[Mesa-dev] [PATCH 2/2] intel/pixel_read: Properly flip the results for window system buffers

[Jason Ekstrand]

https://bugs.freedesktop.org/show_bug.cgi?id=88841
---
 src/mesa/drivers/dri/i965/intel_pixel_read.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/src/mesa/drivers/dri/i965/intel_pixel_read.c b/src/mesa/drivers/dri/i965/intel_pixel_read.c
index babf8ca..198d616 100644
--- a/src/mesa/drivers/dri/i965/intel_pixel_read.c
+++ b/src/mesa/drivers/dri/i965/intel_pixel_read.c
@@ -155,6 +155,17 @@ intel_readpixels_tiled_memcpy(struct gl_context * ctx,
 
    dst_pitch = _mesa_image_row_stride(pack, width, format, type);
 
+   /* For a window-system renderbuffer, the buffer is actually flipped
+    * vertically, so we need to handle that.  Because we don't want to
+    * mess up the detiling, we mangle the height and pixels pointer and
+    * give the detiling function a negative pitch.
+    */
+   if (rb->Name == 0) {
+      yoffset = rb->Height - yoffset - height;
+      pixels += (ptrdiff_t) (height - 1) * dst_pitch;
+      dst_pitch = -dst_pitch;
+   }
+
    /* We postponed printing this message until having committed to executing
     * the function.
     */
-- 
2.2.2