XPLMWindowDecoration describes how “modern” windows will be displayed. This impacts both how X-Plane draws your window as well as certain mouse handlers.
|xplm_WindowDecorationNone||"0"||X-Plane will draw no decoration for your window, and apply no automatic click handlers. The window will not stop click from passing through its bounds. This is suitable for "windows" which request, say, the full screen bounds, then only draw in a small portion of the available area.|
|xplm_WindowDecorationRoundRectangle||"1"||The default decoration for "native" windows, like the map. Provides a solid background, as well as click handlers for resizing and dragging the window.|
|xplm_WindowDecorationSelfDecorated||"2"||X-Plane will draw no decoration for your window, nor will it provide resize handlers for your window edges, but it will stop clicks from passing through your windows bounds.|
|xplm_WindowDecorationSelfDecoratedResizable||"3"||Like self-decorated, but with resizing; X-Plane will draw no decoration for your window, but it will stop clicks from passing through your windows bounds, and provide automatic mouse handlers for resizing.|