[gtk+] wayland: clean up stride calculation when creating shm surface

[Ray Strode <halfline src gnome org>]

commit 1e001eaa7874bc00cfc3a2c86e8e40b0fe18c4e5
Author: Ray Strode <rstrode redhat com>
Date:   Wed Jan 20 11:40:34 2016 -0500

    wayland: clean up stride calculation when creating shm surface
    
    Right now, we assume the stride for the image surface needs to
    be 4 byte aligned.  This is, in fact, true, but it's better to
    ask cairo for the alignment requirement directly rather than
    assume we know the alignment rules.
    
    This commit changes the code to use cairo_format_stride_for_width
    to calculate a suitable rowstride for pixman.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=760897

 gdk/wayland/gdkdisplay-wayland.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/gdk/wayland/gdkdisplay-wayland.c b/gdk/wayland/gdkdisplay-wayland.c
index 2f0c64e..bf3c20c 100644
--- a/gdk/wayland/gdkdisplay-wayland.c
+++ b/gdk/wayland/gdkdisplay-wayland.c
@@ -1005,7 +1005,7 @@ _gdk_wayland_display_create_shm_surface (GdkWaylandDisplay *display,
   data->scale = scale;
   data->busy = FALSE;
 
-  stride = width * 4;
+  stride = cairo_format_stride_for_width (CAIRO_FORMAT_ARGB32, width*scale);
 
   data->pool = create_shm_pool (display->shm,
                                 width*scale, height*scale,
@@ -1016,11 +1016,11 @@ _gdk_wayland_display_create_shm_surface (GdkWaylandDisplay *display,
                                                  CAIRO_FORMAT_ARGB32,
                                                  width*scale,
                                                  height*scale,
-                                                 stride*scale);
+                                                 stride);
 
   data->buffer = wl_shm_pool_create_buffer (data->pool, 0,
                                             width*scale, height*scale,
-                                            stride*scale, WL_SHM_FORMAT_ARGB8888);
+                                            stride, WL_SHM_FORMAT_ARGB8888);
   wl_buffer_add_listener (data->buffer, &buffer_listener, surface);
 
   cairo_surface_set_user_data (surface, &gdk_wayland_cairo_key,