Implement the new checks for readonly stencils

CHANGELOG.md

@@ -45,6 +45,7 @@ Bottom level categories:
 #### WebGPU
 
 - Implement `CommandEncoder::clear_buffer`. By @raphlinus in [#3426](https://github.com/gfx-rs/wgpu/pull/3426)
+- Implement the new checks for readonly stencils. By @JCapucho in [#3443](https://github.com/gfx-rs/wgpu/pull/3443)
 
 #### Vulkan
 

wgpu-core/src/device/mod.rs

@@ -3072,7 +3072,7 @@ impl<A: HalApi> Device<A> {
  if !ds.is_depth_read_only() {
  flags |= pipeline::PipelineFlags::WRITES_DEPTH;
  }
- if !ds.is_stencil_read_only() {
+ if !ds.is_stencil_read_only(desc.primitive.cull_mode) {
  flags |= pipeline::PipelineFlags::WRITES_STENCIL;
  }
  }

wgpu-hal/src/vulkan/device.rs

@@ -1607,7 +1607,7 @@ impl crate::Device<super::Api> for super::Device {
  let mut vk_depth_stencil = vk::PipelineDepthStencilStateCreateInfo::builder();
  if let Some(ref ds) = desc.depth_stencil {
  let vk_format = self.shared.private_caps.map_texture_format(ds.format);
- let vk_layout = if ds.is_read_only() {
+ let vk_layout = if ds.is_read_only(desc.primitive.cull_mode) {
  vk::ImageLayout::DEPTH_STENCIL_READ_ONLY_OPTIMAL
  } else {
  vk::ImageLayout::DEPTH_STENCIL_ATTACHMENT_OPTIMAL

wgpu-types/src/lib.rs

@@ -3289,8 +3289,19 @@ impl StencilState {
  && (self.read_mask != 0 || self.write_mask != 0)
  }
  /// Returns true if the state doesn't mutate the target values.
- pub fn is_read_only(&self) -> bool {
- self.write_mask == 0
+ pub fn is_read_only(&self, cull_mode: Option<Face>) -> bool {
+ // The rules are defined in step 7 of the "Device timeline initialization steps"
+ // subsection of the "Render Pipeline Creation" section of WebGPU
+ // (link to the section: https://gpuweb.github.io/gpuweb/#render-pipeline-creation)
+
+ if self.write_mask == 0 {
+ return true;
+ }
+
+ let front_ro = cull_mode == Some(Face::Front) || self.front.is_read_only();
+ let back_ro = cull_mode == Some(Face::Back) || self.back.is_read_only();
+
+ front_ro && back_ro
  }
  /// Returns true if the stencil state uses the reference value for testing.
  pub fn needs_ref_value(&self) -> bool {
@@ -3380,13 +3391,13 @@ impl DepthStencilState {
  }
 
  /// Returns true if the state doesn't mutate the stencil.
- pub fn is_stencil_read_only(&self) -> bool {
- self.stencil.is_read_only()
+ pub fn is_stencil_read_only(&self, cull_mode: Option<Face>) -> bool {
+ self.stencil.is_read_only(cull_mode)
  }
 
  /// Returns true if the state doesn't mutate either depth or stencil of the target.
- pub fn is_read_only(&self) -> bool {
- self.is_depth_read_only() && self.is_stencil_read_only()
+ pub fn is_read_only(&self, cull_mode: Option<Face>) -> bool {
+ self.is_depth_read_only() && self.is_stencil_read_only(cull_mode)
  }
 }
 
@@ -3476,6 +3487,13 @@ impl StencilFaceState {
  || self.depth_fail_op == StencilOperation::Replace
  || self.pass_op == StencilOperation::Replace
  }
+
+ /// Returns true if the face state doesn't mutate the target values.
+ pub fn is_read_only(&self) -> bool {
+ self.pass_op == StencilOperation::Keep
+ && self.depth_fail_op == StencilOperation::Keep
+ && self.fail_op == StencilOperation::Keep
+ }
 }
 
 impl Default for StencilFaceState {