Before this patch, we used legacy X11 xcursor names, and didn't really
have any fallback handling in place (we only tried to fallback to
"xterm", regardless of which cursor shape we were trying to load).
This patch changes two things:
1. Improved fallback support. cursor_shape_to_string() now returns a
list of strings. This allows us to have per-shape fallbacks, and any
number of fallbacks.
2. We prefer CSS xcursor names over legacy X11 names.
Using a lookup table, try to map the user-provided xcursor string to a
cursor-shape-v1 known shape.
If we succeed, set the user’s custom cursor using server side
cursors (i.e. using cursor-shape-v1).
If not, fallback to trying to load the image ourselves (using
wl_cursor_theme_get_cursor()), and set it using the legacy
wl_pointer_set_cursor().
This implements support for the new cursor-shape-v1 protocol. When
available, we use it, instead of client-side cursor surfaces, to
select the xcursor shape.
Note that we still need to keep client side pointers, for:
* backward compatibility
* to be able to "hide" the cursor
Closes#1379
