quartz: Add monitor support

This is a backport of a patch by Tom Schoonjans,

https://bugzilla.gnome.org/show_bug.cgi?id=779184

gdk/quartz/gdkmonitor-quartz.c

@@ -0,0 +1,58 @@
+/*
+ * Copyright © 2017 Tom Schoonjans
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include <glib.h>
+#include <gio/gio.h>
+
+#include "gdkmonitor-quartz.h"
+#include "gdkscreen-quartz.h"
+
+
+G_DEFINE_TYPE (GdkQuartzMonitor, gdk_quartz_monitor, GDK_TYPE_MONITOR)
+
+static void
+gdk_quartz_monitor_get_workarea (GdkMonitor   *monitor,
+                                 GdkRectangle *dest)
+{
+  GdkQuartzScreen *quartz_screen = GDK_QUARTZ_SCREEN(gdk_display_get_default_screen (monitor->display));
+  GdkQuartzMonitor *quartz_monitor = GDK_QUARTZ_MONITOR(monitor);
+
+  GDK_QUARTZ_ALLOC_POOL;
+
+  NSRect rect = [quartz_monitor->nsscreen visibleFrame];
+
+  dest->x = rect.origin.x - quartz_screen->min_x;
+  dest->y = quartz_screen->height - (rect.origin.y + rect.size.height) + quartz_screen->min_y;
+  dest->width = rect.size.width;
+  dest->height = rect.size.height;
+
+  GDK_QUARTZ_RELEASE_POOL;
+}
+
+static void
+gdk_quartz_monitor_init (GdkQuartzMonitor *monitor)
+{
+}
+
+static void
+gdk_quartz_monitor_class_init (GdkQuartzMonitorClass *class)
+{
+  GDK_MONITOR_CLASS (class)->get_workarea = gdk_quartz_monitor_get_workarea;
+}
+