Visible scrollbar thumb, and icons that survive a theme switch

src/Stampeded/App.axaml

@@ -214,6 +214,19 @@
     <Style Selector="MenuItem">
       <Setter Property="ToolTip.ShowOnDisabled" Value="True" />
     </Style>
+    <!-- A scrollbar's thumb in a grey of its own. The Simple theme takes thumb and track from
+         two neighbouring palette brushes, which the quiet palette above leaves a shade apart -
+         and its pressed thumb is lighter than the track - so a list did not show that it
+         scrolls. Translucent, so the one grey stands out on the light track and the dark. -->
+    <Style Selector="ScrollBar /template/ Thumb#thumb">
+      <Setter Property="Background" Value="#70808080" />
+    </Style>
+    <Style Selector="ScrollBar /template/ Thumb#thumb:pointerover">
+      <Setter Property="Background" Value="#A0808080" />
+    </Style>
+    <Style Selector="ScrollBar /template/ Thumb#thumb:pressed">
+      <Setter Property="Background" Value="#C8808080" />
+    </Style>
     <Style Selector="OverlayPopupHost">
       <Setter Property="RenderTransformOrigin" Value="0%,0%" />
       <Setter Property="RenderTransform" Value="{x:Static local:ZoomState.PopupScale}" />

src/Stampeded/Images.cs

@@ -34,21 +34,28 @@ public static class Images
 	// every icon one that lifts that single colour and leaves the coloured parts alone.
 	const string DarkCss = "[fill=\"#202020\"] { fill: #D4D4D4; } [stroke=\"#202020\"] { stroke: #D4D4D4; }";
 
+	// The same rule restating the colour the icons already have. Not null: an SvgImage whose
+	// stylesheet is cleared falls back to the one its source was last loaded with, so an icon
+	// that has been dark once would stay light-on-light.
+	const string LightCss = "[fill=\"#202020\"] { fill: #202020; } [stroke=\"#202020\"] { stroke: #202020; }";
+
+	static string ThemeCss => Themes.ThemeManager.Current.IsDarkTheme ? DarkCss : LightCss;
+
 	static readonly List<SvgImage> loaded = [];
 
 	static Images()
 	{
 		Themes.ThemeManager.Current.ThemeChanged += (_, _) => {
 			foreach (var image in loaded)
-				image.Css = Themes.ThemeManager.Current.IsDarkTheme ? DarkCss : null;
+				image.Css = ThemeCss;
 		};
 	}
 
 	static IImage LoadSvg(string name)
 	{
 		var image = new SvgImage {
 			Source = SvgSource.Load(AssetBase + name + ".svg", null),
-			Css = Themes.ThemeManager.Current.IsDarkTheme ? DarkCss : null,
+			Css = ThemeCss,
 		};
 		loaded.Add(image);
 		return image;

src/Stampeded/ScreenshotWatcher.cs

@@ -480,6 +480,11 @@ public static void Attach(Window mainWindow)
 						App.Workspace?.NavigateToFileLineAsync(parts[1], gotoLine, oldSide: false, record: false).HandleExceptions();
 				}
 				var size = new Avalonia.PixelSize((int)window.Bounds.Width, (int)window.Bounds.Height);
+				// A command above may have invalidated layout in this same tick - a theme switch
+				// does, for every text block. Rendering before the layout pass draws a text block
+				// built from inlines as empty, and its run cache then keeps the empty result for
+				// good: the capture would not just show the blank rows, it would cause them.
+				window.UpdateLayout();
 				using var bitmap = new RenderTargetBitmap(size, new Avalonia.Vector(96, 96));
 				bitmap.Render(window);
 #pragma warning disable CS0618 // default PNG encoding is all this debug utility needs