Merge #2174

2174: metal: Hack to fix the first frame of a swapchain r=kvark a=scoopr

The freeing up of the drawable now checks if there is anything to free
from the has_swapchain boolean.

The boolean is totally a hack, and might have some edge-cases where it
is wrong, but this happens to fix warnings and red-frame flashes
(present of not drawn frame) from the quad example, with the resizing
still working.

Fixes #issue
PR checklist:
- [ ] `make` succeeds (on *nix)
- [ ] `make reftests` succeeds
- [ ] tested examples with the following backends:


Co-authored-by: Mikko Lehtonen <[email protected]>

Author: bors[bot]

src/backend/metal/src/lib.rs

@@ -144,6 +144,7 @@ impl Instance {
         window::Surface {
             inner: Arc::new(self.create_from_nsview(nsview)),
             apply_pixel_scale: false,
+            has_swapchain: false
         }
     }
 
@@ -153,6 +154,7 @@ impl Instance {
         window::Surface {
             inner: Arc::new(self.create_from_nsview(window.get_nsview())),
             apply_pixel_scale: true,
+            has_swapchain: false,
         }
     }
 }

src/backend/metal/src/window.rs

@@ -22,6 +22,7 @@ pub type CAMetalLayer = *mut Object;
 pub struct Surface {
     pub(crate) inner: Arc<SurfaceInner>,
     pub(crate) apply_pixel_scale: bool,
+    pub(crate) has_swapchain: bool
 }
 
 #[derive(Debug)]
@@ -274,14 +275,20 @@ impl Device {
                     let texture: &metal::TextureRef = msg_send![drawable, texture];
                     (drawable, texture)
                 };
-                if index == 0 {
+                trace!("\tframe[{}] = {:?}", index, texture);
+
+                let drawable = if index == 0 && surface.has_swapchain {
                     // when resizing, this trick frees up the currently shown frame
+                    // HACK: the has_swapchain is unfortunate, and might not be
+                    //       correct in all cases.
                     drawable.present();
-                }
-                trace!("\tframe[{}] = {:?}", index, texture);
+                    None
+                } else {
+                    Some(drawable.to_owned())
+                };
                 Frame {
                     inner: Mutex::new(FrameInner {
-                        drawable: Some(drawable.to_owned()),
+                        drawable: drawable,
                         available: true,
                         last_frame: 0,
                     }),
@@ -307,6 +314,8 @@ impl Device {
             })
             .collect();
 
+        surface.has_swapchain = true;
+
         let swapchain = Swapchain {
             frames: Arc::new(frames),
             surface: surface.inner.clone(),
@@ -315,6 +324,7 @@ impl Device {
             image_ready_callbacks: Vec::new(),
         };
 
+
         (swapchain, Backbuffer::Images(images))
     }
 }