Discard fragments in cube shader
Discard fragments in grid shader

This prevents the depth buffer from being polluted with samples for
holes between grid lines.
Use glDepthMask instead of glDepthFunc

This allows us to correctly composite views with the 3D scene, while
still preventing collisions between two views.
Add depth buffer to XR views
Enable depth buffer
Add buffer type to zxr-shell-unstable-v1.xml

And update our implementation to consider it. This does not add a depth
buffer to wxrc, it just adds it to the state tracker for the XR shell
Rig up seat clipboard operations
Fix view_at logical view sorting

Should be done front-to-back and should exit early once a matching view
is found.
Add wlr-data-control and wp-primary-selection
Use logical distance for view_at

As opposed to spatial distance. We will likely want to change this later
for 3D views.
Implement resize with mod+right
Fix views setting NULL cursor
Implement scroll to move views in Z space
Merge branch 'zxr-shell'
Implement zxr-shell-unstable-v1
Source cursor images from clients
Send pointer events to child surfaces
Move child surface matrix computation to wxrc_view_get_2d_model_matrix
Render subsurfaces and popups