[mutter/wip/another-16bpp-crasher: 2/2] iconcache: Avoid xrender picture formats when creating cairo surface

[Ray Strode <halfline src gnome org>]

commit 0768014e06e0d538f3126a8cd5e4d27ee2d1a83e
Author: Ray Strode <rstrode redhat com>
Date:   Mon Aug 5 14:39:21 2019 -0400

    iconcache: Avoid xrender picture formats when creating cairo surface
    
    If an application provides its window icon via wmhints, then mutter
    loads the pixmap specified by the application into a cairo xlib surface. When
    creating the surface it specifies the visual, indirectly, via an XRender
    picture format.
    
    This is suboptimal, since XRender picture formats don't have a way to specify
    16bpp depth, which an application may be using.
    
    In particular, applications are likely to use 16bpp depth pixmaps for their
    icons, if the video card offers a 16bpp framebuffer/root window.
    
    This commit drops the XRender middleman, and just tells cairo a visual to use
    directly.

 src/x11/iconcache.c | 31 ++++++-------------------------
 1 file changed, 6 insertions(+), 25 deletions(-)
---
diff --git a/src/x11/iconcache.c b/src/x11/iconcache.c
index 15d72da65..521c77b8d 100644
--- a/src/x11/iconcache.c
+++ b/src/x11/iconcache.c
@@ -288,34 +288,12 @@ get_pixmap_geometry (MetaX11Display *x11_display,
     *d = depth;
 }
 
-static int
-standard_pict_format_for_depth (int depth)
-{
-  switch (depth)
-    {
-    case 1:
-      return PictStandardA1;
-    case 24:
-      return PictStandardRGB24;
-    case 32:
-      return PictStandardARGB32;
-    default:
-      g_assert_not_reached ();
-    }
-  return 0;
-}
-
-static XRenderPictFormat *
-pict_format_for_depth (Display *xdisplay, int depth)
-{
-  return XRenderFindStandardFormat (xdisplay, standard_pict_format_for_depth (depth));
-}
-
 static cairo_surface_t *
 surface_from_pixmap (Display *xdisplay, Pixmap xpixmap,
                      int width, int height)
 {
   Window root_return;
+  XVisualInfo visual_info;
   int x_ret, y_ret;
   unsigned int w_ret, h_ret, bw_ret, depth_ret;
 
@@ -323,8 +301,11 @@ surface_from_pixmap (Display *xdisplay, Pixmap xpixmap,
                      &x_ret, &y_ret, &w_ret, &h_ret, &bw_ret, &depth_ret))
     return NULL;
 
-  return cairo_xlib_surface_create_with_xrender_format (xdisplay, xpixmap, DefaultScreenOfDisplay (xdisplay),
-                                                        pict_format_for_depth (xdisplay, depth_ret), w_ret, 
h_ret);
+  if (!XMatchVisualInfo (xdisplay, DefaultScreen (xdisplay),
+                         depth_ret, TrueColor, &visual_info))
+    return NULL;
+
+  return cairo_xlib_surface_create (xdisplay, xpixmap, visual_info.visual, w_ret, h_ret);
 }
 
 static gboolean