Skip invariant for gl_FragCoord on WebGL2 (#2254)

src/back/glsl/mod.rs

@@ -1264,11 +1264,27 @@ impl<'a, W: Write> Writer<'a, W> {
  } => (location, interpolation, sampling),
  crate::Binding::BuiltIn(built_in) => {
  if let crate::BuiltIn::Position { invariant: true } = built_in {
- writeln!(
- self.out,
- "invariant {};",
- glsl_built_in(built_in, output, self.options.version.is_webgl())
- )?;
+ match (self.options.version, self.entry_point.stage) {
+ (
+ Version::Embedded {
+ version: 300,
+ is_webgl: true,
+ },
+ ShaderStage::Fragment,
+ ) => {
+ // `invariant gl_FragCoord` is not allowed in WebGL2 and possibly
+ // OpenGL ES in general (waiting on confirmation).
+ //
+ // See https://github.com/KhronosGroup/WebGL/issues/3518
+ }
+ _ => {
+ writeln!(
+ self.out,
+ "invariant {};",
+ glsl_built_in(built_in, output, self.options.version.is_webgl())
+ )?;
+ }
+ }
  }
  return Ok(());
  }

tests/in/invariant.param.ron

@@ -0,0 +1,11 @@
+(
+ glsl: (
+ version: Embedded (
+ version: 300,
+ is_webgl: true
+ ),
+ writer_flags: (bits: 0),
+ binding_map: {},
+ zero_initialize_workgroup_memory: true,
+ ),
+)

tests/in/invariant.wgsl

@@ -0,0 +1,7 @@
+@vertex
+fn vs() -> @builtin(position) @invariant vec4<f32> {
+ return vec4<f32>(0.0);
+}
+
+@fragment
+fn fs(@builtin(position) @invariant position: vec4<f32>) { }

tests/out/glsl/invariant.frag_main.Fragment.glsl

@@ -0,0 +1,11 @@
+#version 300 es
+
+precision highp float;
+precision highp int;
+
+
+void main() {
+ vec4 position = gl_FragCoord;
+ return;
+}
+

tests/out/glsl/invariant.fs.Fragment.glsl

@@ -0,0 +1,11 @@
+#version 300 es
+
+precision highp float;
+precision highp int;
+
+
+void main() {
+ vec4 position = gl_FragCoord;
+ return;
+}
+

tests/out/glsl/invariant.vs.Vertex.glsl

@@ -0,0 +1,12 @@
+#version 300 es
+
+precision highp float;
+precision highp int;
+
+invariant gl_Position;
+
+void main() {
+ gl_Position = vec4(0.0);
+ return;
+}
+

tests/snapshots.rs

@@ -558,6 +558,7 @@ fn convert_wgsl() {
  ),
  ("sprite", Targets::SPIRV),
  ("force_point_size_vertex_shader_webgl", Targets::GLSL),
+ ("invariant", Targets::GLSL),
  ];
 
  for &(name, targets) in inputs.iter() {