight;
+        public short biPlanes;
+        public short biBitCount;
+        public uint biCompression;
+        public uint biSizeImage;
+        public int biXPelsPerMeter;
+        public int biYPelsPerMeter;
+        public uint biClrUsed;
+        public uint biClrImportant;
     }
 }