[Mesa-dev] [PATCH] egl/wayland: Try to use wl_surface.damage_buffer for SwapBuffersWithDamage

[Derek Foreman]

On 12/02/16 04:46 PM, Emil Velikov wrote:
> On 11 February 2016 at 16:34, Derek Foreman <derekf at osg.samsung.com> wrote:
>> Since commit d1314de293e9e4a63c35f094c3893aaaed8580b4 we ignore
>> damage passed to SwapBuffersWithDamage.
>>
>> Wayland 1.10 now has functionality that allows us to properly
>> process those damage rectangles, and a way to query if it's
>> available.
>>
>> Now we can use wl_surface.damage_buffer and interpret the incoming
>> damage as being in buffer co-ordinates.
>>
>> Signed-off-by: Derek Foreman <derekf at osg.samsung.com>
>> ---
>>  src/egl/drivers/dri2/platform_wayland.c | 32 +++++++++++++++++++++++++++++---
>>  1 file changed, 29 insertions(+), 3 deletions(-)
>>
>> diff --git a/src/egl/drivers/dri2/platform_wayland.c b/src/egl/drivers/dri2/platform_wayland.c
>> index c2438f7..b5a5b59 100644
>> --- a/src/egl/drivers/dri2/platform_wayland.c
>> +++ b/src/egl/drivers/dri2/platform_wayland.c
>> @@ -653,6 +653,30 @@ create_wl_buffer(struct dri2_egl_surface *dri2_surf)
>>                            &wl_buffer_listener, dri2_surf);
>>  }
>>
>> +static EGLBoolean
>> +try_damage_buffer(struct dri2_egl_surface *dri2_surf,
>> +                  const EGLint *rects,
>> +                  EGLint n_rects)
>> +{
>> +#ifdef WL_SURFACE_DAMAGE_BUFFER_SINCE_VERSION
>> +   int i;
>> +
>> +   if (wl_proxy_get_version((struct wl_proxy *) dri2_surf->wl_win->surface)
>> +       < WL_SURFACE_DAMAGE_BUFFER_SINCE_VERSION)
>> +      return EGL_FALSE;
>> +
>> +   for (i = 0; i < n_rects; i++) {
>> +      const int *rect = &rects[i * 4];
>> +
>> +      wl_surface_damage_buffer(dri2_surf->wl_win->surface,
>> +                               rect[0],
>> +                               dri2_surf->base.Height - rect[1] - rect[3],
>> +                               rect[2], rect[3]);
>> +   }
>> +   return EGL_TRUE;
>> +#endif
> 
> I'm slightly worried about keeping this compile time. For example if
> we compile against old wayland, and then run against a capable one...
> this code won't exist thus will never get executed. Thus leading to a
> handful of "wtf" moments.
> 
> I would just ensure it's defined at the top.
> 
> #ifndef WL_SURFACE_DAMAGE_BUFFER_SINCE_VERSION
> #define WL_SURFACE_DAMAGE_BUFFER_SINCE_VERSION foo
> #endif

If your wayland headers don't have
WL_SURFACE_DAMAGE_BUFFER_SINCE_VERSION then compilation will fail
because wl_proxy_get_version() isn't present.

wl_proxy_get_version() will be formally introduced in the same wayland
release (next Tuesday's 1.10 release) as wl_surface_damage_buffer(), so
I'm intentionally using that as a tricky way to avoid the check
entirely.  Too tricky?

If you prefer I can work out some autoconfy stuff to determine if
wl_proxy_get_version() is available?

> Cheers,
> Emil
>