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authorMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
committerMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
commit5f8de423f190bbb79a62f804151bc24824fa32d8 (patch)
tree10027f336435511475e392454359edea8e25895d /devtools/server/actors/canvas.js
parent49ee0794b5d912db1f95dce6eb52d781dc210db5 (diff)
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+/* 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 promise = require("promise");
+const protocol = require("devtools/shared/protocol");
+const {CallWatcherActor} = require("devtools/server/actors/call-watcher");
+const {CallWatcherFront} = require("devtools/shared/fronts/call-watcher");
+const DevToolsUtils = require("devtools/shared/DevToolsUtils");
+const {WebGLPrimitiveCounter} = require("devtools/server/primitive");
+const {
+ frameSnapshotSpec,
+ canvasSpec,
+ CANVAS_CONTEXTS,
+ ANIMATION_GENERATORS,
+ LOOP_GENERATORS,
+ DRAW_CALLS,
+ INTERESTING_CALLS,
+} = require("devtools/shared/specs/canvas");
+const {CanvasFront} = require("devtools/shared/fronts/canvas");
+
+const {on, once, off, emit} = events;
+const {method, custom, Arg, Option, RetVal} = protocol;
+
+/**
+ * This actor represents a recorded animation frame snapshot, along with
+ * all the corresponding canvas' context methods invoked in that frame,
+ * thumbnails for each draw call and a screenshot of the end result.
+ */
+var FrameSnapshotActor = protocol.ActorClassWithSpec(frameSnapshotSpec, {
+ /**
+ * Creates the frame snapshot call actor.
+ *
+ * @param DebuggerServerConnection conn
+ * The server connection.
+ * @param HTMLCanvasElement canvas
+ * A reference to the content canvas.
+ * @param array calls
+ * An array of "function-call" actor instances.
+ * @param object screenshot
+ * A single "snapshot-image" type instance.
+ */
+ initialize: function (conn, { canvas, calls, screenshot, primitive }) {
+ protocol.Actor.prototype.initialize.call(this, conn);
+ this._contentCanvas = canvas;
+ this._functionCalls = calls;
+ this._animationFrameEndScreenshot = screenshot;
+ this._primitive = primitive;
+ },
+
+ /**
+ * Gets as much data about this snapshot without computing anything costly.
+ */
+ getOverview: function () {
+ return {
+ calls: this._functionCalls,
+ thumbnails: this._functionCalls.map(e => e._thumbnail).filter(e => !!e),
+ screenshot: this._animationFrameEndScreenshot,
+ primitive: {
+ tris: this._primitive.tris,
+ vertices: this._primitive.vertices,
+ points: this._primitive.points,
+ lines: this._primitive.lines
+ }
+ };
+ },
+
+ /**
+ * Gets a screenshot of the canvas's contents after the specified
+ * function was called.
+ */
+ generateScreenshotFor: function (functionCall) {
+ let caller = functionCall.details.caller;
+ let global = functionCall.details.global;
+
+ let canvas = this._contentCanvas;
+ let calls = this._functionCalls;
+ let index = calls.indexOf(functionCall);
+
+ // To get a screenshot, replay all the steps necessary to render the frame,
+ // by invoking the context calls up to and including the specified one.
+ // This will be done in a custom framebuffer in case of a WebGL context.
+ let replayData = ContextUtils.replayAnimationFrame({
+ contextType: global,
+ canvas: canvas,
+ calls: calls,
+ first: 0,
+ last: index
+ });
+
+ let { replayContext, replayContextScaling, lastDrawCallIndex, doCleanup } = replayData;
+ let [left, top, width, height] = replayData.replayViewport;
+ let screenshot;
+
+ // Depending on the canvas' context, generating a screenshot is done
+ // in different ways.
