Add support for WebGL2 GetFragDataLocation

Adds support for the `GetFragDataLocation` WebGL2 call.

See: https://www.khronos.org/registry/webgl/specs/latest/2.0/#3.7.7

components/canvas/Cargo.toml

@@ -35,7 +35,7 @@ raqote = {git = "https://github.com/jrmuizel/raqote"}
 time = { version = "0.1.0", optional = true }
 pixels = {path = "../pixels"}
 servo_config = {path = "../config"}
-sparkle = "0.1.20"
+sparkle = "0.1.22"
 webrender = {git = "https://github.com/servo/webrender"}
 webrender_api = {git = "https://github.com/servo/webrender"}
 webrender_traits = {path = "../webrender_traits"}

components/canvas/webgl_thread.rs

@@ -1287,6 +1287,12 @@ impl WebGLImpl {
                 Self::shader_precision_format(gl, shader_type, precision_type, chan)
             },
             WebGLCommand::GetExtensions(ref chan) => Self::get_extensions(gl, chan),
+            WebGLCommand::GetFragDataLocation(program_id, ref name, ref sender) => {
+                let location =
+                    gl.get_frag_data_location(program_id.get(), &to_name_in_compiled_shader(name));
+                assert!(location >= 0);
+                sender.send(location).unwrap();
+            },
             WebGLCommand::GetUniformLocation(program_id, ref name, ref chan) => {
                 Self::uniform_location(gl, program_id, &name, chan)
             },

components/canvas_traits/webgl.rs

@@ -305,6 +305,7 @@ pub enum WebGLCommand {
     FramebufferTexture2D(u32, u32, u32, Option<WebGLTextureId>, i32),
     GetExtensions(WebGLSender<String>),
     GetShaderPrecisionFormat(u32, u32, WebGLSender<(i32, i32, i32)>),
+    GetFragDataLocation(WebGLProgramId, String, WebGLSender<i32>),
     GetUniformLocation(WebGLProgramId, String, WebGLSender<i32>),
     GetShaderInfoLog(WebGLShaderId, WebGLSender<String>),
     GetProgramInfoLog(WebGLProgramId, WebGLSender<String>),

components/script/dom/webgl2renderingcontext.rs

@@ -1467,6 +1467,12 @@ impl WebGL2RenderingContextMethods for WebGL2RenderingContext {
         self.base.GetAttribLocation(program, name)
     }
 
+    /// https://www.khronos.org/registry/webgl/specs/latest/2.0/#3.7.7
+    fn GetFragDataLocation(&self, program: &WebGLProgram, name: DOMString) -> i32 {
+        handle_potential_webgl_error!(self.base, self.base.validate_ownership(program), return -1);
+        handle_potential_webgl_error!(self.base, program.get_frag_data_location(name), -1)
+    }
+
     /// https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.9
     fn GetProgramInfoLog(&self, program: &WebGLProgram) -> Option<DOMString> {
         self.base.GetProgramInfoLog(program)

components/script/dom/webglprogram.rs

@@ -365,6 +365,30 @@ impl WebGLProgram {
         Ok(location)
     }
 
+    /// glGetFragDataLocation
+    pub fn get_frag_data_location(&self, name: DOMString) -> WebGLResult<i32> {
+        if !self.is_linked() || self.is_deleted() {
+            return Err(WebGLError::InvalidOperation);
+        }
+
+        if !validate_glsl_name(&name)? {
+            return Ok(-1);
+        }
+        if name.starts_with("gl_") {
+            return Ok(-1);
+        }
+
+        let (sender, receiver) = webgl_channel().unwrap();
+        self.upcast::<WebGLObject>()
+            .context()
+            .send_command(WebGLCommand::GetFragDataLocation(
+                self.id,
+                name.into(),
+                sender,
+            ));
+        Ok(receiver.recv().unwrap())
+    }
+
     /// glGetUniformLocation
     pub fn get_uniform_location(
         &self,

components/script/dom/webidls/WebGL2RenderingContext.webidl

@@ -422,7 +422,7 @@ interface mixin WebGL2RenderingContextBase
   //                              optional GLuint srcLengthOverride = 0);
 
   /* Programs and shaders */
-  // [WebGLHandlesContextLoss] GLint getFragDataLocation(WebGLProgram program, DOMString name);
+  [WebGLHandlesContextLoss] GLint getFragDataLocation(WebGLProgram program, DOMString name);
 
   /* Uniforms */
   void uniform1ui(WebGLUniformLocation? location, GLuint v0);