app: move GimpDisplayShell pointer/keyboard grabbing to utility functions

Spit warnings in the functions if grabbing fails and return a boolean
success value. Bail out in the callers upon grab failure instead of
assuming that grabbing always succeeds and running into an
inconsistent state that can cause all sorts of problems.

app/display/gimpdisplayshell-grab.c

@@ -0,0 +1,109 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpdisplayshell-grab.c
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include <gtk/gtk.h>
+
+#include "display-types.h"
+
+#include "gimpdisplayshell.h"
+#include "gimpdisplayshell-grab.h"
+
+
+gboolean
+gimp_display_shell_pointer_grab (GimpDisplayShell *shell,
+                                 GdkEvent         *event,
+                                 GdkEventMask      event_mask)
+{
+  GdkGrabStatus status;
+
+  g_return_val_if_fail (GIMP_IS_DISPLAY_SHELL (shell), FALSE);
+  g_return_val_if_fail (event != NULL, FALSE);
+  g_return_val_if_fail (shell->pointer_grabbed == FALSE, FALSE);
+
+  status = gdk_pointer_grab (gtk_widget_get_window (shell->canvas),
+                             FALSE, event_mask, NULL, NULL,
+                             gdk_event_get_time (event));
+
+  if (status == GDK_GRAB_SUCCESS)
+    {
+      shell->pointer_grabbed = TRUE;
+
+      return TRUE;
+    }
+
+  g_printerr ("%s: gdk_pointer_grab failed with status %d\n",
+              G_STRFUNC, status);
+
+  return FALSE;
+}
+
+void
+gimp_display_shell_pointer_ungrab (GimpDisplayShell *shell,
+                                   GdkEvent         *event)
+{
+  g_return_if_fail (shell->pointer_grabbed == TRUE);
+
+  gdk_display_pointer_ungrab (gtk_widget_get_display (shell->canvas),
+                              gdk_event_get_time (event));
+
+  shell->pointer_grabbed = FALSE;
+}
+
+gboolean
+gimp_display_shell_keyboard_grab (GimpDisplayShell *shell,
+                                  GdkEvent         *event)
+{
+  GdkGrabStatus status;
+
+  g_return_val_if_fail (GIMP_IS_DISPLAY_SHELL (shell), FALSE);
+  g_return_val_if_fail (event != NULL, FALSE);
+  g_return_val_if_fail (shell->keyboard_grabbed == FALSE, FALSE);
+
+  status = gdk_keyboard_grab (gtk_widget_get_window (shell->canvas),
+                              FALSE,
+                              gdk_event_get_time (event));
+
+  if (status == GDK_GRAB_SUCCESS)
+    {
+      shell->keyboard_grabbed = TRUE;
+
+      return TRUE;
+    }
+
+  g_printerr ("%s: gdk_keyboard_grab failed with status %d\n",
+              G_STRFUNC, status);
+
+  return FALSE;
+}
+
+void
+gimp_display_shell_keyboard_ungrab (GimpDisplayShell *shell,
+                                    GdkEvent         *event)
+{
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (event != NULL);
+  g_return_if_fail (shell->keyboard_grabbed == TRUE);
+
+  gdk_display_keyboard_ungrab (gtk_widget_get_display (shell->canvas),
+                               gdk_event_get_time (event));
+
+  shell->keyboard_grabbed = FALSE;
+}