+ if (global == "WebGLRenderingContext") {
+ screenshot = ContextUtils.getPixelsForWebGL(replayContext, left, top, width, height);
+ screenshot.flipped = true;
+ } else if (global == "CanvasRenderingContext2D") {
+ screenshot = ContextUtils.getPixelsFor2D(replayContext, left, top, width, height);
+ screenshot.flipped = false;
+ }
+
+ // In case of the WebGL context, we also need to reset the framebuffer
+ // binding to the original value, after generating the screenshot.
+ doCleanup();
+
+ screenshot.scaling = replayContextScaling;
+ screenshot.index = lastDrawCallIndex;
+ return screenshot;
+ }
+});
+
+/**
+ * This Canvas Actor handles simple instrumentation of all the methods
+ * of a 2D or WebGL context, to provide information regarding all the calls
+ * made when drawing frame inside an animation loop.
+ */
+var CanvasActor = exports.CanvasActor = protocol.ActorClassWithSpec(canvasSpec, {
+ // Reset for each recording, boolean indicating whether or not
+ // any draw calls were called for a recording.
+ _animationContainsDrawCall: false,
+
+ initialize: function (conn, tabActor) {
+ protocol.Actor.prototype.initialize.call(this, conn);
+ this.tabActor = tabActor;
+ this._webGLPrimitiveCounter = new WebGLPrimitiveCounter(tabActor);
+ this._onContentFunctionCall = this._onContentFunctionCall.bind(this);
+ },
+ destroy: function (conn) {
+ protocol.Actor.prototype.destroy.call(this, conn);
+ this._webGLPrimitiveCounter.destroy();
+ this.finalize();
+ },
+
+ /**
+ * Starts listening for function calls.
+ */
+ setup: function ({ reload }) {
+ if (this._initialized) {
+ if (reload) {
+ this.tabActor.window.location.reload();
+ }
+ return;
+ }
+ this._initialized = true;
+
+ this._callWatcher = new CallWatcherActor(this.conn, this.tabActor);
+ this._callWatcher.onCall = this._onContentFunctionCall;
+ this._callWatcher.setup({
+ tracedGlobals: CANVAS_CONTEXTS,
+ tracedFunctions: [...ANIMATION_GENERATORS, ...LOOP_GENERATORS],
+ performReload: reload,
+ storeCalls: true
+ });
+ },
+
+ /**
+ * Stops listening for function calls.
+ */
+ finalize: function () {
+ if (!this._initialized) {
+ return;
+ }
+ this._initialized = false;
+
+ this._callWatcher.finalize();
+ this._callWatcher = null;
+ },
+
+ /**
+ * Returns whether this actor has been set up.
+ */
+ isInitialized: function () {
+ return !!this._initialized;
+ },
+
+ /**
+ * Returns whether or not the CanvasActor is recording an animation.
+ * Used in tests.
+ */
+ isRecording: function () {
+ return !!this._callWatcher.isRecording();
+ },
+
+ /**
+ * Records a snapshot of all the calls made during the next animation frame.
+ * The animation should be implemented via the de-facto requestAnimationFrame
+ * utility, or inside recursive `setTimeout`s. `setInterval` at this time are not supported.
+ */
+ recordAnimationFrame: function () {
+ if (this._callWatcher.isRecording()) {
+ return this._currentAnimationFrameSnapshot.promise;
+ }
+
+ this._recordingContainsDrawCall = false;
+ this._callWatcher.eraseRecording();
+ this._callWatcher.initTimestampEpoch();
+ this._webGLPrimitiveCounter.resetCounts();
+ this._callWatcher.resumeRecording();
+
+ let deferred = this._currentAnimationFrameSnapshot = promise.defer();
+ return deferred.promise;
+ },
+
+ /**
+ * Cease attempts to record an animation frame.
+ */
+ stopRecordingAnimationFrame: function () {
+ if (!this._callWatcher.isRecording()) {
+ return;
+ }
+ this._animationStarted = false;
+ this._callWatcher.pauseRecording();
+ this._callWatcher.eraseRecording();
+ this._currentAnimationFrameSnapshot.resolve(null);
+ this._currentAnimationFrameSnapshot = null;
+ },
+
+ /**
+ * Invoked whenever an instrumented function is called, be it on a
+ * 2d or WebGL context, or an animation generator like requestAnimationFrame.
