[Mesa-dev] [PATCH] egl_dri2: Allow both 24 and 32 bit X visuals for RGBA configs

[Ian Romanick]

I thought Eric and Chad already NAKed it in bugzilla.  The problem is
that applications ask for an RGBA visual for GL blending.  They use the
alpha channel to generate their images, but the final alpha values are,
basically, random... and the composited result would be pure garbage.

As Chad points out in comment #1, EGL just doesn't let applications do
the thing the patch is trying to do.

On 11/06/2014 05:12 AM, Emil Velikov wrote:
> Humble ping x2
> 
> On 14/10/14 15:25, Emil Velikov wrote:
>> Humble ping.
>>
>> On 23/09/14 01:25, Emil Velikov wrote:
>>> From: Sjoerd Simons <sjoerd.simons at collabora.co.uk>
>>>
>>> When using RGBA EGLConfigs allow both RGB and RGBA X visuals, such that
>>> application can decide whether they want to use RGBA (and have the
>>> compositor blend their windows).
>>>
>>> On my system with this change EGLConfigs with a 24 bit visual comes up
>>> first, as such applications blindly picking the first EGLConfig will
>>> still get an RGB X visual.
>>>
>>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=67676
>>> ---
>>>
>>> Hello gents,
>>>
>>> This patch has been stuck in bugzilla since February this year. Bringing 
>>> it around here to gather greater exposure and perhaps some 
>>> comments/reviews.
>>>
>>> -Emil
>>>
>>>  src/egl/drivers/dri2/egl_dri2.c     |  5 +++++
>>>  src/egl/drivers/dri2/platform_x11.c | 17 +++++++++--------
>>>  2 files changed, 14 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/src/egl/drivers/dri2/egl_dri2.c b/src/egl/drivers/dri2/egl_dri2.c
>>> index 20a7243..2ed90a7 100644
>>> --- a/src/egl/drivers/dri2/egl_dri2.c
>>> +++ b/src/egl/drivers/dri2/egl_dri2.c
>>> @@ -110,6 +110,11 @@ EGLint dri2_to_egl_attribute_map[] = {
>>>  static EGLBoolean
>>>  dri2_match_config(const _EGLConfig *conf, const _EGLConfig *criteria)
>>>  {
>>> +
>>> +   if (criteria->NativeVisualID != EGL_DONT_CARE &&
>>> +        conf->NativeVisualID != criteria->NativeVisualID)
>>> +      return EGL_FALSE;
>>> +
>>>     if (_eglCompareConfigs(conf, criteria, NULL, EGL_FALSE) != 0)
>>>        return EGL_FALSE;
>>>  
>>> diff --git a/src/egl/drivers/dri2/platform_x11.c b/src/egl/drivers/dri2/platform_x11.c
>>> index a7a7338..3395fb7 100644
>>> --- a/src/egl/drivers/dri2/platform_x11.c
>>> +++ b/src/egl/drivers/dri2/platform_x11.c
>>> @@ -672,14 +672,15 @@ dri2_x11_add_configs_for_visuals(struct dri2_egl_display *dri2_dpy,
>>>  	    dri2_add_config(disp, dri2_dpy->driver_configs[j], id++,
>>>  			    surface_type, config_attrs, rgba_masks);
>>>  
>>> -            /* Allow a 24-bit RGB visual to match a 32-bit RGBA EGLConfig.
>>> -             * Otherwise it will only match a 32-bit RGBA visual.  On a
>>> -             * composited window manager on X11, this will make all of the
>>> -             * EGLConfigs with destination alpha get blended by the
>>> -             * compositor.  This is probably not what the application
>>> -             * wants... especially on drivers that only have 32-bit RGBA
>>> -             * EGLConfigs! */
>>> -            if (d.data->depth == 24) {
>>> +            /* Allow both 24-bit RGB visual and 32 bit RGBA to match a 32-bit
>>> +             * RGBA EGLConfig.  Otherwise it will only match a 32-bit RGBA
>>> +             * visual.  On a composited window manager on X11, this will make
>>> +             * all of the EGLConfigs with destination alpha get blended by the
>>> +             * compositor.  This is probably not what the application wants...
>>> +             * especially on drivers that only have 32-bit RGBA EGLConfigs!
>>> +             * Allowing both allows applications to make the decision whether
>>> +             * 32 bit visuals are intended */
>>> +            if (d.data->depth == 24 || d.data->depth == 32) {
>>>                 rgba_masks[3] =
>>>                    ~(rgba_masks[0] | rgba_masks[1] | rgba_masks[2]);
>>>                 dri2_add_config(disp, dri2_dpy->driver_configs[j], id++,
>>>
>>
> 
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