From: Aaron Jensen <aaronjensen@gmail.com>
Date: Tue, 18 Mar 2025 15:32:41 +0000
Cc: Gerd Möllmann <gerd.moellmann@gmail.com>, alan@idiocy.org, 77039@debbugs.gnu.org

Yes, redisplay should be a nop, since the buffer which is modified is not displayed.

But Aaron seems to say we keep comparing the glyph matrices of the window which is not show, something that should not happen, because we don't call update_frame on frames that are not visible.

I tried to explain that I wasn't convinced that it was that, that it could have, and even likely was, a redisplay of the currently displayed buffer (which is why *it* was flickering). Unless anyone thinks that there is reason to investigate further, I'm satisfied with the answer that reading process output can cause a comparison of glyphs, which is unlikely to result in a redisplay of an unrelated buffer.

Reading process output is not supposed to cause comparison of glyphs if the buffer to which process output is directed is not being displayed. So if you do see glyphs being compared in that case, we should look into that. The only glyphs that could be legitimately compared in that case are those on the mode line.