Update platform macos for handling alt tab better (but it still has issues I think)

src/platform/platform_macos.mm

@@ -52,6 +52,14 @@ static PlatformWindow *g_current_window = nullptr;
 ////////////////////////////////
 // Objective-C helper classes
 
+@interface ASmplAppDelegate : NSObject <NSApplicationDelegate>
+@end
+
+@implementation ASmplAppDelegate
+- (void)applicationDidFinishLaunching:(NSNotification *)notification { (void)notification; }
+- (BOOL)applicationShouldTerminateAfterLastWindowClosed:(NSApplication *)sender { (void)sender; return YES; }
+@end
+
 @interface ASmplWindowDelegate : NSObject <NSWindowDelegate>
 @end
 
@@ -255,10 +263,17 @@ static ASmplMenuTarget *g_menu_target = nil;
 // Public API
 
 PlatformWindow *platform_create_window(PlatformWindowDesc *desc) {
-    // Ensure NSApplication is initialized
+    // Ensure NSApplication is initialized and properly launched
     [NSApplication sharedApplication];
     [NSApp setActivationPolicy:NSApplicationActivationPolicyRegular];
 
+    static ASmplAppDelegate *app_delegate = nil;
+    if (!app_delegate) {
+        app_delegate = [[ASmplAppDelegate alloc] init];
+        [NSApp setDelegate:app_delegate];
+        [NSApp finishLaunching];
+    }
+
     NSRect content_rect = NSMakeRect(0, 0, desc->width, desc->height);
 
     NSWindow *ns_window = [[NSWindow alloc]
@@ -310,12 +325,22 @@ void platform_destroy_window(PlatformWindow *window) {
 
 B32 platform_poll_events(PlatformWindow *window) {
     @autoreleasepool {
+        // When the app is not active (e.g. during Cmd+Tab away), block until
+        // an event arrives instead of spinning.  This keeps CPU near zero while
+        // backgrounded and lets macOS handle the app-switch animation smoothly.
+        BOOL is_active = [NSApp isActive];
+        NSDate *deadline = is_active ? nil : [NSDate distantFuture];
+
         NSEvent *event;
         while ((event = [NSApp nextEventMatchingMask:NSEventMaskAny
-                                           untilDate:nil
+                                           untilDate:deadline
                                               inMode:NSDefaultRunLoopMode
                                              dequeue:YES])) {
             [NSApp sendEvent:event];
+            // After processing one event while backgrounded, switch to
+            // non-blocking drain so we handle any remaining queued events
+            // (including the activation event that will flip isActive).
+            deadline = nil;
         }
     }
     return !window->should_close;

src/renderer/renderer_metal.mm

@@ -539,7 +539,8 @@ Renderer *renderer_create(RendererDesc *desc) {
     layer.device = r->device;
     layer.pixelFormat = MTLPixelFormatBGRA8Unorm;
     layer.framebufferOnly = YES;
-    layer.maximumDrawableCount = NUM_BACK_BUFFERS;
+    layer.displaySyncEnabled = YES;
+    layer.maximumDrawableCount = 3;
 
     NSWindow *window = [view window];
     r->backing_scale = (F32)[window backingScaleFactor];