The popups used one Wayland layer surface per output sized to their content
(implicitWidth/Height bound to the toast column), so every time a toast was
added or removed the surface resized. During that resize the compositor
briefly scaled a stale buffer, stretching or squishing the cards mid-
transition -- worst with only one or two toasts, where each resize is a
larger relative change.
Make the surface full-screen and fixed, like the OSD overlay, so adding or
removing a toast only changes the content inside it and the surface never
resizes. Mask the input region to the toast column so the otherwise-
invisible full-screen overlay stays click-through.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
