Make allocator handle the swapchain managment

[bl4ckb0ne]

Another attempt to decouple the backend/renderer/output/swapchain

The allocator is now declared by the user, via either a call to wlr_allocator_autocreate or from a custom implementation.

The user has to set the allocator to the output, otherwise nothing will be displayed on screen.

The wlr_output is still using the wlr_renderer, but #3197 has good ideas to get rid of this.

Related to #3222 #3215 and #3197

[emersion]

Hm, I'm not sure what the upside to make the allocator responsible for creating the swapchain is. Can you elaborate?

It seems to me like doing this is making things more complicated instead of simplifying them. Before:

             renderer
                |
                v
allocator ->  output

After:

             renderer
                |
                v
allocator ->  output
    ^           |
    |           |
    +-----------+

[emersion]

"backend/multi: implement get_buffer_caps" looks good to me, pushed to master.

[bl4ckb0ne]

The motivation behind this little shift of responsability is to prevent the backend to instanciate its own renderer when using an external renderer. The current approache for an output to render is to get the allocator and renderer from its associated backend.

This patchset allows the user to provide its own allocator to the output, to avoid declaring multiple renderers.

There will be another patchset following this one to prevent the backends to create their allocator at creation.

[emersion]

wlroots has migrated to gitlab.freedesktop.org. This pull request has been moved to:

https://gitlab.freedesktop.org/wlroots/wlroots/-/merge_requests/3226