Store the old window size on OSX when toggling fullscreen windows.

On other systems the WM handles this, but on OSX for some reason you need to do this yourself?

src/macosx/osxgl.h

@@ -40,6 +40,9 @@ typedef struct ALLEGRO_DISPLAY_OSX_WIN {
    ALLEGRO_MUTEX *flip_mutex;
    ALLEGRO_COND *flip_cond;
    int num_flips;
+   /* These two store the old window size when restoring from a FS window. */
+   int old_w;
+   int old_h;
 } ALLEGRO_DISPLAY_OSX_WIN;
 
 /* This is our version of ALLEGRO_MOUSE_CURSOR */

src/macosx/osxgl.m

@@ -543,6 +543,8 @@ -(void) viewDidEndLiveResize
       ALLEGRO_INFO("Window finished resizing %d x %d\n", event.display.width, event.display.height);
    }
    _al_event_source_unlock(es);
+   dpy->old_w = NSWidth(content);
+   dpy->old_h = NSWidth(content);
 }
 /* Window switch in/out */
 -(void) windowDidBecomeMain:(NSNotification*) notification
@@ -1512,6 +1514,8 @@ static void init_new_vsync(ALLEGRO_DISPLAY_OSX_WIN *dpy)
 #endif
    display->w = w;
    display->h = h;
+   dpy->old_w = w;
+   dpy->old_h = h;
    _al_event_source_init(&display->es);
    _al_osx_change_cursor(dpy, [NSCursor arrowCursor]);
    dpy->show_cursor = YES;
@@ -2072,6 +2076,10 @@ static bool resize_display_win(ALLEGRO_DISPLAY *d, int w, int h)
    });
    // must be done on the thread the user calls it from, not the main thread
    setup_gl(d);
+   // Only update the old values in response to user-initiated resizes.
+   ALLEGRO_DISPLAY_OSX_WIN *dpy = (ALLEGRO_DISPLAY_OSX_WIN *)d;
+   dpy->old_w = w;
+   dpy->old_h = h;
    return rc;
 }
 
@@ -2458,7 +2466,7 @@ static bool set_display_flag(ALLEGRO_DISPLAY *display, int flag, bool onoff)
                display->flags |= ALLEGRO_MAXIMIZED;
             else
                display->flags &= ~ALLEGRO_MAXIMIZED;
-            [dpy->view maximize];
+            [view maximize];
             break;
          case ALLEGRO_FULLSCREEN_WINDOW:
             if (onoff) {
@@ -2471,12 +2479,8 @@ static bool set_display_flag(ALLEGRO_DISPLAY *display, int flag, bool onoff)
                display->flags |= ALLEGRO_FULLSCREEN_WINDOW;
             } else {
                [view exitFullScreenWindowMode];
-               NSRect sc = [view frame];
-#if MAC_OS_X_VERSION_MIN_REQUIRED >= 1070
-               sc = [win convertRectToBacking: sc];
-#endif
                display->flags &= ~ALLEGRO_FULLSCREEN_WINDOW;
-               resize_display_win_main_thread(display, sc.size.width, sc.size.height);
+               resize_display_win_main_thread(display, dpy->old_w, dpy->old_h);
                [view finishExitingFullScreenWindowMode];
             }
             need_setup_gl = true;