[Wayland-bugs] [Bug 78190] protocol: Reporting damage in surface coordinates doesn't work with EGL

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=78190

--- Comment #2 from Pekka Paalanen <ppaalanen at gmail.com> ---
Jason, that is a very good analysis of the problems, and I agree with your
rationale.

If we choose to make damage in buffer coordinates, that will affect the
definition of the Presentation extension, and also the core protocol changes it
requires. Therefore Presentation cannot land until this issue is solved.

A fifth option came to my mind: keep all the Wayland semantics as is, but add a
function to wayland-egl API:

    void wl_egl_window_set_damage_size(struct wl_egl_window *egl_window, int
width, int height)

This call would set the damage rectangle, that eglSwapBuffers() normally uses,
and the size with which swapbuffers-with-damage uses to flip the rectangles.

It seems to me like this would solve the immediate issue.

However, I don't know if we can change the wayland-egl API at all. It has
absolutely no versioning, not on header level nor runtime. Build-time version
checks could be done by checking libwayland-client version for the header, and
the version reported by wayland-egl.pc (provided by the libwayland-egl.so
implementation) for the library version, but there is no way to check at
runtime.

<rant>
What's worse, wayland-egl.pc from Mesa reports the Mesa version. Any other EGL
implementation likely reports their own version, making the version vendor
dependent instead of API dependent. (The same problem applies to egl.pc, gl.pc,
glesv1_cm.pc and glesv2.pc.) I have no idea why these .pc files cannot just
report the real API version, e.g. EGL 1.4. If someone wants to check the
specific implementation's version, there should be an implementation-specific
.pc file for that, e.g. mesa3d.pc, since obviously the build is already
implementation dependent.
</rant>

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