fix: focused window content disappearance in overview

[Weicao-CatilGrass]

On my system, when activating the Overview mode, the currently focused window disappears. This bug has also been reported by other users in issues (#207, #195).

When the Overview mode is activated, the focused window is being rendered simultaneously in two different locations:

1. In its original position on the workspace.
2. In the preview area within the Overview.

This leads to a rendering state conflict and issues with damage region calculation, causing the content of the original window to vanish.

My Solution
Replace the direct rendering of the window in the Overview with a rectangular placeholder. This avoids the conflicts arising from directly rendering the window object in two places.

2025-11-02_19-56-44.mp4

[marzeq]

Still glitches out with Firefox & Chromium

2025-11-18.15-39-21.mp4

[Weicao-CatilGrass]

Still glitches out with Firefox & Chromium
2025-11-18.15-39-21.mp4

Thanks for the feedback! This is a bit of a band-aid fix that works on my single-monitor setup but likely doesn't resolve the multi-monitor issue. I plan to address the root cause once I have a dual-monitor setup for testing.

[kgensou]

Thank you for patching! I've tried this patch with two monitors with different scaling, and it works fine for Firefox on my machine. Haven't seen any windows disappearing yet.

I do notice that while the top and left borders for the placeholder rectangle consistently render, the bottom and right borders are prone to flickering or not showing up at all. Still, that's a very minor issue compared to the main workspace window vanishing, so I'm sticking with this change.

[ryzendew]

could you rebase this please so i can test