Currently, when the user is moving a window in the desktop grid it is drawn from the paintScreen function to ensure it appears above all other windows. However, when drawing the window, the screenProjectionMatrix for the WindowPaintData structure is never specified. Because of this, the window will not be visible if OpenGL compositing along with Lanczos scaling are in use since its coordinates will never be projected into screen-space (unless the window is maximized, in which case the scaling code is bypassed).
BUG: 361371
BUG: 364509
FIXED-IN: 5.14.3