Implement monitor change functions on GNUstep

* src/nsfns.m (Fns_display_monitor_attributes_list): Fix coding
style.
* src/nsterm.m (nstrace_leave, nstrace_restore_global_trace_state)
(nstrace_fullscreen_type_name): Fix coding style.
(ns_displays_reconfigured, ns_term_init): Make a record of the
previous display attributes list and avoid storing duplicate
events.
([EmacsApp init]): Listen for
NSApplicationDidChangeScreenParametersNotification.
([EmacsApp updateMonitors:]): New method.
(syms_of_nsterm): New staticpro.

2 files changed, 95 insertions, 28 deletions

diff --git a/src/nsfns.m b/src/nsfns.m
index 818ba6f40f1..20c36209eb5 100644
--- a/src/nsfns.m
+++ b/src/nsfns.m
@@ -2769,7 +2769,8 @@ Internal use only, use `display-monitor-attributes-list' instead.  */)
         }
       else
         {
-          // Flip y coordinate as NS has y starting from the bottom.
+          /* Flip y coordinate as NS screen coordinates originate from
+             the bottom.  */
           y = (short) (primary_display_height - fr.size.height - fr.origin.y);
           vy = (short) (primary_display_height -
                         vfr.size.height - vfr.origin.y);
@@ -2781,11 +2782,12 @@ Internal use only, use `display-monitor-attributes-list' instead.  */)
       m->geom.height = (unsigned short) fr.size.height;
 
       m->work.x = (short) vfr.origin.x;
-      // y is flipped on NS, so vy - y are pixels missing at the bottom,
-      // and fr.size.height - vfr.size.height are pixels missing in total.
-      // Pixels missing at top are
-      // fr.size.height - vfr.size.height - vy + y.
-      // work.y is then pixels missing at top + y.
+      /* y is flipped on NS, so vy - y are pixels missing at the
+         bottom, and fr.size.height - vfr.size.height are pixels
+         missing in total.
+
+         Pixels missing at top are fr.size.height - vfr.size.height -
+         vy + y.  work.y is then pixels missing at top + y.  */
       m->work.y = (short) (fr.size.height - vfr.size.height) - vy + y + y;
       m->work.width = (unsigned short) vfr.size.width;
       m->work.height = (unsigned short) vfr.size.height;
@@ -2800,13 +2802,14 @@ Internal use only, use `display-monitor-attributes-list' instead.  */)
       }
 
 #else
-      // Assume 92 dpi as x-display-mm-height/x-display-mm-width does.
+      /* Assume 92 dpi as x-display-mm-height and x-display-mm-width
+         do.  */
       m->mm_width = (int) (25.4 * fr.size.width / 92.0);
       m->mm_height = (int) (25.4 * fr.size.height / 92.0);
 #endif
     }
 
-  // Primary monitor is always first for NS.
+  /* Primary monitor is always ordered first for NS.  */
   attributes_list = ns_make_monitor_attribute_list (monitors, n_monitors,
                                                     0, "NS");
 
diff --git a/src/nsterm.m b/src/nsterm.m
index 67b02c7a54a..d7e62a70c49 100644
--- a/src/nsterm.m
+++ b/src/nsterm.m
@@ -79,6 +79,9 @@ static EmacsMenu *dockMenu;
 static EmacsMenu *mainMenu;
 #endif
 
+/* The last known monitor attributes list.  */
+static Lisp_Object last_known_monitors;
+
 /* ==========================================================================
 
    NSTRACE, Trace support.
@@ -89,8 +92,8 @@ static EmacsMenu *mainMenu;
 
 /* The following use "volatile" since they can be accessed from
    parallel threads.  */
-volatile int nstrace_num = 0;
-volatile int nstrace_depth = 0;
+volatile int nstrace_num;
+volatile int nstrace_depth;
 
 /* When 0, no trace is emitted.  This is used by NSTRACE_WHEN and
    NSTRACE_UNLESS to silence functions called.
@@ -101,33 +104,41 @@ volatile int nstrace_depth = 0;
 volatile int nstrace_enabled_global = 1;
 
 /* Called when nstrace_enabled goes out of scope.  */
-void nstrace_leave(int * pointer_to_nstrace_enabled)
+void
+nstrace_leave (int *pointer_to_nstrace_enabled)
 {
   if (*pointer_to_nstrace_enabled)
-    {
-      --nstrace_depth;
-    }
+    --nstrace_depth;
 }
 
 
 /* Called when nstrace_saved_enabled_global goes out of scope.  */
-void nstrace_restore_global_trace_state(int * pointer_to_saved_enabled_global)
+void
+nstrace_restore_global_trace_state (int *pointer_to_saved_enabled_global)
 {
   nstrace_enabled_global = *pointer_to_saved_enabled_global;
 }
 
