From ba68d11840da0ea10b863c598b1947fa1090a557 Mon Sep 17 00:00:00 2001
From: Marius Ungureanu <maungu@microsoft.com>
Date: Wed, 2 Dec 2020 17:39:31 +0200
Subject: [PATCH] Optimize querying symbolic hotkeys

This API is not threadsafe and there is no alternative API for querying
whether the symbolic hotkeys have changed.

Instead, we can check the last modification time of the preferences file
and only update the symbolic hotkeys _iff_ the underlying storage file
has changed.
---
 gdk/quartz/gdkkeys-quartz.c | 40 +++++++++++++++++++++++++++++++++++--
 1 file changed, 38 insertions(+), 2 deletions(-)

diff --git a/gdk/quartz/gdkkeys-quartz.c b/gdk/quartz/gdkkeys-quartz.c
index 5a4d88787d..8ee8628dd2 100644
--- a/gdk/quartz/gdkkeys-quartz.c
+++ b/gdk/quartz/gdkkeys-quartz.c
@@ -58,6 +58,8 @@
 #include "gdkprivate-quartz.h"
 #include <Foundation/Foundation.h>
 
+#include <glib/gstdio.h>
+
 #define NUM_KEYCODES 128
 #define KEYVALS_PER_KEYCODE 4
 
@@ -68,6 +70,7 @@ static GdkKeymap *default_keymap = NULL;
  */
 static guint *keyval_array = NULL;
 static CFArrayRef global_hotkeys = NULL;
+static struct timespec preferences_last_mtime = {};
 
 static inline UniChar
 macroman2ucs (unsigned char c)
@@ -815,12 +818,45 @@ gdk_keymap_map_virtual_modifiers (GdkKeymap       *keymap,
   return TRUE;
 }
 
+static gboolean
+should_update_symbolic_hotkeys ()
+{
+  gchar *path_segments[] = {
+    g_get_home_dir(),
+    "Library",
+    "Preferences",
+    "com.apple.symbolichotkeys.plist",
+    NULL,
+  };
+
+  gchar *preferences_file = g_build_pathv(G_DIR_SEPARATOR_S, path_segments);
+  GStatBuf buf;
+
+  int res = g_stat(preferences_file, &buf);
+  g_free(preferences_file);
+
+  if (res != 0) {
+    /* In case we have any IO error, ensure correctness by querying */
+    return TRUE;
+  }
+
+  bool preferences_file_modified = preferences_last_mtime.tv_sec != buf.st_mtimespec.tv_sec
+    && preferences_last_mtime.tv_nsec != buf.st_mtimespec.tv_nsec;
+
+  preferences_last_mtime.tv_sec = buf.st_mtimespec.tv_sec;
+  preferences_last_mtime.tv_nsec = buf.st_mtimespec.tv_nsec;
+
+  return preferences_file_modified;
+}
+
 void
 _gdk_quartz_update_symbolic_hotkeys ()
 {
-  _gdk_quartz_release_symbolic_hotkeys ();
+  if (should_update_symbolic_hotkeys ()) {
+    _gdk_quartz_release_symbolic_hotkeys ();
 
-  CopySymbolicHotKeys (&global_hotkeys);
+    CopySymbolicHotKeys (&global_hotkeys);
+  }
 }
 
 void
-- 
2.21.1 (Apple Git-122.3)