Auto merge of #8997 - dzbarsky:scissor, r=dzbarsky

Implement WebGL scissor method

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components/canvas/webgl_paint_task.rs

@@ -111,6 +111,8 @@ impl WebGLPaintTask {
                 gl::pixel_store_i(name, val),
             CanvasWebGLMsg::PolygonOffset(factor, units) =>
                 gl::polygon_offset(factor, units),
+            CanvasWebGLMsg::Scissor(x, y, width, height) =>
+                gl::scissor(x, y, width, height),
             CanvasWebGLMsg::EnableVertexAttribArray(attrib_id) =>
                 gl::enable_vertex_attrib_array(attrib_id),
             CanvasWebGLMsg::GetAttribLocation(program_id, name, chan) =>

components/canvas_traits/lib.rs

@@ -175,6 +175,7 @@ pub enum CanvasWebGLMsg {
     GetAttribLocation(u32, String, IpcSender<Option<i32>>),
     GetUniformLocation(u32, String, IpcSender<Option<i32>>),
     PolygonOffset(f32, f32),
+    Scissor(i32, i32, i32, i32),
     Hint(u32, u32),
     LineWidth(f32),
     PixelStorei(u32, i32),

components/script/dom/webglrenderingcontext.rs

@@ -906,6 +906,13 @@ impl WebGLRenderingContextMethods for WebGLRenderingContext {
             .unwrap()
     }
 
+    // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.4
+    fn Scissor(&self, x: i32, y: i32, width: i32, height: i32) {
+        self.ipc_renderer
+            .send(CanvasMsg::WebGL(CanvasWebGLMsg::Scissor(x, y, width, height)))
+            .unwrap()
+    }
+
     // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.9
     fn LinkProgram(&self, program: Option<&WebGLProgram>) {
         if let Some(program) = program {

components/script/dom/webidls/WebGLRenderingContext.webidl

@@ -618,7 +618,7 @@ interface WebGLRenderingContextBase
     //void renderbufferStorage(GLenum target, GLenum internalformat,
     //                         GLsizei width, GLsizei height);
     //void sampleCoverage(GLclampf value, GLboolean invert);
-    //void scissor(GLint x, GLint y, GLsizei width, GLsizei height);
+    void scissor(GLint x, GLint y, GLsizei width, GLsizei height);
 
     void shaderSource(WebGLShader? shader, DOMString source);