When using the XShape APIs*, windows that have a rectangular shape are treated like normal windows (they get a title bar and shadow) even if the rectangular region is much smaller than the window.
When a non-rectangular window changes its shape to be rectangular, it gains a shadow that remains even after changing its shape back to be non-rectangular.
Ideally there would always be a shadow that matches the shape of the window.
In the mean time, the correct behavior might be to remove the shadow whenever a shape is applied. If the application wishes to remove an applied shape, they could do something like:
When using the XShape APIs*, windows that have a rectangular shape are treated like normal windows (they get a title bar and shadow) even if the rectangular region is much smaller than the window.
When a non-rectangular window changes its shape to be rectangular, it gains a shadow that remains even after changing its shape back to be non-rectangular.
Ideally there would always be a shadow that matches the shape of the window.
In the mean time, the correct behavior might be to remove the shadow whenever a shape is applied. If the application wishes to remove an applied shape, they could do something like:
XShapeCombine Mask(d, w, ShapeBounding, 0, 0, None, ShapeSet);
Please let me know if you need any more details, or if I'm missing something. (Unfortunately, the ubuntu-bug tool wouldn't work when filing this bug).
* http:// www.x.org/ releases/ current/ doc/xextproto/ shape.html