+ */
+ _onContentFunctionCall: function (functionCall) {
+ let { window, name, args } = functionCall.details;
+
+ // The function call arguments are required to replay animation frames,
+ // in order to generate screenshots. However, simply storing references to
+ // every kind of object is a bad idea, since their properties may change.
+ // Consider transformation matrices for example, which are typically
+ // Float32Arrays whose values can easily change across context calls.
+ // They need to be cloned.
+ inplaceShallowCloneArrays(args, window);
+
+ // Handle animations generated using requestAnimationFrame
+ if (CanvasFront.ANIMATION_GENERATORS.has(name)) {
+ this._handleAnimationFrame(functionCall);
+ return;
+ }
+ // Handle animations generated using setTimeout. While using
+ // those timers is considered extremely poor practice, they're still widely
+ // used on the web, especially for old demos; it's nice to support them as well.
+ if (CanvasFront.LOOP_GENERATORS.has(name)) {
+ this._handleAnimationFrame(functionCall);
+ return;
+ }
+ if (CanvasFront.DRAW_CALLS.has(name) && this._animationStarted) {
+ this._handleDrawCall(functionCall);
+ this._webGLPrimitiveCounter.handleDrawPrimitive(functionCall);
+ return;
+ }
+ },
+
+ /**
+ * Handle animations generated using requestAnimationFrame.
+ */
+ _handleAnimationFrame: function (functionCall) {
+ if (!this._animationStarted) {
+ this._handleAnimationFrameBegin();
+ }
+ // Check to see if draw calls occurred yet, as it could be future frames,
+ // like in the scenario where requestAnimationFrame is called to trigger an animation,
+ // and rAF is at the beginning of the animate loop.
+ else if (this._animationContainsDrawCall) {
+ this._handleAnimationFrameEnd(functionCall);
+ }
+ },
+
+ /**
+ * Called whenever an animation frame rendering begins.
+ */
+ _handleAnimationFrameBegin: function () {
+ this._callWatcher.eraseRecording();
+ this._animationStarted = true;
+ },
+
+ /**
+ * Called whenever an animation frame rendering ends.
+ */
+ _handleAnimationFrameEnd: function () {
+ // Get a hold of all the function calls made during this animation frame.
+ // Since only one snapshot can be recorded at a time, erase all the
+ // previously recorded calls.
+ let functionCalls = this._callWatcher.pauseRecording();
+ this._callWatcher.eraseRecording();
+ this._animationContainsDrawCall = false;
+
+ // Since the animation frame finished, get a hold of the (already retrieved)
+ // canvas pixels to conveniently create a screenshot of the final rendering.
+ let index = this._lastDrawCallIndex;
+ let width = this._lastContentCanvasWidth;
+ let height = this._lastContentCanvasHeight;
+ let flipped = !!this._lastThumbnailFlipped; // undefined -> false
+ let pixels = ContextUtils.getPixelStorage()["8bit"];
+ let primitiveResult = this._webGLPrimitiveCounter.getCounts();
+ let animationFrameEndScreenshot = {
+ index: index,
+ width: width,
+ height: height,
+ scaling: 1,
+ flipped: flipped,
+ pixels: pixels.subarray(0, width * height * 4)
+ };
+
+ // Wrap the function calls and screenshot in a FrameSnapshotActor instance,
+ // which will resolve the promise returned by `recordAnimationFrame`.
+ let frameSnapshot = new FrameSnapshotActor(this.conn, {
+ canvas: this._lastDrawCallCanvas,
+ calls: functionCalls,
+ screenshot: animationFrameEndScreenshot,
+ primitive: {
+ tris: primitiveResult.tris,
+ vertices: primitiveResult.vertices,
+ points: primitiveResult.points,
+ lines: primitiveResult.lines
+ }
+ });
+
+ this._currentAnimationFrameSnapshot.resolve(frameSnapshot);
+ this._currentAnimationFrameSnapshot = null;
+ this._animationStarted = false;
+ },
+
+ /**
+ * Invoked whenever a draw call is detected in the animation frame which is
+ * currently being recorded.
