Issues with cursors (cursor-shape-v1)

[Campbell Barton]

Hi, I've been looking to support mouse cursors under wayland (via
cursor-shape-v1 but also more generally).

Attempting to use cursor-shape-v1, I ran into some mouse cursors not
being available, so I had to fallback to loading the "default" theme,
this might be OK however the cursor size used by cursor-shape-v1 isn't
known, so it can result in the cursor changing sizes within the same
application.

More generally not being able to know the preferred cursor size in
Wayland causes odd glitches, as the cursor size also changes between
applications, when LIBDECOR is used, the application and it's own
window decorations can use different cursor sizes too.

The same issue exists with themes, although I find it more noticeable
when the cursor size changes.

While accessing the preferred theme & size is possible it relies on
reading the settings for desktop environments (DBUS to read the GNOME
setting for e.g.).

It would be good if there was a way to access the cursor size & theme
via generic Wayland API's,
the size particularly so applications that use theme-cursors or define
their own cursor bitmaps can match the size of system cursors.

This could be implemented as part of cursor-shape-v1 although I'm not
sure if this is the appropriate level to expose the API.

-- 
- Campbell