The Tor Browser: toolkit/devtools/server/actors/webgl.js@129ffea94266 (annotated)

toolkit/devtools/server/actors/webgl.js@129ffea94266 (annotated)

toolkit/devtools/server/actors/webgl.js

Sat, 03 Jan 2015 20:18:00 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Sat, 03 Jan 2015 20:18:00 +0100
branch: TOR_BUG_3246
changeset 7: 129ffea94266
permissions: -rw-r--r--

Conditionally enable double key logic according to:
private browsing mode or privacy.thirdparty.isolate preference and
implement in GetCookieStringCommon and FindCookie where it counts...
With some reservations of how to convince FindCookie users to test
condition and pass a nullptr when disabling double key logic.

 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 "use strict";
 const {Cc, Ci, Cu, Cr} = require("chrome");
 const events = require("sdk/event/core");
 const protocol = require("devtools/server/protocol");
 const { ContentObserver } = require("devtools/content-observer");
 const { on, once, off, emit } = events;
 const { method, Arg, Option, RetVal } = protocol;
 const WEBGL_CONTEXT_NAMES = ["webgl", "experimental-webgl", "moz-webgl"];
 // These traits are bit masks. Make sure they're powers of 2.
 const PROGRAM_DEFAULT_TRAITS = 0;
 const PROGRAM_BLACKBOX_TRAIT = 1;
 const PROGRAM_HIGHLIGHT_TRAIT = 2;
 exports.register = function(handle) {
   handle.addTabActor(WebGLActor, "webglActor");
 }
 exports.unregister = function(handle) {
   handle.removeTabActor(WebGLActor);
 }
 /**
  * A WebGL Shader contributing to building a WebGL Program.
  * You can either retrieve, or compile the source of a shader, which will
  * automatically inflict the necessary changes to the WebGL state.
  */
 let ShaderActor = protocol.ActorClass({
   typeName: "gl-shader",
   /**
    * Create the shader actor.
    *
    * @param DebuggerServerConnection conn
    *        The server connection.
    * @param WebGLProgram program
    *        The WebGL program being linked.
    * @param WebGLShader shader
    *        The cooresponding vertex or fragment shader.
    * @param WebGLProxy proxy
    *        The proxy methods for the WebGL context owning this shader.
    */
   initialize: function(conn, program, shader, proxy) {
     protocol.Actor.prototype.initialize.call(this, conn);
     this.program = program;
     this.shader = shader;
     this.text = proxy.getShaderSource(shader);
     this.linkedProxy = proxy;
   },
   /**
    * Gets the source code for this shader.
    */
   getText: method(function() {
     return this.text;
   }, {
     response: { text: RetVal("string") }
   }),
   /**
    * Sets and compiles new source code for this shader.
    */
   compile: method(function(text) {
     // Get the shader and corresponding program to change via the WebGL proxy.
     let { linkedProxy: proxy, shader, program } = this;
     // Get the new shader source to inject.
     let oldText = this.text;
     let newText = text;
     // Overwrite the shader's source.
     let error = proxy.compileShader(program, shader, this.text = newText);
     // If something went wrong, revert to the previous shader.
     if (error.compile || error.link) {
       proxy.compileShader(program, shader, this.text = oldText);
       return error;
     }
     return undefined;
   }, {
     request: { text: Arg(0, "string") },
     response: { error: RetVal("nullable:json") }
   })
 });
 /**
  * The corresponding Front object for the ShaderActor.
  */
 let ShaderFront = protocol.FrontClass(ShaderActor, {
   initialize: function(client, form) {
     protocol.Front.prototype.initialize.call(this, client, form);
   }
 });
 /**
  * A WebGL program is composed (at the moment, analogue to OpenGL ES 2.0)
  * of two shaders: a vertex shader and a fragment shader.
  */
 let ProgramActor = protocol.ActorClass({
   typeName: "gl-program",
   /**
    * Create the program actor.
    *
    * @param DebuggerServerConnection conn
    *        The server connection.
    * @param WebGLProgram program
    *        The WebGL program being linked.
    * @param WebGLShader[] shaders
    *        The WebGL program's cooresponding vertex and fragment shaders.
    * @param WebGLCache cache
    *        The state storage for the WebGL context owning this program.
    * @param WebGLProxy proxy
    *        The proxy methods for the WebGL context owning this program.
    */
   initialize: function(conn, [program, shaders, cache, proxy]) {
     protocol.Actor.prototype.initialize.call(this, conn);
     this._shaderActorsCache = { vertex: null, fragment: null };
     this.program = program;
     this.shaders = shaders;
     this.linkedCache = cache;
     this.linkedProxy = proxy;
   },
   get ownerWindow() this.linkedCache.ownerWindow,
   get ownerContext() this.linkedCache.ownerContext,
   /**
    * Gets the vertex shader linked to this program. This method guarantees
    * a single actor instance per shader.
    */
   getVertexShader: method(function() {
     return this._getShaderActor("vertex");
   }, {
     response: { shader: RetVal("gl-shader") }
   }),
   /**
    * Gets the fragment shader linked to this program. This method guarantees
    * a single actor instance per shader.
