Distracting brightness "pulsing" with multi-tab windows when not selected

[dancrossnyc]

I'm afraid I lack the vocabulary to adequately describe this issue, so I apologize for the verbosity of this report; please bear with me. This has been happening for some time now, so it's not a new problem. I'm using the version built form nightly commits; currently I'm at 4eb5885 running on a Mac.

Suppose I create a Ghostty window, and in that window, split the window vertically. In one of the splits, I run some program that uses escape sequences to set colors, such as helix on some file that uses syntax highlighting. I then focus on the other pane, not running that program, and then change focus to some other window (such as the web browser window that I am typing this in).

Then If I look at the unselected, unfocused, pane in the Ghostty window, I will observe it seem to "pulse" as it cycles through several levels of brightness; it will progressively dim in stepped intervals at a rate of, maybe, two or three times a second until it hits some lower limit, and then pop back to full brightness; repeating continually. This can be very distracting, particularly since it often happens when the window is in one's peripheral vision.

Again, I apologize for the vagueness of this description; I'm attaching a video, taken with my phone, to this issue to try and illustrate what I mean. Searches for "brightness" and "dimming" didn't show anything that struck me as a dup, so additional apologies if this is a known issue.

GhosttyDimmingBrightness.mov

[taylrfnt]

I cannot reproduce this on tip - OP, can you please share the OS you're running on?

Edit: Missed the tag, I see it's MacOS

[taylrfnt]

Do you see this when inside a tui like vim or persistently across all Ghostty surfaces?

[dancrossnyc]

I see it on any window that uses any text attribute; for example, if I run man ls in a split, and section names are bolded, then the artifact appears and seems to remain, even after the program that does that has exited.

For instance, at the moment I have a window with two splits; both are only displaying the shell prompt, which uses no special visual effects, and the pulsing effect is evident in one.