Support dual source blending

wgpu-core/src/device/resource.rs

@@ -2714,8 +2714,8 @@ impl<A: HalApi> Device<A> {
                             blend_mode.alpha.dst_factor,
                         ] {
                             if factor.ref_second_blend_source() {
+                                self.require_features(wgt::Features::DUAL_SOURCE_BLENDING)?;
                                 if i == 0 {
-                                    self.require_features(wgt::Features::DUAL_SOURCE_BLENDING)?;
                                     pipeline_expects_dual_source_blending = true;
                                     break;
                                 } else {
@@ -2831,14 +2831,6 @@ impl<A: HalApi> Device<A> {
                         error,
                     })?;
                 validated_stages |= flag;
-
-                let dual_source = interface.has_dual_source_blending_entry_point();
-                if !pipeline_expects_dual_source_blending && dual_source {
-                    return Err(pipeline::CreateRenderPipelineError::ShaderExpectsPipelineToUseDualSourceBlending);
-                }
-                if pipeline_expects_dual_source_blending && !dual_source {
-                    return Err(pipeline::CreateRenderPipelineError::PipelineExpectsShaderToUseDualSourceBlending);
-                }
             }
 
             hal::ProgrammableStage {
@@ -2890,8 +2882,12 @@ impl<A: HalApi> Device<A> {
                 }
 
                 if let Some(ref interface) = shader_module.interface {
-                    shader_expects_dual_source_blending =
-                        interface.is_fragment_entry_dual_source(fragment).expect("Internal error: Fragment entrypoint should not be set in function if not present in shader interface");
+                    shader_expects_dual_source_blending = interface
+                        .fragment_uses_dual_source_blending(&fragment.stage.entry_point)
+                        .map_err(|error| pipeline::CreateRenderPipelineError::Stage {
+                            stage: flag,
+                            error,
+                        })?;
                 }
 
                 Some(hal::ProgrammableStage {

wgpu-core/src/validation.rs

@@ -1179,24 +1179,14 @@ impl Interface {
         Ok(outputs)
     }
 
-    pub fn has_dual_source_blending_entry_point(&self) -> bool {
-        self.entry_points
-            .values()
-            .any(|point| point.dual_source_blending)
-    }
-    pub fn is_fragment_entry_dual_source<'a>(
+    pub fn fragment_uses_dual_source_blending(
         &self,
-        fragment: &crate::pipeline::FragmentState<'a>,
+        entry_point_name: &str,
     ) -> Result<bool, StageError> {
-        if let Some(entry_point) = self.entry_points.get(&(
-            naga::ShaderStage::Fragment,
-            String::from(fragment.stage.entry_point.as_ref()),
-        )) {
-            Ok(entry_point.dual_source_blending)
-        } else {
-            Err(StageError::MissingEntryPoint(String::from(
-                fragment.stage.entry_point.as_ref(),
-            )))
-        }
+        let pair = (naga::ShaderStage::Fragment, entry_point_name.to_string());
+        self.entry_points
+            .get(&pair)
+            .ok_or(StageError::MissingEntryPoint(pair.1))
+            .map(|ep| ep.dual_source_blending)
     }
 }

wgpu-hal/src/metal/adapter.rs

@@ -796,7 +796,6 @@ impl super::PrivateCapabilities {
                 None
             },
             timestamp_query_support,
-            dual_source_blending: version.at_least((11, 0), (14, 0), os_is_mac),
         }
     }
 
@@ -836,7 +835,7 @@ impl super::PrivateCapabilities {
         );
         features.set(
             F::DUAL_SOURCE_BLENDING,
-            self.msl_version >= MTLLanguageVersion::V1_2,
+            self.msl_version >= MTLLanguageVersion::V1_2 && self.dual_source_blending,
         );
         features.set(F::TEXTURE_COMPRESSION_ASTC, self.format_astc);
         features.set(F::TEXTURE_COMPRESSION_ASTC_HDR, self.format_astc_hdr);

wgpu-hal/src/metal/conv.rs

@@ -152,8 +152,6 @@ pub fn map_blend_factor(factor: wgt::BlendFactor) -> metal::MTLBlendFactor {
         Bf::OneMinusDstAlpha => OneMinusDestinationAlpha,
         Bf::Constant => BlendColor,
         Bf::OneMinusConstant => OneMinusBlendColor,
-        //Bf::ConstantAlpha => BlendAlpha,
-        //Bf::OneMinusConstantAlpha => OneMinusBlendAlpha,
         Bf::SrcAlphaSaturated => SourceAlphaSaturated,
         Bf::Src1 => Source1Color,
         Bf::OneMinusSrc1 => OneMinusSource1Color,

wgpu-types/src/lib.rs

@@ -792,8 +792,6 @@ bitflags::bitflags! {
         /// - Vulkan (with dualSrcBlend)
         /// - DX12
         const DUAL_SOURCE_BLENDING = 1 << 63;
-
-        // no more space left
     }
 }