[gtk+/gtk-3-18] wayland: clean up stride calculation when creating shm surface

[Matthias Clasen <matthiasc src gnome org>]

commit 6c192a8856b8fff65dd86b4c6bda28c045e098f8
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 4f60573..b19b6a0 100644
--- a/gdk/wayland/gdkdisplay-wayland.c
+++ b/gdk/wayland/gdkdisplay-wayland.c
@@ -1056,7 +1056,7 @@ _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,
@@ -1067,11 +1067,11 @@ _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,