changed settings saving (#3)

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

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