Nested Hyprland worked but had real limits: the outer compositor decided
the nested window's pixel size (needing an outer-session float+resize
dispatch per capture), occluded surfaces got no frame callbacks (so grim
hung unless the nested window was also focused/raised), and there was no
way to fully suppress a brief real, visible flash of that window on the
operator's desktop.
wlroots' WLR_BACKENDS=headless (Sway, not Hyprland, is built on wlroots
directly) has a genuine headless backend: no seat/DRM-master claim, no
window anywhere, ever. Confirmed empirically: zero visible footprint,
both zwlr_layer_shell_v1 and zwlr_screencopy_manager_v1 present, grim
completes instantly with no focus dance needed.
This drops the Hyprland-specific plumbing that no longer applies:
- bread-screenshots now exposes one compositor-agnostic capture_region
primitive instead of capture_layer/capture_output, since the isolated
canvas size is always known up front rather than queried via hyprctl.
- bread-utils::hypr loses the Monitor scale/transform/logical_size and
Layer/find_layer additions that only existed to support that querying.
- bread-capture's isolation module spawns headless Sway instead of a
nested Hyprland instance, and passes --width/--height through to the
target app so it knows the canvas size without asking anyone.
Also fixes a socket leak in isolation teardown: killing the compositor
(Hyprland or Sway) doesn't unlink the wayland-N/.lock files it created,
so every capture run was orphaning a socket pair in the runtime dir.
Drop now removes them explicitly.
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