    */
   getFragmentShader: method(function() {
     return this._getShaderActor("fragment");
   }, {
     response: { shader: RetVal("gl-shader") }
   }),
   /**
    * Highlights any geometry rendered using this program.
    */
   highlight: method(function(tint) {
     this.linkedProxy.highlightTint = tint;
     this.linkedCache.setProgramTrait(this.program, PROGRAM_HIGHLIGHT_TRAIT);
   }, {
     request: { tint: Arg(0, "array:number") },
     oneway: true
   }),
   /**
    * Allows geometry to be rendered normally using this program.
    */
   unhighlight: method(function() {
     this.linkedCache.unsetProgramTrait(this.program, PROGRAM_HIGHLIGHT_TRAIT);
   }, {
     oneway: true
   }),
   /**
    * Prevents any geometry from being rendered using this program.
    */
   blackbox: method(function() {
     this.linkedCache.setProgramTrait(this.program, PROGRAM_BLACKBOX_TRAIT);
   }, {
     oneway: true
   }),
   /**
    * Allows geometry to be rendered using this program.
    */
   unblackbox: method(function() {
     this.linkedCache.unsetProgramTrait(this.program, PROGRAM_BLACKBOX_TRAIT);
   }, {
     oneway: true
   }),
   /**
    * Returns a cached ShaderActor instance based on the required shader type.
    *
    * @param string type
    *        Either "vertex" or "fragment".
    * @return ShaderActor
    *         The respective shader actor instance.
    */
   _getShaderActor: function(type) {
     if (this._shaderActorsCache[type]) {
       return this._shaderActorsCache[type];
     }
     let proxy = this.linkedProxy;
     let shader = proxy.getShaderOfType(this.shaders, type);
     let shaderActor = new ShaderActor(this.conn, this.program, shader, proxy);
     return this._shaderActorsCache[type] = shaderActor;
   }
 });
 /**
  * The corresponding Front object for the ProgramActor.
  */
 let ProgramFront = protocol.FrontClass(ProgramActor, {
   initialize: function(client, form) {
     protocol.Front.prototype.initialize.call(this, client, form);
   }
 });
 /**
  * The WebGL Actor handles simple interaction with a WebGL context via a few
  * high-level methods. After instantiating this actor, you'll need to set it
  * up by calling setup().
  */
 let WebGLActor = exports.WebGLActor = protocol.ActorClass({
   typeName: "webgl",
   initialize: function(conn, tabActor) {
     protocol.Actor.prototype.initialize.call(this, conn);
     this.tabActor = tabActor;
     this._onGlobalCreated = this._onGlobalCreated.bind(this);
     this._onGlobalDestroyed = this._onGlobalDestroyed.bind(this);
     this._onProgramLinked = this._onProgramLinked.bind(this);
   },
   destroy: function(conn) {
     protocol.Actor.prototype.destroy.call(this, conn);
     this.finalize();
   },
   /**
    * Starts waiting for the current tab actor's document global to be
    * created, in order to instrument the Canvas context and become
    * aware of everything the content does WebGL-wise.
    *
    * See ContentObserver and WebGLInstrumenter for more details.
    */
   setup: method(function({ reload }) {
     if (this._initialized) {
       return;
     }
     this._initialized = true;
     this._programActorsCache = [];
     this._contentObserver = new ContentObserver(this.tabActor);
     this._webglObserver = new WebGLObserver();
     on(this._contentObserver, "global-created", this._onGlobalCreated);
     on(this._contentObserver, "global-destroyed", this._onGlobalDestroyed);
     on(this._webglObserver, "program-linked", this._onProgramLinked);
     if (reload) {
       this.tabActor.window.location.reload();
     }
   }, {
     request: { reload: Option(0, "boolean") },
     oneway: true
   }),
   /**
    * Stops listening for document global changes and puts this actor
    * to hibernation. This method is called automatically just before the
    * actor is destroyed.
    */
   finalize: method(function() {
     if (!this._initialized) {
       return;
     }
     this._initialized = false;
     this._contentObserver.stopListening();
     off(this._contentObserver, "global-created", this._onGlobalCreated);
     off(this._contentObserver, "global-destroyed", this._onGlobalDestroyed);
     off(this._webglObserver, "program-linked", this._onProgramLinked);
     this._programActorsCache = null;
     this._contentObserver = null;
     this._webglObserver = null;
   }, {
    oneway: true
   }),
   /**
    * Gets an array of cached program actors for the current tab actor's window.
    * This is useful for dealing with bfcache, when no new programs are linked.
    */
   getPrograms: method(function() {
     let id = ContentObserver.GetInnerWindowID(this.tabActor.window);
     return this._programActorsCache.filter(e => e.ownerWindow == id);
   }, {
     response: { programs: RetVal("array:gl-program") }
   }),
   /**
    * Events emitted by this actor. The "program-linked" event is fired
    * every time a WebGL program was linked with its respective two shaders.
    */
   events: {
     "program-linked": {
       type: "programLinked",
       program: Arg(0, "gl-program")
     }
   },
   /**
    * Invoked whenever the current tab actor's document global is created.
