[Mesa-dev] [PATCH] Make glXChooseFBConfig handle unspecified sRGB correctly

Jon Turney jon.turney at dronecode.org.uk
Sat Jul 14 14:24:14 UTC 2018

Make glXChooseFBConfig properly handle the case where the only matching
configs have the sRGB flag set, but no sRGB attribute is specified.

Since 6e06e281, the sRGBcapable flag is now actually compared, using

7b0f912e added defaulting of sRGBcapable to GL_FALSE in
__glXInitializeVisualConfigFromTags(), to handle servers which don't report
it, but this function is also used by glXChooseFBConfig(), so sRGBcapable is
implicitly false when not explicitly specified.

(This can cause e.g. glxinfo to fail to find anything matching the simple
config it looks for if all the candidates have the sRGB flag set to true.
I'm assuming this doesn't happen 'normally' as candidate configs with and
without sRGB true are available)

Move this defaulting to createConfigsFromProperties(), and set the default
for glXChooseFBConfig() in init_fbconfig_for_chooser() to GLX_DONT_CARE.
 src/glx/glxcmds.c | 1 +
 src/glx/glxext.c  | 4 ++--
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/glx/glxcmds.c b/src/glx/glxcmds.c
index e8485acd80..4db0228eab 100644
--- a/src/glx/glxcmds.c
+++ b/src/glx/glxcmds.c
@@ -937,6 +937,7 @@ init_fbconfig_for_chooser(struct glx_config * config,
    config->fbconfigID = (GLXFBConfigID) (GLX_DONT_CARE);
    config->swapMethod = GLX_DONT_CARE;
+   config->sRGBCapable = GLX_DONT_CARE;
 #define MATCH_DONT_CARE( param )        \
diff --git a/src/glx/glxext.c b/src/glx/glxext.c
index 5f23d3717a..ca3bf9d027 100644
--- a/src/glx/glxext.c
+++ b/src/glx/glxext.c
@@ -402,8 +402,6 @@ __glXInitializeVisualConfigFromTags(struct glx_config * config, int count,
-   config->sRGBCapable = GL_FALSE;
     ** Additional properties may be in a list at the end
     ** of the reply.  They are in pairs of property type
@@ -660,6 +658,8 @@ createConfigsFromProperties(Display * dpy, int nvisuals, int nprops,
+      /* Older X servers don't send this so we default it here. */
+      m->sRGBCapable = GL_FALSE;
        __glXInitializeVisualConfigFromTags(m, nprops, props,
                                           tagged_only, GL_TRUE);
       m->screen = screen;

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