[PATCH xserver 5/5] glamor: Use GL_RGBA format for 8-bit depth

[Olivier Fourdan]

For some hardware, GL_RGBA is the safest option for textures to bind to
an FBO for depth 8 as GL_ALPHA might be unsupported.

This allows using glamor-xv on hardware that don't support GL_ALPHA
textures attaching to an FBO, such as nouveau on nv30.

Newer hardware use GL_RED and texture swizzle anyway, so this change is
of limited impact.

Signed-off-by: Olivier Fourdan <ofourdan at redhat.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100710
---
 glamor/glamor.c       |  2 ++
 glamor/glamor_priv.h  |  1 +
 glamor/glamor_utils.h | 11 ++++++-----
 3 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/glamor/glamor.c b/glamor/glamor.c
index 2467443..f5fbed1 100644
--- a/glamor/glamor.c
+++ b/glamor/glamor.c
@@ -659,9 +659,11 @@ glamor_init(ScreenPtr screen, unsigned int flags)
          (glamor_priv->gl_flavor != GLAMOR_GL_DESKTOP && gl_version >= 30));
 
     glamor_priv->one_channel_format = GL_ALPHA;
+    glamor_priv->eight_bit_channel_format = GL_RGBA;
     if (epoxy_has_gl_extension("GL_ARB_texture_rg") &&
         glamor_priv->has_texture_swizzle) {
         glamor_priv->one_channel_format = GL_RED;
+        glamor_priv->eight_bit_channel_format = GL_RED;
     }
 
     glamor_set_debug_level(&glamor_debug_level);
diff --git a/glamor/glamor_priv.h b/glamor/glamor_priv.h
index 66a870f..28166ea 100644
--- a/glamor/glamor_priv.h
+++ b/glamor/glamor_priv.h
@@ -205,6 +205,7 @@ typedef struct glamor_screen_private {
     int max_fbo_size;
 
     GLuint one_channel_format;
+    GLuint eight_bit_channel_format;
 
     /* glamor point shader */
     glamor_program point_prog;
diff --git a/glamor/glamor_utils.h b/glamor/glamor_utils.h
index 6b88527..1b84499 100644
--- a/glamor/glamor_utils.h
+++ b/glamor/glamor_utils.h
@@ -620,12 +620,13 @@ gl_iformat_for_pixmap(PixmapPtr pixmap)
     glamor_screen_private *glamor_priv =
         glamor_get_screen_private((pixmap)->drawable.pScreen);
 
-    if (glamor_priv->gl_flavor == GLAMOR_GL_DESKTOP &&
-        ((pixmap)->drawable.depth == 1 || (pixmap)->drawable.depth == 8)) {
-        return glamor_priv->one_channel_format;
-    } else {
-        return GL_RGBA;
+    if (glamor_priv->gl_flavor == GLAMOR_GL_DESKTOP) {
+        if ((pixmap)->drawable.depth == 1)
+            return glamor_priv->one_channel_format;
+        if ((pixmap)->drawable.depth == 8)
+            return glamor_priv->eight_bit_channel_format;
     }
+    return GL_RGBA;
 }
 
 static inline CARD32
-- 
2.9.3