Previously, cases when a viewport source box was updated without attaching
a buffer weren't checked for correctness properly because the state's buffer
would be NULL. Use wlr_surface_state_has_buffer() instead.
According to the viewport protocol, upon wp_viewport::destroy():
> The associated wl_surface's crop and scale state is removed.
> The change is applied on the next wl_surface.commit.
Therefore, wp_viewport_destroy(viewport) should remove all viewport state.
Currently, wlroots does not remove the crop and scale state. Instead, a
client must do:
wl_fixed_t clear = wl_fixed_from_int(-1);
wp_viewport_set_source(viewport, clear, clear, clear, clear);
wp_viewport_set_destination(viewport, -1, -1);
wp_viewport_destroy(viewport);
This commit adds the necessary logic into viewport_destroy and makes
wlroots comply with the protocol.
Kirill Primak
Simon Ser
Alexander Orzechowski
Quantum