webgl: Check shader compilation status on use_program.

components/script/dom/webglprogram.rs

@@ -73,8 +73,19 @@ impl WebGLProgram {
     }
 
     /// glUseProgram
-    pub fn use_program(&self) {
+    pub fn use_program(&self) -> WebGLResult<()> {
+        match self.fragment_shader.get() {
+            Some(ref shader) if shader.successfully_compiled() => {},
+            _ => return Err(WebGLError::InvalidOperation),
+        }
+
+        match self.vertex_shader.get() {
+            Some(ref shader) if shader.successfully_compiled() => {},
+            _ => return Err(WebGLError::InvalidOperation),
+        }
+
         self.renderer.send(CanvasMsg::WebGL(CanvasWebGLMsg::UseProgram(self.id))).unwrap();
+        Ok(())
     }
 
     /// glAttachShader

components/script/dom/webglrenderingcontext.rs

@@ -1004,8 +1004,10 @@ impl WebGLRenderingContextMethods for WebGLRenderingContext {
     // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.9
     fn UseProgram(&self, program: Option<&WebGLProgram>) {
         if let Some(program) = program {
-            program.use_program();
+            match program.use_program() {
-            self.current_program.set(Some(program));
+                Ok(()) => self.current_program.set(Some(program)),
+                Err(e) => self.webgl_error(e),
+            }
         }
     }
 

components/script/dom/webglshader.rs

@@ -147,6 +147,10 @@ impl WebGLShader {
     pub fn set_source(&self, source: DOMString) {
         *self.source.borrow_mut() = Some(source);
     }
+
+    pub fn successfully_compiled(&self) -> bool {
+        self.compilation_status.get() == ShaderCompilationStatus::Succeeded
+    }
 }
 
 impl Drop for WebGLShader {