    */
   _onGlobalCreated: function(window) {
     WebGLInstrumenter.handle(window, this._webglObserver);
   },
   /**
    * Invoked whenever the current tab actor's inner window is destroyed.
    */
   _onGlobalDestroyed: function(id) {
     removeFromArray(this._programActorsCache, e => e.ownerWindow == id);
     this._webglObserver.unregisterContextsForWindow(id);
   },
   /**
    * Invoked whenever an observed WebGL context links a program.
    */
   _onProgramLinked: function(...args) {
     let programActor = new ProgramActor(this.conn, args);
     this._programActorsCache.push(programActor);
     events.emit(this, "program-linked", programActor);
   }
 });
 /**
  * The corresponding Front object for the WebGLActor.
  */
 let WebGLFront = exports.WebGLFront = protocol.FrontClass(WebGLActor, {
   initialize: function(client, { webglActor }) {
     protocol.Front.prototype.initialize.call(this, client, { actor: webglActor });
     client.addActorPool(this);
     this.manage(this);
   }
 });
 /**
  * Instruments a HTMLCanvasElement with the appropriate inspection methods.
  */
 let WebGLInstrumenter = {
   /**
    * Overrides the getContext method in the HTMLCanvasElement prototype.
    *
    * @param nsIDOMWindow window
    *        The window to perform the instrumentation in.
    * @param WebGLObserver observer
    *        The observer watching function calls in the context.
    */
   handle: function(window, observer) {
     let self = this;
     let id = ContentObserver.GetInnerWindowID(window);
     let canvasElem = XPCNativeWrapper.unwrap(window.HTMLCanvasElement);
     let canvasPrototype = canvasElem.prototype;
     let originalGetContext = canvasPrototype.getContext;
     /**
      * Returns a drawing context on the canvas, or null if the context ID is
      * not supported. This override creates an observer for the targeted context
      * type and instruments specific functions in the targeted context instance.
      */
     canvasPrototype.getContext = function(name, options) {
       // Make sure a context was able to be created.
       let context = originalGetContext.call(this, name, options);
       if (!context) {
         return context;
       }
       // Make sure a WebGL (not a 2D) context will be instrumented.
       if (WEBGL_CONTEXT_NAMES.indexOf(name) == -1) {
         return context;
       }
       // Repeated calls to 'getContext' return the same instance, no need to
       // instrument everything again.
       if (observer.for(context)) {
         return context;
       }
       // Create a separate state storage for this context.
       observer.registerContextForWindow(id, context);
       // Link our observer to the new WebGL context methods.
       for (let { timing, callback, functions } of self._methods) {
         for (let func of functions) {
           self._instrument(observer, context, func, callback, timing);
         }
       }
       // Return the decorated context back to the content consumer, which
       // will continue using it normally.
       return context;
     };
   },
   /**
    * Overrides a specific method in a HTMLCanvasElement context.
    *
    * @param WebGLObserver observer
    *        The observer watching function calls in the context.
    * @param WebGLRenderingContext context
    *        The targeted WebGL context instance.
    * @param string funcName
    *        The function to override.
    * @param array callbackName [optional]
    *        The two callback function names in the observer, corresponding to
    *        the "before" and "after" invocation times. If unspecified, they will
    *        default to the name of the function to override.
    * @param number timing [optional]
    *        When to issue the callback in relation to the actual context
    *        function call. Availalble values are -1 for "before" (default)
    *        1 for "after" and 0 for "before and after".
    */
   _instrument: function(observer, context, funcName, callbackName = [], timing = -1) {
     let { cache, proxy } = observer.for(context);
     let originalFunc = context[funcName];
     let beforeFuncName = callbackName[0] || funcName;
     let afterFuncName = callbackName[1] || callbackName[0] || funcName;
     context[funcName] = function(...glArgs) {
       if (timing <= 0 && !observer.suppressHandlers) {
         let glBreak = observer[beforeFuncName](glArgs, cache, proxy);
         if (glBreak) return undefined;
       }
       let glResult = originalFunc.apply(this, glArgs);
       if (timing >= 0 && !observer.suppressHandlers) {
         let glBreak = observer[afterFuncName](glArgs, glResult, cache, proxy);
         if (glBreak) return undefined;
       }
       return glResult;
     };
   },
   /**
    * Override mappings for WebGL methods.
