Add a workaround for #1350

allegro5.cfg

@@ -231,6 +231,15 @@ max_page_size = 0
 # Uncomment if you want only the characters in the cache_text entry to ever be drawn
 # skip_cache_misses = true
 
+[osx]
+
+# If set to false, then Allegro will send ALLEGRO_EVENT_DISPLAY_HALT_DRAWING
+# and ALLEGRO_EVENT_DISPLAY_RESUME_DRAWING events when the user resizes a
+# window. Drawing while resizing ("live resizing") has historically been buggy,
+# so setting this to false allows you to opt out of this behavior and detect
+# when the resize happens.
+allow_live_resize = true
+
 [compatibility]
 
 # Prior to 5.2.4 on Windows you had to manually resize the display when

demos/skater/src/framework.c

@@ -336,6 +336,7 @@ void run_framework(void)
 
          case ALLEGRO_EVENT_DISPLAY_RESUME_DRAWING:
             background_mode = false;
+            al_acknowledge_drawing_resume(screen);
             break;
 
          case ALLEGRO_EVENT_DISPLAY_SWITCH_OUT:

examples/ex_camera.c

@@ -474,6 +474,7 @@ int main(int argc, char **argv)
    ALLEGRO_TIMER *timer;
    ALLEGRO_EVENT_QUEUE *queue;
    int redraw = 0;
+   bool halt_drawing = false;
    char const *skybox_name = NULL;
 
    if (argc > 1) {
@@ -489,6 +490,7 @@ int main(int argc, char **argv)
    al_install_keyboard();
    al_install_mouse();
 
+   al_set_config_value(al_get_system_config(), "osx", "allow_live_resize", "false");
    al_set_new_display_option(ALLEGRO_SAMPLE_BUFFERS, 1, ALLEGRO_SUGGEST);
    al_set_new_display_option(ALLEGRO_SAMPLES, 8, ALLEGRO_SUGGEST);
    al_set_new_display_option(ALLEGRO_DEPTH_SIZE, 16, ALLEGRO_SUGGEST);
@@ -566,12 +568,20 @@ int main(int argc, char **argv)
       else if (event.type == ALLEGRO_EVENT_MOUSE_BUTTON_UP) {
          ex.button[event.mouse.button] = 0;
       }
+      else if (event.type == ALLEGRO_EVENT_DISPLAY_HALT_DRAWING) {
+         halt_drawing = true;
+         al_acknowledge_drawing_halt(display);
+      }
+      else if (event.type == ALLEGRO_EVENT_DISPLAY_RESUME_DRAWING) {
+         halt_drawing = false;
+         al_acknowledge_drawing_resume(display);
+      }
       else if (event.type == ALLEGRO_EVENT_MOUSE_AXES) {
          ex.mouse_dx += event.mouse.dx;
          ex.mouse_dy += event.mouse.dy;
       }
 
-      if (redraw  && al_is_event_queue_empty(queue)) {
+      if (!halt_drawing && redraw && al_is_event_queue_empty(queue)) {
          draw_scene();
 
          al_flip_display();

examples/ex_resize2.c

@@ -20,6 +20,7 @@ int main(int argc, char **argv)
    ALLEGRO_EVENT event;
    ALLEGRO_FONT *font;
    bool redraw;
+   bool halt_drawing;
 
    (void)argc;
    (void)argv;
@@ -31,6 +32,7 @@ int main(int argc, char **argv)
    al_init_image_addon();
    al_init_font_addon();
 
