st/mesa: don't flush the front buffer if it's a pbuffer

This is the best guess I can make here.

Reviewed-by: Emil Velikov <[email protected]>

1 files changed, 13 insertions, 3 deletions

diff --git a/src/mesa/state_tracker/st_manager.c b/src/mesa/state_tracker/st_manager.c
index 5efbd1fa1d2..bee1f6b1366 100644
--- a/src/mesa/state_tracker/st_manager.c
+++ b/src/mesa/state_tracker/st_manager.c
@@ -1130,9 +1130,19 @@ st_manager_flush_frontbuffer(struct st_context *st)
    struct st_framebuffer *stfb = st_ws_framebuffer(st->ctx->DrawBuffer);
    struct st_renderbuffer *strb = NULL;
 
-   if (stfb)
-      strb = st_renderbuffer(stfb->Base.Attachment[BUFFER_FRONT_LEFT].
-                             Renderbuffer);
+   if (!stfb)
+      return;
+
+   /* If the context uses a doublebuffered visual, but the buffer is
+    * single-buffered, guess that it's a pbuffer, which doesn't need
+    * flushing.
+    */
+   if (st->ctx->Visual.doubleBufferMode &&
+       !stfb->Base.Visual.doubleBufferMode)
+      return;
+
+   strb = st_renderbuffer(stfb->Base.Attachment[BUFFER_FRONT_LEFT].
+                          Renderbuffer);
 
    /* Do we have a front color buffer and has it been drawn to since last
     * frontbuffer flush?