intel: Don't mark front buffer dirty if we're only reading

When we call intel_prepare_render() from intelReadPixels(), we'll mark
the front buffer dirty.  That's silly, since we're only reading from it
and marking it dirty will cause us to copy from fake front to front
eventually.

Just clear the dirty flag after doing the read.

1 files changed, 12 insertions, 1 deletions

diff --git a/src/mesa/drivers/dri/intel/intel_pixel_read.c b/src/mesa/drivers/dri/intel/intel_pixel_read.c
index 2ac3da7f42..0c95a975ff 100644
--- a/src/mesa/drivers/dri/intel/intel_pixel_read.c
+++ b/src/mesa/drivers/dri/intel/intel_pixel_read.c
@@ -170,11 +170,19 @@ intelReadPixels(GLcontext * ctx,
                 GLenum format, GLenum type,
                 const struct gl_pixelstore_attrib *pack, GLvoid * pixels)
 {
+   struct intel_context *intel = intel_context(ctx);
+   GLboolean dirty;
+
    if (INTEL_DEBUG & DEBUG_PIXEL)
       fprintf(stderr, "%s\n", __FUNCTION__);
 
    intelFlush(ctx);
-   intel_prepare_render(intel_context(ctx));
+
+   /* glReadPixels() wont dirty the front buffer, so reset the dirty
+    * flag after calling intel_prepare_render(). */
+   dirty = intel->front_buffer_dirty;
+   intel_prepare_render(intel);
+   intel->front_buffer_dirty = dirty;
 
    if (do_blit_readpixels
        (ctx, x, y, width, height, format, type, pack, pixels))
@@ -193,4 +201,7 @@ intelReadPixels(GLcontext * ctx,
       _mesa_update_state(ctx);
 
    _swrast_ReadPixels(ctx, x, y, width, height, format, type, pack, pixels);
+
+   /* There's an intel_prepare_render() call in intelSpanRenderStart(). */
+   intel->front_buffer_dirty = dirty;
 }