Allow to set BackgroundColor of DocumentControl

src/Eto/Forms/ThemedControls/ThemedDocumentControlHandler.cs

@@ -21,6 +21,7 @@ public class ThemedDocumentControlHandler : ThemedContainerHandler<TableLayout,
 	Panel contentPanel;
 	Font font;
 
+	Color backgroundColor;
 	Color disabledForegroundColor;
 	Color closeBackgroundColor;
 	Color closeHighlightBackgroundColor;
@@ -75,6 +76,17 @@ public Font Font
 		}
 	}
 
+	/// <inheritdoc />
+	public override Color BackgroundColor
+	{
+		get => backgroundColor;
+		set
+		{
+			backgroundColor = value;
+			tabDrawable.Invalidate();
+		}
+	}
+
 	/// <summary>
 	/// Gets or sets the disabled foreground color.
 	/// </summary>
@@ -229,6 +241,7 @@ public ThemedDocumentControlHandler()
 		nextPrevWidth = 0;
 		startx = 0;
 		font = SystemFonts.Default();
+		backgroundColor = SystemColors.Control;
 		disabledForegroundColor = SystemColors.DisabledText;
 		closeBackgroundColor = SystemColors.Control;
 		closeHighlightBackgroundColor = SystemColors.Highlight;
@@ -596,7 +609,7 @@ void Drawable_Paint(object sender, PaintEventArgs e)
 	{
 		var g = e.Graphics;
 
-		g.Clear(SystemColors.Control);
+		g.Clear(BackgroundColor);
 
 		var posx = nextPrevWidth + startx;