+   al_set_config_value(al_get_system_config(), "osx", "allow_live_resize", "false");
    al_set_new_display_flags(ALLEGRO_RESIZABLE |
       ALLEGRO_GENERATE_EXPOSE_EVENTS);
    display = al_create_display(640, 480);
@@ -51,8 +53,9 @@ int main(int argc, char **argv)
    al_register_event_source(queue, al_get_keyboard_event_source());
 
    redraw = true;
+   halt_drawing = false;
    while (true) {
-      if (redraw && al_is_event_queue_empty(queue)) {
+      if (!halt_drawing && redraw && al_is_event_queue_empty(queue)) {
          al_clear_to_color(al_map_rgb(255, 0, 0));
          al_draw_scaled_bitmap(bmp,
             0, 0, al_get_bitmap_width(bmp), al_get_bitmap_height(bmp),
@@ -81,6 +84,14 @@ int main(int argc, char **argv)
       if (event.type == ALLEGRO_EVENT_DISPLAY_EXPOSE) {
          redraw = true;
       }
+      if (event.type == ALLEGRO_EVENT_DISPLAY_HALT_DRAWING) {
+         halt_drawing = true;
+         al_acknowledge_drawing_halt(display);
+      }
+      if (event.type == ALLEGRO_EVENT_DISPLAY_RESUME_DRAWING) {
+         halt_drawing = false;
+         al_acknowledge_drawing_resume(display);
+      }
       if (event.type == ALLEGRO_EVENT_KEY_DOWN &&
             event.keyboard.keycode == ALLEGRO_KEY_ESCAPE) {
          break;

src/macosx/osxgl.h

@@ -34,6 +34,10 @@ typedef struct ALLEGRO_DISPLAY_OSX_WIN {
    BOOL in_fullscreen;
    BOOL single_buffer;
    CGDisplayModeRef original_mode;
+   BOOL send_halt_events;
+   ALLEGRO_MUTEX *halt_mutex;
+   ALLEGRO_COND *halt_cond;
+   BOOL halt_event_acknowledged;
    /* For new (10.14+) vsyncing. */
    CVDisplayLinkRef display_link;
    ALLEGRO_MUTEX *flip_mutex;

src/macosx/osxgl.m

@@ -235,6 +235,7 @@ -(void) viewDidMoveToWindow;
 -(void) viewWillMoveToWindow: (NSWindow*) newWindow;
 -(void) mouseEntered: (NSEvent*) evt;
 -(void) mouseExited: (NSEvent*) evt;
+-(void) viewWillStartLiveResize;
 -(void) viewDidEndLiveResize;
 /* Window delegate methods */
 -(void) windowDidBecomeMain:(NSNotification*) notification;
@@ -519,6 +520,33 @@ -(void) viewDidChangeBackingProperties
 }
 #endif
 
+-(void) viewWillStartLiveResize
+{
+   ALLEGRO_DISPLAY_OSX_WIN* dpy =  (ALLEGRO_DISPLAY_OSX_WIN*) dpy_ptr;
+   ALLEGRO_EVENT_SOURCE *es = &dpy->parent.es;
+
+   if (dpy->send_halt_events) {
+      al_lock_mutex(dpy->halt_mutex);
+      dpy->halt_event_acknowledged = false;
+      al_unlock_mutex(dpy->halt_mutex);
+
+      _al_event_source_lock(es);
+      if (_al_event_source_needs_to_generate_event(es)) {
+         ALLEGRO_EVENT event;
+         event.display.type = ALLEGRO_EVENT_DISPLAY_HALT_DRAWING;
+         event.display.timestamp = al_get_time();
+         _al_event_source_emit_event(es, &event);
+      }
+      _al_event_source_unlock(es);
+
+      al_lock_mutex(dpy->halt_mutex);
+      while (!dpy->halt_event_acknowledged) {
+         al_wait_cond(dpy->halt_cond, dpy->halt_mutex);
+      }
+      al_unlock_mutex(dpy->halt_mutex);
+   }
+}
+
 -(void) viewDidEndLiveResize
 {
    [super viewDidEndLiveResize];
@@ -541,6 +569,11 @@ -(void) viewDidEndLiveResize
       event.display.height = NSHeight(content);
       _al_event_source_emit_event(es, &event);
       ALLEGRO_INFO("Window finished resizing %d x %d\n", event.display.width, event.display.height);
+
+      if (dpy->send_halt_events) {
+         event.display.type = ALLEGRO_EVENT_DISPLAY_RESUME_DRAWING;
+         _al_event_source_emit_event(es, &event);
+      }
    }
    _al_event_source_unlock(es);
 }
@@ -1102,6 +1135,19 @@ static void init_new_vsync(ALLEGRO_DISPLAY_OSX_WIN *dpy)
    CVDisplayLinkStart(dpy->display_link);
 }
 
