[gtk+] wayland: Make sure window titles fit into a wl_buffer

[Timm Bäder <baedert src gnome org>]

commit d9a6517d5f9371648c625e75b3deb413f960c2f3
Author: Timm Bäder <mail baedert org>
Date:   Wed Jun 8 07:31:45 2016 +0200

    wayland: Make sure window titles fit into a wl_buffer
    
    A wl_buffer has a max size of 4096 bytes, of which 8 are needed for the
    header and another 4 for the string argument length (in this case), so
    make sure the we only save the first 4083 bytes that are still valid
    UTF8.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=767241

 gdk/wayland/gdkwindow-wayland.c |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)
---
diff --git a/gdk/wayland/gdkwindow-wayland.c b/gdk/wayland/gdkwindow-wayland.c
index f98ff59..d548458 100644
--- a/gdk/wayland/gdkwindow-wayland.c
+++ b/gdk/wayland/gdkwindow-wayland.c
@@ -61,6 +61,8 @@ static guint signals[LAST_SIGNAL];
    GDK_WINDOW_TYPE (window) != GDK_WINDOW_FOREIGN && \
    GDK_WINDOW_TYPE (window) != GDK_WINDOW_OFFSCREEN)
 
+#define MAX_WL_BUFFER_SIZE (4083) /* 4096 minus header, string argument length and NUL byte */
+
 typedef struct _GdkWaylandWindow GdkWaylandWindow;
 typedef struct _GdkWaylandWindowClass GdkWaylandWindowClass;
 
@@ -2267,6 +2269,7 @@ gdk_wayland_window_set_title (GdkWindow   *window,
                               const gchar *title)
 {
   GdkWindowImplWayland *impl;
+  const char *end;
   g_return_if_fail (title != NULL);
 
   if (GDK_WINDOW_DESTROYED (window))
@@ -2275,7 +2278,11 @@ gdk_wayland_window_set_title (GdkWindow   *window,
   impl = GDK_WINDOW_IMPL_WAYLAND (window->impl);
 
   g_free (impl->title);
-  impl->title = g_strdup (title);
+
+  g_utf8_validate (title, MAX_WL_BUFFER_SIZE, &end);
+  impl->title = g_malloc (end - title + 1);
+  memcpy (impl->title, title, end - title);
+  impl->title[end - title] = '\0';
 
   gdk_wayland_window_sync_title (window);
 }