Improve Kempston mouse handling under GTK+ 3.x.

On X11, warp relative to the top-level window (improves things on Phil's
laptop). On Wayland, don't warp at all as it causes a crash.

ChangeLog

@@ -1,12 +1,18 @@
 2018-09-??  Philip Kendall  <[email protected]>
 
+        * UI improvements:
+          * GTK+ 3: Make the offset entry wider in memory browser (Derek
+            Fountain).
+          * Improve Fuse's window sizing under Wayland; still not right, but
+            better than it was before (Sergio Baldoví).
+          * Improve Fuse's Kempston mouse handling under GTK+ 3.x (Philip
+            Kendall).
+          * Stop Kempston mouse causing a crash under Wayland; still doesn't
+            work properly though (Philip Kendall).
+
         * Miscellaneous improvements:
           * "Save binary" command can now save 65536 bytes again (regression
             introduced in 1.5.6; thanks, thrice) (Philip Kendall).
-          * GTK+ 3 UI: Make the offset entry wider in memory browser (Derek
-            Fountain).
-          * Improve Fuse's behaviour under Wayland; still not right, but
-            better than it was before (Sergio Baldoví).
           * Remove gcc 8 string overflow warnings (Philip Kendall).
 
 2018-08-06  Philip Kendall  <[email protected]>

ui/gtk/gtkmouse.c

@@ -30,6 +30,10 @@
 #include "gtkinternals.h"
 #include "ui/ui.h"
 
+#ifdef GDK_WINDOWING_WAYLAND
+#include <gdk/gdkwayland.h>
+#endif
+
 /* For XWarpPointer *only* - see below */
 #include <gdk/gdkx.h>
 #include <X11/Xlib.h>
@@ -46,8 +50,33 @@ gtkmouse_reset_pointer( void )
    * For Win32, use SetCursorPos() -- see sdpGtkWarpPointer() at
    * http://k3d.cvs.sourceforge.net/k3d/projects/sdplibs/sdpgtk/sdpgtkutility.cpp?view=markup
    */
-  GdkWindow *window = gtk_widget_get_window( gtkui_drawing_area );
+  GtkWindow *gtkwindow;
+  GdkWindow *window;
+
+  /* The logic here is a bit hairy:
+
+     * On GTK+ 2.x, we warp relative to the drawing area
+     * On GTK+ 3.x on X11, we warp relative to the top-level window
+     * On GTK+ 3.x on Wayland, we don't warp at all because it causes a
+       segfault (see bug #435)
+   */
+
+#if GTK_CHECK_VERSION( 3, 0, 0 )
+
+#ifdef GDK_WINDOWING_WAYLAND
+  GdkDisplay *display = gdk_display_get_default();
+  if( GDK_IS_WAYLAND_DISPLAY( display ) ) return;
+#endif                /* #ifdef GDK_WINDOWING_WAYLAND */
+
+  gtkwindow = gtkui_window;
+
+#else                 /* #if GTK_CHECK_VERSION( 3, 0, 0 ) */
+
+  gtkwindow = gtkui_drawing_area;
+
+#endif                /* #if GTK_CHECK_VERSION( 3, 0, 0 ) */
 
+  window = gtk_widget_get_window( gtkwindow );
   XWarpPointer( GDK_WINDOW_XDISPLAY( window ), None, 
                 GDK_WINDOW_XID( window ), 0, 0, 0, 0, 128, 128 );
 }