From e81fb6e7214094e0bd14bb61e87de8e9a7157e6a Mon Sep 17 00:00:00 2001
From: Wez Furlong <wez@wezfurlong.org>
Date: Thu, 6 May 2021 19:15:14 -0700
Subject: [PATCH] make alpha work on macos

---
 window/examples/wgpu.rs       | 13 +++++++++++++
 window/src/os/macos/window.rs | 24 +++++++++++-------------
 2 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/window/examples/wgpu.rs b/window/examples/wgpu.rs
index 0d9208728..04ecc1d40 100644
--- a/window/examples/wgpu.rs
+++ b/window/examples/wgpu.rs
@@ -1,6 +1,7 @@
 use ::window::*;
 use anyhow::Context;
 use promise::spawn::spawn;
+use raw_window_handle::{HasRawWindowHandle, RawWindowHandle};
 
 pub struct GpuContext {
     pub swap_chain: wgpu::SwapChain,
@@ -227,6 +228,18 @@ async fn spawn_window() -> anyhow::Result<()> {
                 is_full_screen: _,
             } => {
                 state.resize(dimensions);
+                #[cfg(target_os = "macos")]
+                if let RawWindowHandle::MacOS(h) = win.raw_window_handle() {
+                    use cocoa::base::{id, NO};
+                    use objc::*;
+                    unsafe {
+                        // Allow transparency, as the default for Metal is opaque
+                        let layer: id = msg_send![h.ns_view as id, layer];
+                        let () = msg_send![layer, setOpaque: NO];
+                    }
+
+                    state.paint()?;
+                }
             }
             WindowEvent::MouseEvent(event) => {
                 state.cursor_pos = event.coords;
diff --git a/window/src/os/macos/window.rs b/window/src/os/macos/window.rs
index 2b0a01f6d..a0b2229cb 100644
--- a/window/src/os/macos/window.rs
+++ b/window/src/os/macos/window.rs
@@ -17,8 +17,9 @@ use cocoa::appkit::{
     NSWindowStyleMask,
 };
 use cocoa::base::*;
-use cocoa::foundation::NSAutoreleasePool;
-use cocoa::foundation::{NSArray, NSNotFound, NSPoint, NSRect, NSSize, NSUInteger};
+use cocoa::foundation::{
+    NSArray, NSAutoreleasePool, NSInteger, NSNotFound, NSPoint, NSRect, NSSize, NSUInteger,
+};
 use config::ConfigHandle;
 use core_foundation::base::{CFTypeID, TCFType};
 use core_foundation::bundle::{CFBundleGetBundleWithIdentifier, CFBundleGetFunctionPointerForName};
@@ -39,6 +40,9 @@ use std::rc::Rc;
 use std::str::FromStr;
 use std::time::Instant;
 
+#[allow(non_upper_case_globals)]
+const NSViewLayerContentsPlacementTopLeft: NSInteger = 11;
+
 fn round_away_from_zerof(value: f64) -> f64 {
     if value > 0. {
         value.max(1.).round()
@@ -189,17 +193,6 @@ impl GlContextPair {
             }
         };
 
-        #[allow(non_upper_case_globals)]
-        unsafe {
-            use cocoa::foundation::NSInteger;
-            const NSViewLayerContentsPlacementTopLeft: NSInteger = 11;
-
-            let () = msg_send![
-                view,
-                setLayerContentsPlacement: NSViewLayerContentsPlacementTopLeft
-            ];
-        }
-
         Ok(Self { context, backend })
     }
 }
@@ -455,6 +448,11 @@ impl Window {
             view.initWithFrame_(rect);
             view.setAutoresizingMask_(NSViewHeightSizable | NSViewWidthSizable);
 
+            let () = msg_send![
+                *view,
+                setLayerContentsPlacement: NSViewLayerContentsPlacementTopLeft
+            ];
+
             window.setContentView_(*view);
             window.setDelegate_(*view);