    */
   _methods: [{
     timing: 1, // after
     functions: [
       "linkProgram", "getAttribLocation", "getUniformLocation"
     ]
   }, {
     timing: -1, // before
     callback: [
       "toggleVertexAttribArray"
     ],
     functions: [
       "enableVertexAttribArray", "disableVertexAttribArray"
     ]
   }, {
     timing: -1, // before
     callback: [
       "attribute_"
     ],
     functions: [
       "vertexAttrib1f", "vertexAttrib2f", "vertexAttrib3f", "vertexAttrib4f",
       "vertexAttrib1fv", "vertexAttrib2fv", "vertexAttrib3fv", "vertexAttrib4fv",
       "vertexAttribPointer"
     ]
   }, {
     timing: -1, // before
     callback: [
       "uniform_"
     ],
     functions: [
       "uniform1i", "uniform2i", "uniform3i", "uniform4i",
       "uniform1f", "uniform2f", "uniform3f", "uniform4f",
       "uniform1iv", "uniform2iv", "uniform3iv", "uniform4iv",
       "uniform1fv", "uniform2fv", "uniform3fv", "uniform4fv",
       "uniformMatrix2fv", "uniformMatrix3fv", "uniformMatrix4fv"
     ]
   }, {
     timing: -1, // before
     functions: [
       "useProgram", "enable", "disable", "blendColor",
       "blendEquation", "blendEquationSeparate",
       "blendFunc", "blendFuncSeparate"
     ]
   }, {
     timing: 0, // before and after
     callback: [
       "beforeDraw_", "afterDraw_"
     ],
     functions: [
       "drawArrays", "drawElements"
     ]
   }]
   // TODO: It'd be a good idea to handle other functions as well:
   //   - getActiveUniform
   //   - getUniform
   //   - getActiveAttrib
   //   - getVertexAttrib
 };
 /**
  * An observer that captures a WebGL context's method calls.
  */
 function WebGLObserver() {
   this._contexts = new Map();
 }
 WebGLObserver.prototype = {
   _contexts: null,
   /**
    * Creates a WebGLCache and a WebGLProxy for the specified window and context.
    *
    * @param number id
    *        The id of the window containing the WebGL context.
    * @param WebGLRenderingContext context
    *        The WebGL context used in the cache and proxy instances.
    */
   registerContextForWindow: function(id, context) {
     let cache = new WebGLCache(id, context);
     let proxy = new WebGLProxy(id, context, cache, this);
     cache.refreshState(proxy);
     this._contexts.set(context, {
       ownerWindow: id,
       cache: cache,
       proxy: proxy
     });
   },
   /**
    * Removes all WebGLCache and WebGLProxy instances for a particular window.
    *
    * @param number id
    *        The id of the window containing the WebGL context.
    */
   unregisterContextsForWindow: function(id) {
     removeFromMap(this._contexts, e => e.ownerWindow == id);
   },
   /**
    * Gets the WebGLCache and WebGLProxy instances for a particular context.
    *
    * @param WebGLRenderingContext context
    *        The WebGL context used in the cache and proxy instances.
    * @return object
    *         An object containing the corresponding { cache, proxy } instances.
    */
   for: function(context) {
     return this._contexts.get(context);
   },
   /**
    * Set this flag to true to stop observing any context function calls.
    */
   suppressHandlers: false,
   /**
    * Called immediately *after* 'linkProgram' is requested in the context.
    *
    * @param array glArgs
    *        Overridable arguments with which the function is called.
    * @param void glResult
    *        The returned value of the original function call.
    * @param WebGLCache cache
    *        The state storage for the WebGL context initiating this call.
    * @param WebGLProxy proxy
    *        The proxy methods for the WebGL context initiating this call.
    */
   linkProgram: function(glArgs, glResult, cache, proxy) {
     let program = glArgs[0];
     let shaders = proxy.getAttachedShaders(program);
     cache.addProgram(program, PROGRAM_DEFAULT_TRAITS);
     emit(this, "program-linked", program, shaders, cache, proxy);
   },
   /**
    * Called immediately *after* 'getAttribLocation' is requested in the context.
    *
    * @param array glArgs
    *        Overridable arguments with which the function is called.
    * @param GLint glResult
    *        The returned value of the original function call.
    * @param WebGLCache cache
    *        The state storage for the WebGL context initiating this call.
    */
   getAttribLocation: function(glArgs, glResult, cache) {
     // Make sure the attribute's value is legal before caching.
     if (glResult < 0) {
       return;
     }
     let [program, name] = glArgs;
     cache.addAttribute(program, name, glResult);
   },
   /**
    * Called immediately *after* 'getUniformLocation' is requested in the context.
    *
    * @param array glArgs
    *        Overridable arguments with which the function is called.
    * @param WebGLUniformLocation glResult
    *        The returned value of the original function call.
    * @param WebGLCache cache
    *        The state storage for the WebGL context initiating this call.
    */
   getUniformLocation: function(glArgs, glResult, cache) {
     // Make sure the uniform's value is legal before caching.
     if (!glResult) {
       return;
     }
     let [program, name] = glArgs;
     cache.addUniform(program, name, glResult);
   },
   /**
    * Called immediately *before* 'enableVertexAttribArray' or
    * 'disableVertexAttribArray'is requested in the context.
    *
    * @param array glArgs
    *        Overridable arguments with which the function is called.
    * @param WebGLCache cache
    *        The state storage for the WebGL context initiating this call.
    */
   toggleVertexAttribArray: function(glArgs, cache) {
     glArgs[0] = cache.getCurrentAttributeLocation(glArgs[0]);
     return glArgs[0] < 0; // Return true to break original function call.
   },
   /**
    * Called immediately *before* 'attribute_' is requested in the context.
    *
    * @param array glArgs
    *        Overridable arguments with which the function is called.
    * @param WebGLCache cache
    *        The state storage for the WebGL context initiating this call.
