[Bug]: Pixel wide gap between tiled windows in some circumstances

[Daxtorim]

Summary

In some circumstances there are small gaps between tiled windows or the edge of the working area. This results sometimes in unexpected behavior when moving focus with keyboard shortcuts as bismuth will no longer pick the last used window but instead goes for the window that happens to be one pixel closer.

Steps to Reproduce

1. Open a few windows
2. Switch layouts to """weird""" configurations
3. Observe gaps

It doesn't seem to be consistent in the sense that subsequent opposite actions don't result in the same outcome. By that I mean when the Three-Column-Layout has a gap, making the center one step larger, then immediately making it one step smaller again, essentially undoing the previous action, the gap might vanish.

I attached several screenshots you can try to replicate. From there just try to rotate parts or increase the size of windows or whatnot.

Sorry for not being able to provide exact steps.

Expected behavior

Tiled windows should be perfectly edge aligned and fill the entire working area without any gaps between them.

Screenshots

Bismuth version

master @ commit cc27485d1

KDE Plasma version

5.23.3

The platform KWin is running on

X11

Additional context

The native resolution of this laptop screen is 1366x768. Lower resolutions can make it even worse (see last screenshot (720x405) (edit: It looks worse since the pixels are bigger, it's still only one pixel, though)). Can't really test higher resolutions here.

[SuperSamus]

It seems that the gaps on the edge of the working can appear when resizing the windows. Also, gaps on the bottom and top edges of the screen can only appear when resizing vertically, and gaps on the left and right edges can only appear when resizing horizontally. These gaps don't exist when there is only one window to tile. The gaps are not only aesthetic: for example, the scroll bar on the right can normally be scrolled with the mouse on the far right, but not when there is that pixel gap. The issue is not fixed even by closing all windows of the working area (if you reopen them, the same gap will return even without resizing anything), and it also occurs on Wayland.