Fix: binding errors in Generic.xaml for VS2013 theme

[AhmadovMahammad]

Fix: Resolve XAML binding errors in VS2013 theme

Fixed XAML binding errors in Generic.xaml that were causing "Cannot find governing FrameworkElement" errors.
The issue occurred in the AnchorablePaneTitle and LayoutAnchorableFloatingWindowControl styles, where the GeometryDrawing
was using an ElementName binding to reference DragHandleGeometryPlaceholder's Fill property.

Solution: Replaced the element bindings with direct DynamicResource references to the same resource keys.

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The issue is caused in ./Themes/Generic.xaml in two styles:

1. <Style TargetType="avalonDockControls:AnchorablePaneTitle">
2. <Style x:Key="{x:Type avalonDockControls:LayoutAnchorableFloatingWindowControl}" TargetType="{x:Type avalonDockControls:LayoutAnchorableFloatingWindowControl}">

Both styles contain a GeometryDrawing element that attempts to bind to the Fill property of another element named "DragHandleGeometryPlaceholder" using an ElementName binding, which fails due to element relationship issues in the visual tree.

Solution

Fixed the problem by replacing the ElementName bindings with direct resource references:

Changed

<GeometryDrawing Brush="{Binding Fill, ElementName=DragHandleGeometryPlaceholder, Mode=OneWay, Converter={avalonDockConverters:NullToDoNothingConverter}}">

To:

<GeometryDrawing Brush="{DynamicResource {x:Static reskeys:ResourceKeys.ToolWindowCaptionInactiveGrip}}">

Testing

Tested with .NET 6 and VS2022
Confirmed binding errors no longer appear
Verified that theme styling appears correctly

[AhmadovMahammad]

ISSUE #377

[sharpSteff]

@AhmadovMahammad Thanks for the PR. Unfortunately the diff is too big too review (probably styling). Can you simplify it?

[sharpSteff]

diff too big