    */
   attribute_: function(glArgs, cache) {
     glArgs[0] = cache.getCurrentAttributeLocation(glArgs[0]);
     return glArgs[0] < 0; // Return true to break original function call.
   },
   /**
    * Called immediately *before* 'uniform_' is requested in the context.
    *
    * @param array glArgs
    *        Overridable arguments with which the function is called.
    * @param WebGLCache cache
    *        The state storage for the WebGL context initiating this call.
    */
   uniform_: function(glArgs, cache) {
     glArgs[0] = cache.getCurrentUniformLocation(glArgs[0]);
     return !glArgs[0]; // Return true to break original function call.
   },
   /**
    * Called immediately *before* 'useProgram' is requested in the context.
    *
    * @param array glArgs
    *        Overridable arguments with which the function is called.
    * @param WebGLCache cache
    *        The state storage for the WebGL context initiating this call.
    */
   useProgram: function(glArgs, cache) {
     // Manually keeping a cache and not using gl.getParameter(CURRENT_PROGRAM)
     // because gl.get* functions are slow as potatoes.
     cache.currentProgram = glArgs[0];
   },
   /**
    * Called immediately *before* 'enable' is requested in the context.
    *
    * @param array glArgs
    *        Overridable arguments with which the function is called.
    * @param WebGLCache cache
    *        The state storage for the WebGL context initiating this call.
    */
   enable: function(glArgs, cache) {
     cache.currentState[glArgs[0]] = true;
   },
   /**
    * Called immediately *before* 'disable' is requested in the context.
    *
    * @param array glArgs
    *        Overridable arguments with which the function is called.
    * @param WebGLCache cache
    *        The state storage for the WebGL context initiating this call.
    */
   disable: function(glArgs, cache) {
     cache.currentState[glArgs[0]] = false;
   },
   /**
    * Called immediately *before* 'blendColor' is requested in the context.
    *
    * @param array glArgs
    *        Overridable arguments with which the function is called.
    * @param WebGLCache cache
    *        The state storage for the WebGL context initiating this call.
    */
   blendColor: function(glArgs, cache) {
     let blendColor = cache.currentState.blendColor;
     blendColor[0] = glArgs[0];
     blendColor[1] = glArgs[1];
     blendColor[2] = glArgs[2];
     blendColor[3] = glArgs[3];
   },
   /**
    * Called immediately *before* 'blendEquation' is requested in the context.
    *
    * @param array glArgs
    *        Overridable arguments with which the function is called.
    * @param WebGLCache cache
    *        The state storage for the WebGL context initiating this call.
    */
   blendEquation: function(glArgs, cache) {
     let state = cache.currentState;
     state.blendEquationRgb = state.blendEquationAlpha = glArgs[0];
   },
   /**
    * Called immediately *before* 'blendEquationSeparate' is requested in the context.
    *
    * @param array glArgs
    *        Overridable arguments with which the function is called.
    * @param WebGLCache cache
    *        The state storage for the WebGL context initiating this call.
    */
   blendEquationSeparate: function(glArgs, cache) {
     let state = cache.currentState;
     state.blendEquationRgb = glArgs[0];
     state.blendEquationAlpha = glArgs[1];
   },
   /**
    * Called immediately *before* 'blendFunc' is requested in the context.
    *
    * @param array glArgs
    *        Overridable arguments with which the function is called.
    * @param WebGLCache cache
    *        The state storage for the WebGL context initiating this call.
    */
   blendFunc: function(glArgs, cache) {
     let state = cache.currentState;
     state.blendSrcRgb = state.blendSrcAlpha = glArgs[0];
     state.blendDstRgb = state.blendDstAlpha = glArgs[1];
   },
   /**
    * Called immediately *before* 'blendFuncSeparate' is requested in the context.
    *
    * @param array glArgs
    *        Overridable arguments with which the function is called.
    * @param WebGLCache cache
    *        The state storage for the WebGL context initiating this call.
    */
   blendFuncSeparate: function(glArgs, cache) {
     let state = cache.currentState;
     state.blendSrcRgb = glArgs[0];
     state.blendDstRgb = glArgs[1];
     state.blendSrcAlpha = glArgs[2];
     state.blendDstAlpha = glArgs[3];
   },
   /**
    * Called immediately *before* 'drawArrays' or 'drawElements' is requested
    * in the context.
    *
    * @param array glArgs
    *        Overridable arguments with which the function is called.
    * @param WebGLCache cache
    *        The state storage for the WebGL context initiating this call.
    * @param WebGLProxy proxy
    *        The proxy methods for the WebGL context initiating this call.
    */
   beforeDraw_: function(glArgs, cache, proxy) {
     let traits = cache.currentProgramTraits;
     // Handle program blackboxing.
     if (traits & PROGRAM_BLACKBOX_TRAIT) {
       return true; // Return true to break original function call.
     }
     // Handle program highlighting.
     if (traits & PROGRAM_HIGHLIGHT_TRAIT) {
       proxy.enableHighlighting();
     }
     return false;
   },
   /**
    * Called immediately *after* 'drawArrays' or 'drawElements' is requested
    * in the context.
