libgimpwidgets: New API to check system animation status

Ports the animation code started in e13cc635
to an independent gimp_widget_animation_enabled()
function. This allows plug-in authors to
also conditionally turn off animations if
the user's system settings say to do so.

The function is applied to the About
Dialogue animation as well as two Easter
Egg animations:
* Wilber's eyes blinking after 23 minutes
on an empty canvas
* Wilber's eyes following the mouse after
a certain sequence of tools is clicked

libgimpwidgets/gimpwidgetsutils.c

@@ -46,6 +46,9 @@
 #include <ApplicationServices/ApplicationServices.h>
 #include <CoreServices/CoreServices.h>
 #endif
+#ifdef PLATFORM_OSX
+#import <Cocoa/Cocoa.h>
+#endif
 
 #include "libgimpcolor/gimpcolor.h"
 #include "libgimpconfig/gimpconfig.h"
@@ -1159,6 +1162,43 @@ gimp_widget_set_native_handle (GtkWidget  *widget,
     gimp_widget_set_handle_on_mapped (widget, NULL, handle);
 }
 
+/**
+ * gimp_widget_animation_enabled:
+ *
+ * This function attempts to read the user's system preference for
+ * showing animation. It can be used to turn off or hide unnecessary
+ * animations such as the scrolling credits or Easter Egg animations.
+ *
+ * Returns: %TRUE if the user has animations enabled on their system
+ *
+ * Since: 3.0
+ */
+gboolean
+gimp_widget_animation_enabled (void)
+{
+  gboolean animation_enabled = TRUE;
+
+  /* Per Luca Bacci, KDE syncs their animation setting with GTK. See
+   * https://invent.kde.org/plasma/kde-gtk-config/-/blob/v6.0.90/kded/gtkconfig.cpp?ref_type=tags#L232
+   */
+  g_object_get (gtk_settings_get_default (),
+                "gtk-enable-animations", &animation_enabled,
+                NULL);
+
+#ifdef PLATFORM_OSX
+  /* The MacOS setting is TRUE if the user wants animations turned off, so
+   * we invert it to match the format of the other platforms */
+  animation_enabled =
+    ! ([[NSWorkspace sharedWorkspace] accessibilityDisplayShouldReduceMotion]);
+#endif
+#ifdef G_OS_WIN32
+  SystemParametersInfo (SPI_GETCLIENTAREAANIMATION, 0x00, &animation_enabled,
+                        0x00);
+#endif
+
+  return animation_enabled;
+}
+
 
 /* Internal functions */