Clients draw the cursor image, they don't render it to the screen or blit it.
Basically, in the "old Wayland way", the Wayland compositor gave the client a surface and said "hey, draw something into this and I'll make it your cursor" and then the compositor well, composited it, using either true hardware cursor or an overlay layer of some kind. If the app froze, the cursor would still move, it just might not be updated. This seems clean architecturally but turns out to suck because now every client needs some kind of cursor drawing library in it, hopefully the same one everyone else is using so that cursor theming works and you don't get a different default mouse cursor in every app.
So then Wayland introduced wp_cursor_shape, which is where the client instead says "hey, draw a 'standard pointer' cursor over me please." But, the "old" client-drawn way is still supported and used, for example in GTK apps.
This proposal seems to just be a really complicated recommendation to change the file format used behind wp_cursor_shape, and a plea for "old" apps to either adopt this format/library or stop using client rendering. I think that switching to wp_cursor_shape pretty much Makes Sense for most apps, but the article didn't really sell me on this file format.
Basically, in the "old Wayland way", the Wayland compositor gave the client a surface and said "hey, draw something into this and I'll make it your cursor" and then the compositor well, composited it, using either true hardware cursor or an overlay layer of some kind. If the app froze, the cursor would still move, it just might not be updated. This seems clean architecturally but turns out to suck because now every client needs some kind of cursor drawing library in it, hopefully the same one everyone else is using so that cursor theming works and you don't get a different default mouse cursor in every app.
So then Wayland introduced wp_cursor_shape, which is where the client instead says "hey, draw a 'standard pointer' cursor over me please." But, the "old" client-drawn way is still supported and used, for example in GTK apps.
This proposal seems to just be a really complicated recommendation to change the file format used behind wp_cursor_shape, and a plea for "old" apps to either adopt this format/library or stop using client rendering. I think that switching to wp_cursor_shape pretty much Makes Sense for most apps, but the article didn't really sell me on this file format.