    *
    * @param array glArgs
    *        Overridable arguments with which the function is called.
    * @param void glResult
    *        The returned value of the original function call.
    * @param WebGLCache cache
    *        The state storage for the WebGL context initiating this call.
    * @param WebGLProxy proxy
    *        The proxy methods for the WebGL context initiating this call.
    */
   afterDraw_: function(glArgs, glResult, cache, proxy) {
     let traits = cache.currentProgramTraits;
     // Handle program highlighting.
     if (traits & PROGRAM_HIGHLIGHT_TRAIT) {
       proxy.disableHighlighting();
     }
   }
 };
 /**
  * A mechanism for storing a single WebGL context's state, programs, shaders,
  * attributes or uniforms.
  *
  * @param number id
  *        The id of the window containing the WebGL context.
  * @param WebGLRenderingContext context
  *        The WebGL context for which the state is stored.
  */
 function WebGLCache(id, context) {
   this._id = id;
   this._gl = context;
   this._programs = new Map();
   this.currentState = {};
 }
 WebGLCache.prototype = {
   _id: 0,
   _gl: null,
   _programs: null,
   _currentProgramInfo: null,
   _currentAttributesMap: null,
   _currentUniformsMap: null,
   get ownerWindow() this._id,
   get ownerContext() this._gl,
   /**
    * A collection of flags or properties representing the context's state.
    * Implemented as an object hash and not a Map instance because keys are
    * always either strings or numbers.
    */
   currentState: null,
   /**
    * Populates the current state with values retrieved from the context.
    *
    * @param WebGLProxy proxy
    *        The proxy methods for the WebGL context owning the state.
    */
   refreshState: function(proxy) {
     let gl = this._gl;
     let s = this.currentState;
     // Populate only with the necessary parameters. Not all default WebGL
     // state values are required.
     s[gl.BLEND] = proxy.isEnabled("BLEND");
     s.blendColor = proxy.getParameter("BLEND_COLOR");
     s.blendEquationRgb = proxy.getParameter("BLEND_EQUATION_RGB");
     s.blendEquationAlpha = proxy.getParameter("BLEND_EQUATION_ALPHA");
     s.blendSrcRgb = proxy.getParameter("BLEND_SRC_RGB");
     s.blendSrcAlpha = proxy.getParameter("BLEND_SRC_ALPHA");
     s.blendDstRgb = proxy.getParameter("BLEND_DST_RGB");
     s.blendDstAlpha = proxy.getParameter("BLEND_DST_ALPHA");
   },
   /**
    * Adds a program to the cache.
    *
    * @param WebGLProgram program
    *        The shader for which the traits are to be cached.
    * @param number traits
    *        A default properties mask set for the program.
    */
   addProgram: function(program, traits) {
     this._programs.set(program, {
       traits: traits,
       attributes: [], // keys are GLints (numbers)
       uniforms: new Map() // keys are WebGLUniformLocations (objects)
     });
   },
   /**
    * Adds a specific trait to a program. The effect of such properties is
    * determined by the consumer of this cache.
    *
    * @param WebGLProgram program
    *        The program to add the trait to.
    * @param number trait
    *        The property added to the program.
    */
   setProgramTrait: function(program, trait) {
     this._programs.get(program).traits |= trait;
   },
   /**
    * Removes a specific trait from a program.
    *
    * @param WebGLProgram program
    *        The program to remove the trait from.
    * @param number trait
    *        The property removed from the program.
    */
   unsetProgramTrait: function(program, trait) {
     this._programs.get(program).traits &= ~trait;
   },
   /**
    * Sets the currently used program in the context.
    * @param WebGLProgram program
    */
   set currentProgram(program) {
     let programInfo = this._programs.get(program);
     if (programInfo == null) {
       return;
     }
     this._currentProgramInfo = programInfo;
     this._currentAttributesMap = programInfo.attributes;
     this._currentUniformsMap = programInfo.uniforms;
   },
   /**
    * Gets the traits for the currently used program.
    * @return number
    */
   get currentProgramTraits() {
     return this._currentProgramInfo.traits;
   },
   /**
    * Adds an attribute to the cache.
    *
    * @param WebGLProgram program
    *        The program for which the attribute is bound.
    * @param string name
    *        The attribute name.
    * @param GLint value
    *        The attribute value.
    */
   addAttribute: function(program, name, value) {
     this._programs.get(program).attributes[value] = {
       name: name,
       value: value
     };
   },
   /**
    * Adds a uniform to the cache.
    *
    * @param WebGLProgram program
    *        The program for which the uniform is bound.
    * @param string name
    *        The uniform name.
    * @param WebGLUniformLocation value
    *        The uniform value.
    */
   addUniform: function(program, name, value) {
     this._programs.get(program).uniforms.set(new XPCNativeWrapper(value), {
       name: name,
       value: value
     });
   },
   /**
    * Updates the attribute locations for a specific program.
    * This is necessary, for example, when the shader is relinked and all the
    * attribute locations become obsolete.
    *
    * @param WebGLProgram program
    *        The program for which the attributes need updating.
