st/mesa: use DXT SRGB formats for COMPRESSED_SRGB

And also check if the formats are supported to return something meaningful
if compression cannot be used.

diff --git a/src/mesa/state_tracker/st_format.c b/src/mesa/state_tracker/st_format.c
index 955d821..531fa94 100644 (file)
--- a/src/mesa/state_tracker/st_format.c
+++ b/src/mesa/state_tracker/st_format.c
@@ -717,18 +717,30 @@ st_choose_format(struct pipe_screen *screen, GLenum internalFormat,
 
    case GL_SRGB_EXT:
    case GL_SRGB8_EXT:
-   case GL_COMPRESSED_SRGB_EXT:
-   case GL_COMPRESSED_SRGB_ALPHA_EXT:
    case GL_SRGB_ALPHA_EXT:
    case GL_SRGB8_ALPHA8_EXT:
       return default_srgba_format( screen, target, sample_count, bindings,
                                    geom_flags );
+
+   case GL_COMPRESSED_SRGB_EXT:
    case GL_COMPRESSED_SRGB_S3TC_DXT1_EXT:
-      return PIPE_FORMAT_DXT1_SRGB;
+      if (screen->is_format_supported(screen, PIPE_FORMAT_DXT1_SRGB, target,
+                                      sample_count, bindings, geom_flags))
+         return PIPE_FORMAT_DXT1_SRGB;
+      return default_srgba_format( screen, target, sample_count, bindings,
+                                   geom_flags );
+
    case GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT1_EXT:
       return PIPE_FORMAT_DXT1_SRGBA;
+
+   case GL_COMPRESSED_SRGB_ALPHA_EXT:
    case GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT3_EXT:
-      return PIPE_FORMAT_DXT3_SRGBA;
+      if (screen->is_format_supported(screen, PIPE_FORMAT_DXT3_SRGBA, target,
+                                      sample_count, bindings, geom_flags))
+         return PIPE_FORMAT_DXT3_SRGBA;
+      return default_srgba_format( screen, target, sample_count, bindings,
+                                   geom_flags );
+
    case GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT:
       return PIPE_FORMAT_DXT5_SRGBA;