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Xwayland/EGLstream remaining visual glitches

Even with !646 (merged), there are remaining visual glitches.

Initially, I reckoned that was a bug in Xwayland or in glamor, but I am not so sure now.

It all seems to behave as if there was multiple buffers involved and not all of them where successfully and consistently kept up-to-date.

Actually, it looks like double triple? buffering gone wrong to me (this is entirely empirical of course).

To reproduce:

  1. In xterm, open the menu (Ctrl+LMB)
  2. Navigate the menu
  3. Sometimes some past content show a few entries before the currently selected one

Alternate method:

  1. Resize xterm (or any other X11 window).
  2. Sometimes the whole window becomes black
  3. Typing in the window shows the different buffers.

I tried to capture a video of the issue:

eglstream

(quality is low because I tried to keep the file small)

We can see what looks like different buffers being updated as the cursor moved over the window - One of those buffers is fully updated, the other one has the character "a" typed and the rest is just black.

This is with GNOME Shell.

Edited by Olivier Fourdan
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