 
-char const * nstrace_fullscreen_type_name (int fs_type)
+const char *
+nstrace_fullscreen_type_name (int fs_type)
 {
   switch (fs_type)
     {
-    case -1:                   return "-1";
-    case FULLSCREEN_NONE:      return "FULLSCREEN_NONE";
-    case FULLSCREEN_WIDTH:     return "FULLSCREEN_WIDTH";
-    case FULLSCREEN_HEIGHT:    return "FULLSCREEN_HEIGHT";
-    case FULLSCREEN_BOTH:      return "FULLSCREEN_BOTH";
-    case FULLSCREEN_MAXIMIZED: return "FULLSCREEN_MAXIMIZED";
-    default:                   return "FULLSCREEN_?????";
+    case -1:
+      return "-1";
+    case FULLSCREEN_NONE:
+      return "FULLSCREEN_NONE";
+    case FULLSCREEN_WIDTH:
+      return "FULLSCREEN_WIDTH";
+    case FULLSCREEN_HEIGHT:
+      return "FULLSCREEN_HEIGHT";
+    case FULLSCREEN_BOTH:
+      return "FULLSCREEN_BOTH";
+    case FULLSCREEN_MAXIMIZED:
+      return "FULLSCREEN_MAXIMIZED";
+    default:
+      return "FULLSCREEN_?????";
     }
 }
 #endif
@@ -5221,9 +5232,17 @@ ns_displays_reconfigured (CGDirectDisplayID display,
 {
   struct input_event ie;
   union buffered_input_event *ev;
+  Lisp_Object new_monitors;
 
   EVENT_INIT (ie);
 
+  new_monitors = Fns_display_monitor_attributes_list (Qnil);
+
+  if (!NILP (Fequal (new_monitors, last_known_monitors)))
+    return;
+
+  last_known_monitors = new_monitors;
+
   ev = (kbd_store_ptr == kbd_buffer
         ? kbd_buffer + KBD_BUFFER_SIZE - 1
         : kbd_store_ptr - 1);
@@ -5601,6 +5620,7 @@ ns_term_init (Lisp_Object display_name)
   CGDisplayRegisterReconfigurationCallback (ns_displays_reconfigured,
                                             NULL);
 #endif
+  last_known_monitors = Fns_display_monitor_attributes_list (Qnil);
 
   NSTRACE_MSG ("ns_term_init done");
 
@@ -5642,6 +5662,10 @@ ns_term_shutdown (int sig)
 
 - (id)init
 {
+#ifdef NS_IMPL_GNUSTEP
+  NSNotificationCenter *notification_center;
+#endif
+
   NSTRACE ("[EmacsApp init]");
 
   if ((self = [super init]))
@@ -5654,6 +5678,14 @@ ns_term_shutdown (int sig)
 #endif
     }
 
+#ifdef NS_IMPL_GNUSTEP
+  notification_center = [NSNotificationCenter defaultCenter];
+  [notification_center addObserver: self
+                          selector: @selector(updateMonitors:)
+                              name: NSApplicationDidChangeScreenParametersNotification
+                            object: nil];
+#endif
+
   return self;
 }
 
@@ -5666,11 +5698,11 @@ ns_term_shutdown (int sig)
 #define NSAppKitVersionNumber10_9 1265
 #endif
 
-    if ((int)NSAppKitVersionNumber != NSAppKitVersionNumber10_9)
-      {
-        [super run];
-        return;
-      }
+  if ((int) NSAppKitVersionNumber != NSAppKitVersionNumber10_9)
+    {
+      [super run];
+      return;
+    }
 
   NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
 
@@ -5854,6 +5886,36 @@ ns_term_shutdown (int sig)
   return YES;
 }
 
+#ifdef NS_IMPL_GNUSTEP
+- (void) updateMonitors: (NSNotification *) notification
+{
+  struct input_event ie;
+  union buffered_input_event *ev;
+  Lisp_Object new_monitors;
+
+  EVENT_INIT (ie);
+
+  new_monitors = Fns_display_monitor_attributes_list (Qnil);
+
+  if (!NILP (Fequal (new_monitors, last_known_monitors)))
+    return;
+
+  last_known_monitors = new_monitors;
+
+  ev = (kbd_store_ptr == kbd_buffer
+        ? kbd_buffer + KBD_BUFFER_SIZE - 1
+        : kbd_store_ptr - 1);
+
+  if (kbd_store_ptr != kbd_fetch_ptr
+      && ev->ie.kind == MONITORS_CHANGED_EVENT)
+    return;
+
+  ie.kind = MONITORS_CHANGED_EVENT;
+  XSETTERMINAL (ie.arg, x_display_list->terminal);
+
+  kbd_buffer_store_event (&ie);
+}
+#endif
 
 /* **************************************************************************
 
@@ -10575,4 +10637,6 @@ This variable is ignored on macOS < 10.7 and GNUstep.  Default is t.  */);
   syms_of_nsfont ();
 #endif
 
+  last_known_monitors = Qnil;
+  staticpro (&last_known_monitors);
 }