twn_loop.c: use event watcher for more immediate resize redraw

src/twn_loop.c

@@ -21,6 +21,31 @@
 #include <limits.h>
 
 
+static int event_callback(void *userdata, SDL_Event *event) {
+    switch (event->type) {
+    case SDL_WINDOWEVENT:
+        if (event->window.windowID != ctx.window_id)
+            break;
+
+        switch (event->window.event) {
+        case SDL_WINDOWEVENT_SIZE_CHANGED:
+            ctx.game.window_w = event->window.data1;
+            ctx.game.window_h = event->window.data2;
+            ctx.resync_flag = true;
+            break;
+
+        default:
+            break;
+        }
+
+        break;
+
+    default:
+        break;
+    }
+}
+
+
 static void poll_events(void) {
     SDL_Event e;
 
@@ -163,13 +188,6 @@ static void main_loop(void) {
 
             poll_events();
 
-            if (ctx.game.window_size_has_changed) {
-                Vec2i size;
-                SDL_GetWindowSize(ctx.window, &size.x, &size.y);
-                ctx.game.window_w = size.x;
-                ctx.game.window_h = size.y;
-            }
-
             input_state_update(&ctx.game.input);
 
             game_object_tick();
@@ -478,6 +496,9 @@ static bool initialize(void) {
     ctx.game.window_w = (int)ctx.base_render_width;
     ctx.game.window_h = (int)ctx.base_render_height;
 
+    /* add a watcher for immediate updates on window size */
+    SDL_AddEventWatch(event_callback, NULL);
+
     /* audio initialization */
     {