+ */
+ _handleDrawCall: function (functionCall) {
+ let functionCalls = this._callWatcher.pauseRecording();
+ let caller = functionCall.details.caller;
+ let global = functionCall.details.global;
+
+ let contentCanvas = this._lastDrawCallCanvas = caller.canvas;
+ let index = this._lastDrawCallIndex = functionCalls.indexOf(functionCall);
+ let w = this._lastContentCanvasWidth = contentCanvas.width;
+ let h = this._lastContentCanvasHeight = contentCanvas.height;
+
+ // To keep things fast, generate images of small and fixed dimensions.
+ let dimensions = CanvasFront.THUMBNAIL_SIZE;
+ let thumbnail;
+
+ this._animationContainsDrawCall = true;
+
+ // Create a thumbnail on every draw call on the canvas context, to augment
+ // the respective function call actor with this additional data.
+ if (global == "WebGLRenderingContext") {
+ // Check if drawing to a custom framebuffer (when rendering to texture).
+ // Don't create a thumbnail in this particular case.
+ let framebufferBinding = caller.getParameter(caller.FRAMEBUFFER_BINDING);
+ if (framebufferBinding == null) {
+ thumbnail = ContextUtils.getPixelsForWebGL(caller, 0, 0, w, h, dimensions);
+ thumbnail.flipped = this._lastThumbnailFlipped = true;
+ thumbnail.index = index;
+ }
+ } else if (global == "CanvasRenderingContext2D") {
+ thumbnail = ContextUtils.getPixelsFor2D(caller, 0, 0, w, h, dimensions);
+ thumbnail.flipped = this._lastThumbnailFlipped = false;
+ thumbnail.index = index;
+ }
+
+ functionCall._thumbnail = thumbnail;
+ this._callWatcher.resumeRecording();
+ }
+});
+
+/**
+ * A collection of methods for manipulating canvas contexts.
+ */
+var ContextUtils = {
+ /**
+ * WebGL contexts are sensitive to how they're queried. Use this function
+ * to make sure the right context is always retrieved, if available.
+ *
+ * @param HTMLCanvasElement canvas
+ * The canvas element for which to get a WebGL context.
+ * @param WebGLRenderingContext gl
+ * The queried WebGL context, or null if unavailable.
+ */
+ getWebGLContext: function (canvas) {
+ return canvas.getContext("webgl") ||
+ canvas.getContext("experimental-webgl");
+ },
+
+ /**
+ * Gets a hold of the rendered pixels in the most efficient way possible for
+ * a canvas with a WebGL context.
+ *
+ * @param WebGLRenderingContext gl
+ * The WebGL context to get a screenshot from.
+ * @param number srcX [optional]
+ * The first left pixel that is read from the framebuffer.
+ * @param number srcY [optional]
+ * The first top pixel that is read from the framebuffer.
+ * @param number srcWidth [optional]
+ * The number of pixels to read on the X axis.
+ * @param number srcHeight [optional]
+ * The number of pixels to read on the Y axis.
+ * @param number dstHeight [optional]
+ * The desired generated screenshot height.
+ * @return object
+ * An objet containing the screenshot's width, height and pixel data,
+ * represented as an 8-bit array buffer of r, g, b, a values.
+ */
+ getPixelsForWebGL: function (gl,
+ srcX = 0, srcY = 0,
+ srcWidth = gl.canvas.width,
+ srcHeight = gl.canvas.height,
+ dstHeight = srcHeight)
+ {
+ let contentPixels = ContextUtils.getPixelStorage(srcWidth, srcHeight);
+ let { "8bit": charView, "32bit": intView } = contentPixels;
+ gl.readPixels(srcX, srcY, srcWidth, srcHeight, gl.RGBA, gl.UNSIGNED_BYTE, charView);
+ return this.resizePixels(intView, srcWidth, srcHeight, dstHeight);
+ },
+
+ /**
+ * Gets a hold of the rendered pixels in the most efficient way possible for
+ * a canvas with a 2D context.