+static void init_halt_events(ALLEGRO_DISPLAY_OSX_WIN *dpy)
+{
+   const char* value = al_get_config_value(al_get_system_config(), "osx", "allow_live_resize");
+   if (value && strcmp(value, "false") == 0) {
+      dpy->send_halt_events = true;
+   }
+   else {
+      dpy->send_halt_events = false;
+   }
+   dpy->halt_mutex = al_create_mutex();
+   dpy->halt_cond = al_create_cond();
+}
+
 /* create_display_fs:
  * Create a fullscreen display - capture the display
  */
@@ -1139,6 +1185,7 @@ static void init_new_vsync(ALLEGRO_DISPLAY_OSX_WIN *dpy)
    _al_event_source_init(&display->es);
    dpy->cursor = [[NSCursor arrowCursor] retain];
    dpy->display_id = CGMainDisplayID();
+   init_halt_events(dpy);
 
    /* Get display ID for the requested display */
    if (al_get_new_display_adapter() > 0) {
@@ -1334,6 +1381,7 @@ static void init_new_vsync(ALLEGRO_DISPLAY_OSX_WIN *dpy)
    _al_event_source_init(&dpy->parent.es);
    osx_change_cursor(dpy, [NSCursor arrowCursor]);
    dpy->show_cursor = YES;
+   init_halt_events(dpy);
 
    // Set up a pixel format to describe the mode we want.
    osx_set_opengl_pixelformat_attributes(dpy);
@@ -1513,6 +1561,7 @@ static void init_new_vsync(ALLEGRO_DISPLAY_OSX_WIN *dpy)
    _al_event_source_init(&display->es);
    _al_osx_change_cursor(dpy, [NSCursor arrowCursor]);
    dpy->show_cursor = YES;
+   init_halt_events(dpy);
 
    // Set up a pixel format to describe the mode we want.
    osx_set_opengl_pixelformat_attributes(dpy);
@@ -1799,6 +1848,8 @@ static void destroy_display(ALLEGRO_DISPLAY* d)
       _al_set_current_display_only(NULL);
    }
 
+   al_destroy_cond(dpy->halt_cond);
+   al_destroy_mutex(dpy->halt_mutex);
    if (dpy->flip_mutex) {
       al_destroy_mutex(dpy->flip_mutex);
       al_destroy_cond(dpy->flip_cond);
@@ -2489,6 +2540,15 @@ static bool set_display_flag(ALLEGRO_DISPLAY *display, int flag, bool onoff)
 #endif
 }
 
+static void acknowledge_drawing_halt(ALLEGRO_DISPLAY *display)
+{
+   ALLEGRO_DISPLAY_OSX_WIN *dpy = (ALLEGRO_DISPLAY_OSX_WIN *)display;
+   al_lock_mutex(dpy->halt_mutex);
+   dpy->halt_event_acknowledged = true;
+   al_signal_cond(dpy->halt_cond);
+   al_unlock_mutex(dpy->halt_mutex);
+}
+
 ALLEGRO_DISPLAY_INTERFACE* _al_osx_get_display_driver_win(void)
 {
    static ALLEGRO_DISPLAY_INTERFACE* vt = NULL;
@@ -2519,6 +2579,7 @@ static bool set_display_flag(ALLEGRO_DISPLAY *display, int flag, bool onoff)
       vt->set_display_flag = set_display_flag;
       vt->set_icons = set_icons;
       vt->update_render_state = _al_ogl_update_render_state;
+      vt->acknowledge_drawing_halt = acknowledge_drawing_halt;
       _al_ogl_add_drawing_functions(vt);
       _al_osx_add_clipboard_functions(vt);
    }