WIP Test enabled window transparency

Author: guusw

wgpu-core/src/device/global.rs

@@ -1946,44 +1946,44 @@ impl Global {
                     available: caps.formats.clone(),
                 });
             }
-            if !caps
-                .composite_alpha_modes
-                .contains(&config.composite_alpha_mode)
-            {
-                let new_alpha_mode = 'alpha: {
-                    // Automatic alpha mode checks.
-                    let fallbacks = match config.composite_alpha_mode {
-                        wgt::CompositeAlphaMode::Auto => &[
-                            wgt::CompositeAlphaMode::Opaque,
-                            wgt::CompositeAlphaMode::Inherit,
-                        ][..],
-                        _ => {
-                            return Err(E::UnsupportedAlphaMode {
-                                requested: config.composite_alpha_mode,
-                                available: caps.composite_alpha_modes.clone(),
-                            });
-                        }
-                    };
-
-                    for &fallback in fallbacks {
-                        if caps.composite_alpha_modes.contains(&fallback) {
-                            break 'alpha fallback;
-                        }
-                    }
-
-                    unreachable!(
-                        "Fallback system failed to choose alpha mode. This is a bug. \
-                                  AlphaMode: {:?}, Options: {:?}",
-                        config.composite_alpha_mode, &caps.composite_alpha_modes
-                    );
-                };
-
-                api_log!(
-                    "Automatically choosing alpha mode by rule {:?}. Chose {new_alpha_mode:?}",
-                    config.composite_alpha_mode
-                );
-                config.composite_alpha_mode = new_alpha_mode;
-            }
+            // if !caps
+            //     .composite_alpha_modes
+            //     .contains(&config.composite_alpha_mode)
+            // {
+            //     let new_alpha_mode = 'alpha: {
+            //         // Automatic alpha mode checks.
+            //         let fallbacks = match config.composite_alpha_mode {
+            //             wgt::CompositeAlphaMode::Auto => &[
+            //                 wgt::CompositeAlphaMode::Opaque,
+            //                 wgt::CompositeAlphaMode::Inherit,
+            //             ][..],
+            //             _ => {
+            //                 return Err(E::UnsupportedAlphaMode {
+            //                     requested: config.composite_alpha_mode,
+            //                     available: caps.composite_alpha_modes.clone(),
+            //                 });
+            //             }
+            //         };
+
+            //         for &fallback in fallbacks {
+            //             if caps.composite_alpha_modes.contains(&fallback) {
+            //                 break 'alpha fallback;
+            //             }
+            //         }
+
+            //         unreachable!(
+            //             "Fallback system failed to choose alpha mode. This is a bug. \
+            //                       AlphaMode: {:?}, Options: {:?}",
+            //             config.composite_alpha_mode, &caps.composite_alpha_modes
+            //         );
+            //     };
+
+            //     api_log!(
+            //         "Automatically choosing alpha mode by rule {:?}. Chose {new_alpha_mode:?}",
+            //         config.composite_alpha_mode
+            //     );
+            //     config.composite_alpha_mode = new_alpha_mode;
+            // }
             if !caps.usage.contains(config.usage) {
                 return Err(E::UnsupportedUsage);
             }

wgpu-types/src/lib.rs

@@ -5408,7 +5408,11 @@ impl Default for SurfaceCapabilities {
         Self {
             formats: Vec::new(),
             present_modes: Vec::new(),
-            alpha_modes: vec![CompositeAlphaMode::Opaque],
+            alpha_modes: vec![
+                CompositeAlphaMode::Opaque,
+                CompositeAlphaMode::PreMultiplied,
+                CompositeAlphaMode::PostMultiplied
+            ],
             usages: TextureUsages::RENDER_ATTACHMENT,
         }
     }