From 11426e862852ebe058f4b518aadfc18cf075cb7b Mon Sep 17 00:00:00 2001
From: Jakub Panek <me@panekj.dev>
Date: Mon, 13 May 2024 09:58:09 +0200
Subject: [PATCH] auto choose supported CompositeAlphaMode capability

---
 vger/src/lib.rs | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/vger/src/lib.rs b/vger/src/lib.rs
index 3c604954..5ec7981a 100644
--- a/vger/src/lib.rs
+++ b/vger/src/lib.rs
@@ -79,19 +79,36 @@ impl VgerRenderer {
         let queue = Arc::new(queue);
 
         let surface_caps = surface.get_capabilities(&adapter);
+
+        tracing::trace!("surface caps: {surface_caps:?}");
+
         let texture_format = surface_caps
             .formats
             .into_iter()
             .find(|it| matches!(it, TextureFormat::Rgba8Unorm | TextureFormat::Bgra8Unorm))
             .ok_or_else(|| anyhow::anyhow!("surface should support Rgba8Unorm or Bgra8Unorm"))?;
 
+        let alpha_mode = if surface_caps
+            .alpha_modes
+            .contains(&wgpu::CompositeAlphaMode::PostMultiplied)
+        {
+            wgpu::CompositeAlphaMode::PostMultiplied
+        } else if surface_caps
+            .alpha_modes
+            .contains(&wgpu::CompositeAlphaMode::PreMultiplied)
+        {
+            wgpu::CompositeAlphaMode::PreMultiplied
+        } else {
+            wgpu::CompositeAlphaMode::Auto
+        };
+
         let config = wgpu::SurfaceConfiguration {
             usage: wgpu::TextureUsages::RENDER_ATTACHMENT,
             format: texture_format,
             width,
             height,
             present_mode: wgpu::PresentMode::Fifo,
-            alpha_mode: wgpu::CompositeAlphaMode::Auto,
+            alpha_mode,
             view_formats: vec![],
             desired_maximum_frame_latency: 2,
         };