    */
   updateAttributesForProgram: function(program) {
     let attributes = this._programs.get(program).attributes;
     for (let attribute of attributes) {
       attribute.value = this._gl.getAttribLocation(program, attribute.name);
     }
   },
   /**
    * Updates the uniform locations for a specific program.
    * This is necessary, for example, when the shader is relinked and all the
    * uniform locations become obsolete.
    *
    * @param WebGLProgram program
    *        The program for which the uniforms need updating.
    */
   updateUniformsForProgram: function(program) {
     let uniforms = this._programs.get(program).uniforms;
     for (let [, uniform] of uniforms) {
       uniform.value = this._gl.getUniformLocation(program, uniform.name);
     }
   },
   /**
    * Gets the actual attribute location in a specific program.
    * When relinked, all the attribute locations become obsolete and are updated
    * in the cache. This method returns the (current) real attribute location.
    *
    * @param GLint initialValue
    *        The initial attribute value.
    * @return GLint
    *         The current attribute value, or the initial value if it's already
    *         up to date with its corresponding program.
    */
   getCurrentAttributeLocation: function(initialValue) {
     let attributes = this._currentAttributesMap;
     let currentInfo = attributes ? attributes[initialValue] : null;
     return currentInfo ? currentInfo.value : initialValue;
   },
   /**
    * Gets the actual uniform location in a specific program.
    * When relinked, all the uniform locations become obsolete and are updated
    * in the cache. This method returns the (current) real uniform location.
    *
    * @param WebGLUniformLocation initialValue
    *        The initial uniform value.
    * @return WebGLUniformLocation
    *         The current uniform value, or the initial value if it's already
    *         up to date with its corresponding program.
    */
   getCurrentUniformLocation: function(initialValue) {
     let uniforms = this._currentUniformsMap;
     let currentInfo = uniforms ? uniforms.get(initialValue) : null;
     return currentInfo ? currentInfo.value : initialValue;
   }
 };
 /**
  * A mechanism for injecting or qureying state into/from a single WebGL context.
  *
  * Any interaction with a WebGL context should go through this proxy.
  * Otherwise, the corresponding observer would register the calls as coming
  * from content, which is usually not desirable. Infinite call stacks are bad.
  *
  * @param number id
  *        The id of the window containing the WebGL context.
  * @param WebGLRenderingContext context
  *        The WebGL context used for the proxy methods.
  * @param WebGLCache cache
  *        The state storage for the corresponding context.
  * @param WebGLObserver observer
  *        The observer watching function calls in the corresponding context.
  */
 function WebGLProxy(id, context, cache, observer) {
   this._id = id;
   this._gl = context;
   this._cache = cache;
   this._observer = observer;
   let exports = [
     "isEnabled",
     "getParameter",
     "getAttachedShaders",
     "getShaderSource",
     "getShaderOfType",
     "compileShader",
     "enableHighlighting",
     "disableHighlighting"
   ];
   exports.forEach(e => this[e] = (...args) => this._call(e, args));
 }
 WebGLProxy.prototype = {
   _id: 0,
   _gl: null,
   _cache: null,
   _observer: null,
   get ownerWindow() this._id,
   get ownerContext() this._gl,
   /**
    * Test whether a WebGL capability is enabled.
    *
    * @param string name
    *        The WebGL capability name, for example "BLEND".
    * @return boolean
    *         True if enabled, false otherwise.
    */
   _isEnabled: function(name) {
     return this._gl.isEnabled(this._gl[name]);
   },
   /**
    * Returns the value for the specified WebGL parameter name.
    *
    * @param string name
    *        The WebGL parameter name, for example "BLEND_COLOR".
    * @return any
    *         The corresponding parameter's value.
    */
   _getParameter: function(name) {
     return this._gl.getParameter(this._gl[name]);
   },
   /**
    * Returns the renderbuffer property value for the specified WebGL parameter.
    * If no renderbuffer binding is available, null is returned.
    *
    * @param string name
    *        The WebGL parameter name, for example "BLEND_COLOR".
    * @return any
    *         The corresponding parameter's value.
    */
   _getRenderbufferParameter: function(name) {
     if (!this._getParameter("RENDERBUFFER_BINDING")) {
       return null;
     }
     let gl = this._gl;
     return gl.getRenderbufferParameter(gl.RENDERBUFFER, gl[name]);
   },
   /**
    * Returns the framebuffer property value for the specified WebGL parameter.
    * If no framebuffer binding is available, null is returned.
    *
    * @param string type
    *        The framebuffer object attachment point, for example "COLOR_ATTACHMENT0".
    * @param string name
    *        The WebGL parameter name, for example "FRAMEBUFFER_ATTACHMENT_OBJECT_NAME".
    *        If unspecified, defaults to "FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE".
    * @return any
    *         The corresponding parameter's value.
    */
   _getFramebufferAttachmentParameter: function(type, name = "FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE") {
     if (!this._getParameter("FRAMEBUFFER_BINDING")) {
       return null;
     }
     let gl = this._gl;
     return gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl[type], gl[name]);
   },
   /**
    * Returns the shader objects attached to a program object.
    *
    * @param WebGLProgram program
    *        The program for which to retrieve the attached shaders.
