xdg-shell: Add edge constraints

An edge constraint is an complementery state to the tiled state, meaning that it's not only tiled, but constrained in a way that it can't resize in that direction.

This typically means that the constrained edge is tiled against a monitor edge. An example configuration is two windows tiled next to each other on a single monitor. Together they cover the whole work area.

The left window would have the following tiled and edge constraint state:

[ tiled_top, tiled_right, tiled_bottom, tiled_left, constrained_top, constrained_bottom, constrained_left ]

while the right window would have the following:

[ tiled_top, tiled_right, tiled_bottom, tiled_left, constrained_top, constrained_bottom, constrained_right ]

This aims to replace and deprecate the gtk_surface1.configure_edges event and the gtk_surface1.edge_constraint enum.

Signed-off-by: Jonas Ådahl jadahl@gmail.com

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• Review:
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• Acks:
  • GNOME (@jadahl)
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• Implementations:
  • mutter (https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3266)
  • gtk (https://gitlab.gnome.org/GNOME/gtk/-/merge_requests/6386)
  • N\A