From b6ef6236438141e3fab9644c6b29e270d79c2553 Mon Sep 17 00:00:00 2001
From: Julian Orth <ju.orth@gmail.com>
Date: Fri, 5 Sep 2025 19:35:32 +0200
Subject: [PATCH] metal: disable direct scanout if blending would change the
 appearance

---
 src/backends/metal/present.rs | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/backends/metal/present.rs b/src/backends/metal/present.rs
index 258627ac..d6e162a7 100644
--- a/src/backends/metal/present.rs
+++ b/src/backends/metal/present.rs
@@ -626,6 +626,7 @@ impl MetalConnector {
         &self,
         pass: &GfxRenderPass,
         plane: &Rc<MetalPlane>,
+        blend_cd: &Rc<ColorDescription>,
         cd: &Rc<ColorDescription>,
     ) -> Option<DirectScanoutData> {
         let ct = 'ct: {
@@ -647,6 +648,10 @@ impl MetalConnector {
                 // Direct scanout requires embeddable color descriptions.
                 return None;
             }
+            if !ct.opaque && !ct.cd.embeds_into(blend_cd) {
+                // Blending changes the appearance of translucent buffers.
+                return None;
+            }
             if ct.alpha.is_some() {
                 // Direct scanout with alpha factor is not supported.
                 return None;
@@ -818,7 +823,7 @@ impl MetalConnector {
             && self.dev.is_render_device();
         let mut direct_scanout_data = None;
         if try_direct_scanout {
-            direct_scanout_data = self.prepare_direct_scanout(&latched.pass, plane, cd);
+            direct_scanout_data = self.prepare_direct_scanout(&latched.pass, plane, blend_cd, cd);
         }
         let direct_scanout_active = direct_scanout_data.is_some();
         if self.direct_scanout_active.replace(direct_scanout_active) != direct_scanout_active {