martin rudalics wrote:
> We should make sure that the bug happens with every pixelwise resize 
> operation, for example, when dragging the mode line between windows.

After evaluating

(setq window-resize-pixelwise t)

dragging the mode-line between windows triggers the bug.  I can see
the mode-line getting corrupt again and again, for brief moments[0],
while I move the mode-line over the window's lines, but after I
release the mouse button the mode-line gets redrawn and the glitch
isn't visible until I scroll the window somehow.


Footnotes:

[0] Only for brief moments because the mode-line is repainted after
each pixel boundary is crossed, in effect, fixing the mode-line.  This
is one evidence that Emacs *can do* something about this bug.

-- 
 ,= ,-_-. =.  Bruno Félix Rezende Ribeiro (oitofelix) [0x28D618AF]
((_/)o o(\_)) There is no system but GNU;
 `-'(. .)`-'  GNU Linux-Libre is one of its official kernels;
     \_/      All software must be free as in freedom;