From 9519ebe96344ec64e8f18eae2420df101c446a1a Mon Sep 17 00:00:00 2001
From: Olivier Fourdan <ofourdan@redhat.com>
Date: Fri, 30 Apr 2021 16:23:10 +0200
Subject: [PATCH xserver 20/27] xwayland/eglstream: Set ALU to GXCopy for
 blitting
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The EGLstream backend's post damage function uses a shader and
glDrawArrays() to copy the data from the glamor's pixmap texture prior
to do the eglSwapBuffers().

However, glDrawArrays() can be affected by the GL state, and therefore
not reliably produce the expected copy, causing the content of the
buffer to be corrupted.

Make sure to set the ALU to GXCopy prior to call glDrawArrays() to get
the expected result.

Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Suggested-by: Michel Dänzer <mdaenzer@redhat.com>
(cherry picked from commit 012350e3db47fef0404346f55968032e62004fcf)
---
 hw/xwayland/xwayland-glamor-eglstream.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/hw/xwayland/xwayland-glamor-eglstream.c b/hw/xwayland/xwayland-glamor-eglstream.c
index 64f4e31f5..2094d293a 100644
--- a/hw/xwayland/xwayland-glamor-eglstream.c
+++ b/hw/xwayland/xwayland-glamor-eglstream.c
@@ -33,6 +33,7 @@
 #define EGL_NO_X11
 #include <glamor_egl.h>
 #include <glamor.h>
+#include <glamor_priv.h>
 #include <glamor_transform.h>
 #include <glamor_transfer.h>
 
@@ -727,6 +728,8 @@ xwl_glamor_eglstream_post_damage(struct xwl_window *xwl_window,
      * won't actually draw to it
      */
     xwl_glamor_egl_make_current(xwl_screen);
+    glamor_set_alu(xwl_screen->screen, GXcopy);
+
     glBindFramebuffer(GL_FRAMEBUFFER, 0);
 
     if (eglGetCurrentSurface(EGL_READ) != xwl_pixmap->surface ||
-- 
2.31.1