Split Blendability and Filterability into Two Different TextureFormatFeatureFlags (#3012)

* Split Blendability and Filterability into Two Different TextureFormatFeatureFlags

* Update CHANGELOG.md

* Split out individual booleans to improve readability

* Make sure blendablity is correctly set for guaranteed format features of WebGPU

* Cargo fmt

Co-authored-by: Xander Warnez <xander.warnez@materialise.be>
Co-authored-by: Connor Fitzgerald <connorwadefitzgerald@gmail.com>

Author: 3 people

CHANGELOG.md

@@ -72,6 +72,7 @@ SurfaceConfiguration {
 ### Added/New Features
 
 - Add `Buffer::size()` and `Buffer::usage()`; by @kpreid in [#2923](https://github.com/gfx-rs/wgpu/pull/2923)
+- Split Blendability and Filterability into Two Different TextureFormatFeatureFlags; by @stakka in [#3012](https://github.com/gfx-rs/wgpu/pull/3012)
 - Expose `alpha_mode` on SurfaceConfiguration, by @jinleili in [#2836](https://github.com/gfx-rs/wgpu/pull/2836)
 - Introduce fields for driver name and info in `AdapterInfo`, by @i509VCB in [#3037](https://github.com/gfx-rs/wgpu/pull/3037)
 

wgpu-core/src/device/mod.rs

@@ -2625,7 +2625,14 @@ impl<A: HalApi> Device<A> {
                     {
                         break Some(pipeline::ColorStateError::FormatNotRenderable(cs.format));
                     }
-                    if cs.blend.is_some() && !format_features.flags.contains(Tfff::FILTERABLE) {
+                    let blendable = format_features.flags.contains(Tfff::BLENDABLE);
+                    let filterable = format_features.flags.contains(Tfff::FILTERABLE);
+                    let adapter_specific = self
+                        .features
+                        .contains(wgt::Features::TEXTURE_ADAPTER_SPECIFIC_FORMAT_FEATURES);
+                    // according to WebGPU specifications the texture needs to be [`TextureFormatFeatureFlags::FILTERABLE`]
+                    // if blending is set - use [`Features::TEXTURE_ADAPTER_SPECIFIC_FORMAT_FEATURES`] to elude this limitation
+                    if cs.blend.is_some() && (!blendable || (!filterable && !adapter_specific)) {
                         break Some(pipeline::ColorStateError::FormatNotBlendable(cs.format));
                     }
                     if !hal::FormatAspects::from(cs.format).contains(hal::FormatAspects::COLOR) {

wgpu-core/src/instance.rs

@@ -249,14 +249,14 @@ impl<A: HalApi> Adapter<A> {
             caps.contains(Tfc::STORAGE_READ_WRITE),
         );
 
-        // We are currently taking the filtering and blending together,
-        // but we may reconsider this in the future if there are formats
-        // in the wild for which these two capabilities do not match.
         flags.set(
             wgt::TextureFormatFeatureFlags::FILTERABLE,
-            caps.contains(Tfc::SAMPLED_LINEAR)
-                && (!caps.contains(Tfc::COLOR_ATTACHMENT)
-                    || caps.contains(Tfc::COLOR_ATTACHMENT_BLEND)),
+            caps.contains(Tfc::SAMPLED_LINEAR),
+        );
+
+        flags.set(
+            wgt::TextureFormatFeatureFlags::BLENDABLE,
+            caps.contains(Tfc::COLOR_ATTACHMENT_BLEND),
         );
 
         flags.set(

wgpu-types/src/lib.rs

@@ -1662,6 +1662,8 @@ bitflags::bitflags! {
         /// When used as a STORAGE texture, then a texture with this format can be written to with atomics.
         // TODO: No access flag exposed as of writing
         const STORAGE_ATOMICS = 1 << 4;
+        /// If not present, the texture can't be blended into the render target.
+        const BLENDABLE = 1 << 5;
     }
 }
 
@@ -2288,10 +2290,12 @@ impl TextureFormat {
         };
 
         let mut flags = msaa_flags;
+        let filterable_sample_type = sample_type == TextureSampleType::Float { filterable: true };
         flags.set(
             TextureFormatFeatureFlags::FILTERABLE,
-            sample_type == TextureSampleType::Float { filterable: true },
+            filterable_sample_type,
         );
+        flags.set(TextureFormatFeatureFlags::BLENDABLE, filterable_sample_type);
 
         TextureFormatInfo {
             required_features,