gallium: more elaborate tracking of front color buffer state

This fixes the case where the app calls SwapBuffers then calls glReadPixels
to read the front color buffer.  We now keep track of when the front buffer
is a _logically_ copy of the back buffer (after SwapBuffers) and read from
the back color buffer instead of the front.

1 files changed, 6 insertions, 3 deletions

diff --git a/src/mesa/state_tracker/st_context.h b/src/mesa/state_tracker/st_context.h
index 212687cf4a..d89e54c43c 100644
--- a/src/mesa/state_tracker/st_context.h
+++ b/src/mesa/state_tracker/st_context.h
@@ -45,6 +45,11 @@ struct blit_state;
 struct bitmap_cache;
 
 
+#define FRONT_STATUS_UNDEFINED    0
+#define FRONT_STATUS_DIRTY        1
+#define FRONT_STATUS_COPY_OF_BACK 2
+
+
 #define ST_NEW_MESA                    0x1 /* Mesa state has changed */
 #define ST_NEW_FRAGMENT_PROGRAM        0x2
 #define ST_NEW_VERTEX_PROGRAM          0x4
@@ -104,9 +109,7 @@ struct st_context
       struct gl_fragment_program *fragment_program;
    } cb;
 
-   struct {
-      GLuint frontbuffer_dirty:1;
-   } flags;
+   GLuint frontbuffer_status;  /**< one of FRONT_STATUS_ */
 
    char vendor[100];
    char renderer[100];