[metacity] compositor-xrender: do not create shadows when disabled

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 5645c166e9a44e55d98b819814dc6c13dfd97c89
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Mon Jul 13 20:19:00 2020 +0300

    compositor-xrender: do not create shadows when disabled
    
    https://gitlab.gnome.org/GNOME/metacity/-/issues/12

 src/compositor/meta-compositor-xrender.c |  6 ++++++
 src/compositor/meta-compositor-xrender.h |  2 ++
 src/compositor/meta-surface-xrender.c    | 12 +++++++-----
 3 files changed, 15 insertions(+), 5 deletions(-)
---
diff --git a/src/compositor/meta-compositor-xrender.c b/src/compositor/meta-compositor-xrender.c
index 64b8eaea..6acd3297 100644
--- a/src/compositor/meta-compositor-xrender.c
+++ b/src/compositor/meta-compositor-xrender.c
@@ -1192,6 +1192,12 @@ meta_compositor_xrender_new (MetaDisplay  *display,
                          NULL);
 }
 
+gboolean
+meta_compositor_xrender_have_shadows (MetaCompositorXRender *self)
+{
+  return self->have_shadows;
+}
+
 MetaShadowXRender *
 meta_compositor_xrender_create_shadow (MetaCompositorXRender *self,
                                        MetaSurface           *surface)
diff --git a/src/compositor/meta-compositor-xrender.h b/src/compositor/meta-compositor-xrender.h
index b419ee63..d07c47ec 100644
--- a/src/compositor/meta-compositor-xrender.h
+++ b/src/compositor/meta-compositor-xrender.h
@@ -31,6 +31,8 @@ G_DECLARE_FINAL_TYPE (MetaCompositorXRender, meta_compositor_xrender,
 MetaCompositor    *meta_compositor_xrender_new           (MetaDisplay            *display,
                                                           GError                **error);
 
+gboolean           meta_compositor_xrender_have_shadows  (MetaCompositorXRender  *self);
+
 MetaShadowXRender *meta_compositor_xrender_create_shadow (MetaCompositorXRender  *self,
                                                           MetaSurface            *surface);
 
diff --git a/src/compositor/meta-surface-xrender.c b/src/compositor/meta-surface-xrender.c
index f8a03e8a..1ce839fe 100644
--- a/src/compositor/meta-surface-xrender.c
+++ b/src/compositor/meta-surface-xrender.c
@@ -497,16 +497,18 @@ meta_surface_xrender_pre_paint (MetaSurface   *surface,
 
   if (self->shadow_changed)
     {
+      MetaCompositor *compositor;
+      MetaCompositorXRender *compositor_xrender;
+
+      compositor = meta_surface_get_compositor (surface);
+      compositor_xrender = META_COMPOSITOR_XRENDER (compositor);
+
       if (self->shadow == NULL &&
+          meta_compositor_xrender_have_shadows (compositor_xrender) &&
           meta_surface_has_shadow (surface))
         {
-          MetaCompositor *compositor;
-          MetaCompositorXRender *compositor_xrender;
           XserverRegion shadow_region;
 
-          compositor = meta_surface_get_compositor (surface);
-          compositor_xrender = META_COMPOSITOR_XRENDER (compositor);
-
           self->shadow = meta_compositor_xrender_create_shadow (compositor_xrender,
                                                                 surface);