    * @return array
    *         The attached vertex and fragment shaders.
    */
   _getAttachedShaders: function(program) {
     return this._gl.getAttachedShaders(program);
   },
   /**
    * Returns the source code string from a shader object.
    *
    * @param WebGLShader shader
    *        The shader for which to retrieve the source code.
    * @return string
    *         The shader's source code.
    */
   _getShaderSource: function(shader) {
     return this._gl.getShaderSource(shader);
   },
   /**
    * Finds a shader of the specified type in a list.
    *
    * @param WebGLShader[] shaders
    *        The shaders for which to check the type.
    * @param string type
    *        Either "vertex" or "fragment".
    * @return WebGLShader | null
    *         The shader of the specified type, or null if nothing is found.
    */
   _getShaderOfType: function(shaders, type) {
     let gl = this._gl;
     let shaderTypeEnum = {
       vertex: gl.VERTEX_SHADER,
       fragment: gl.FRAGMENT_SHADER
     }[type];
     for (let shader of shaders) {
       if (gl.getShaderParameter(shader, gl.SHADER_TYPE) == shaderTypeEnum) {
         return shader;
       }
     }
     return null;
   },
   /**
    * Changes a shader's source code and relinks the respective program.
    *
    * @param WebGLProgram program
    *        The program who's linked shader is to be modified.
    * @param WebGLShader shader
    *        The shader to be modified.
    * @param string text
    *        The new shader source code.
    * @return object
    *         An object containing the compilation and linking status.
    */
   _compileShader: function(program, shader, text) {
     let gl = this._gl;
     gl.shaderSource(shader, text);
     gl.compileShader(shader);
     gl.linkProgram(program);
     let error = { compile: "", link: "" };
     if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
       error.compile = gl.getShaderInfoLog(shader);
     }
     if (!gl.getProgramParameter(program, gl.LINK_STATUS)) {
       error.link = gl.getShaderInfoLog(shader);
     }
     this._cache.updateAttributesForProgram(program);
     this._cache.updateUniformsForProgram(program);
     return error;
   },
   /**
    * Enables color blending based on the geometry highlight tint.
    */
   _enableHighlighting: function() {
     let gl = this._gl;
     // Avoid changing the blending params when "rendering to texture".
     // Check drawing to a custom framebuffer bound to the default renderbuffer.
     let hasFramebuffer = this._getParameter("FRAMEBUFFER_BINDING");
     let hasRenderbuffer = this._getParameter("RENDERBUFFER_BINDING");
     if (hasFramebuffer && !hasRenderbuffer) {
       return;
     }
     // Check drawing to a depth or stencil component of the framebuffer.
     let writesDepth = this._getFramebufferAttachmentParameter("DEPTH_ATTACHMENT");
     let writesStencil = this._getFramebufferAttachmentParameter("STENCIL_ATTACHMENT");
     if (writesDepth || writesStencil) {
       return;
     }
     // Non-premultiplied alpha blending based on a predefined constant color.
     // Simply using gl.colorMask won't work, because we want non-tinted colors
     // to be drawn as black, not ignored.
     gl.enable(gl.BLEND);
     gl.blendColor.apply(gl, this.highlightTint);
     gl.blendEquation(gl.FUNC_ADD);
     gl.blendFunc(gl.CONSTANT_COLOR, gl.ONE_MINUS_SRC_ALPHA, gl.CONSTANT_COLOR, gl.ZERO);
     this.wasHighlighting = true;
   },
   /**
    * Disables color blending based on the geometry highlight tint, by
    * reverting the corresponding params back to their original values.
    */
   _disableHighlighting: function() {
     let gl = this._gl;
     let s = this._cache.currentState;
     gl[s[gl.BLEND] ? "enable" : "disable"](gl.BLEND);
     gl.blendColor.apply(gl, s.blendColor);
     gl.blendEquationSeparate(s.blendEquationRgb, s.blendEquationAlpha);
     gl.blendFuncSeparate(s.blendSrcRgb, s.blendDstRgb, s.blendSrcAlpha, s.blendDstAlpha);
   },
   /**
    * The color tint used for highlighting geometry.
    * @see _enableHighlighting and _disableHighlighting.
    */
   highlightTint: [0, 0, 0, 0],
   /**
    * Executes a function in this object.
    *
    * This method makes sure that any handlers in the context observer are
    * suppressed, hence stopping observing any context function calls.
    *
    * @param string funcName
    *        The function to call.
    * @param array args
    *        An array of arguments.
    * @return any
    *         The called function result.
    */
   _call: function(funcName, args) {
     let prevState = this._observer.suppressHandlers;
     this._observer.suppressHandlers = true;
     let result = this["_" + funcName].apply(this, args);
     this._observer.suppressHandlers = prevState;
     return result;
   }
 };
 // Utility functions.
 function removeFromMap(map, predicate) {
   for (let [key, value] of map) {
     if (predicate(value)) {
       map.delete(key);
     }
   }
 };
 function removeFromArray(array, predicate) {
   for (let value of array) {
     if (predicate(value)) {
       array.splice(array.indexOf(value), 1);
     }
   }
 }