Bug Report: Gaps or “holes” visible at window corners when using non-sharp decorations

I’ve noticed that when using non-sharp window decorations (like Slightly Round or Very Round) in Cosmic, especially with cosmic-terminal, there are small visible gaps or “holes” at the window corners. This is especially noticeable when a dark terminal is placed over a bright background (or when transparency is on).

It looks like the rounded corners aren’t fully filled, and some pixels remain unrendered or transparent.

Steps to reproduce:

1. Set window decoration to Slightly Round or Very Round.

2. Move the terminal around over a contrasting background.

3. Observe corners — small gaps may appear (especially at top-left/top-right).

Please consider reviewing how window corners are drawn in these decoration modes. This might be a minor rendering oversight but is quite visually distracting.

[jackpot51]

Is this specific to the terminal or are other applications affected?

is related to the terminal

[jackpot51]

Can you upload a screenshot of the issue?

[Donald42]

Is this specific to the terminal or are other applications affected?

I see the same thing in the text editor, too. The window border is square, but the window content is rounded, so there is a very tiny gap through which you can see the underlying window.

[git-f0x]

That's not an issue with apps. The compositor doesn't know the corner radius of windows, so the active hint can't be too round (to avoid covering content). The only options to fix that is for the compositor to clip windows to a specific corner radius (potentially cutting into content), or a wayland protocol for that to be developed.

Where there are gaps, however, is tabs (see #446), but could maybe be fixed by wrapping the tab bar in libcosmic in a container and adding a background color?

But this can likely be closed.

[TundraFox907]

This is likely the same issue I reported in cosmic-session#94.

Screenshots are provided below.

[jackpot51]

This is a cosmic-comp issue, one of these issues should be moved over and the rest closed as duplicates.

[git-f0x]

Yep, duplicate of pop-os/cosmic-comp#974.