+ *
+ * @param CanvasRenderingContext2D ctx
+ * The 2D context to get a screenshot from.
+ * @param number srcX [optional]
+ * The first left pixel that is read from the canvas.
+ * @param number srcY [optional]
+ * The first top pixel that is read from the canvas.
+ * @param number srcWidth [optional]
+ * The number of pixels to read on the X axis.
+ * @param number srcHeight [optional]
+ * The number of pixels to read on the Y axis.
+ * @param number dstHeight [optional]
+ * The desired generated screenshot height.
+ * @return object
+ * An objet containing the screenshot's width, height and pixel data,
+ * represented as an 8-bit array buffer of r, g, b, a values.
+ */
+ getPixelsFor2D: function (ctx,
+ srcX = 0, srcY = 0,
+ srcWidth = ctx.canvas.width,
+ srcHeight = ctx.canvas.height,
+ dstHeight = srcHeight)
+ {
+ let { data } = ctx.getImageData(srcX, srcY, srcWidth, srcHeight);
+ let { "32bit": intView } = ContextUtils.usePixelStorage(data.buffer);
+ return this.resizePixels(intView, srcWidth, srcHeight, dstHeight);
+ },
+
+ /**
+ * Resizes the provided pixels to fit inside a rectangle with the specified
+ * height and the same aspect ratio as the source.
+ *
+ * @param Uint32Array srcPixels
+ * The source pixel data, assuming 32bit/pixel and 4 color components.
+ * @param number srcWidth
+ * The source pixel data width.
+ * @param number srcHeight
+ * The source pixel data height.
+ * @param number dstHeight [optional]
+ * The desired resized pixel data height.
+ * @return object
+ * An objet containing the resized pixels width, height and data,
+ * represented as an 8-bit array buffer of r, g, b, a values.
+ */
+ resizePixels: function (srcPixels, srcWidth, srcHeight, dstHeight) {
+ let screenshotRatio = dstHeight / srcHeight;
+ let dstWidth = (srcWidth * screenshotRatio) | 0;
+ let dstPixels = new Uint32Array(dstWidth * dstHeight);
+
+ // If the resized image ends up being completely transparent, returning
+ // an empty array will skip some redundant serialization cycles.
+ let isTransparent = true;
+
+ for (let dstX = 0; dstX < dstWidth; dstX++) {
+ for (let dstY = 0; dstY < dstHeight; dstY++) {
+ let srcX = (dstX / screenshotRatio) | 0;
+ let srcY = (dstY / screenshotRatio) | 0;
+ let cPos = srcX + srcWidth * srcY;
+ let dPos = dstX + dstWidth * dstY;
+ let color = dstPixels[dPos] = srcPixels[cPos];
+ if (color) {
+ isTransparent = false;
+ }
+ }
+ }
+
+ return {
+ width: dstWidth,
+ height: dstHeight,
+ pixels: isTransparent ? [] : new Uint8Array(dstPixels.buffer)
+ };
+ },
+
+ /**
+ * Invokes a series of canvas context calls, to "replay" an animation frame
+ * and generate a screenshot.
+ *
+ * In case of a WebGL context, an offscreen framebuffer is created for
+ * the respective canvas, and the rendering will be performed into it.
+ * This is necessary because some state (like shaders, textures etc.) can't
+ * be shared between two different WebGL contexts.
+ * - Hopefully, once SharedResources are a thing this won't be necessary:
+ * http://www.khronos.org/webgl/wiki/SharedResouces
+ * - Alternatively, we could pursue the idea of using the same context
+ * for multiple canvases, instead of trying to share resources:
+ * https://www.khronos.org/webgl/public-mailing-list/archives/1210/msg00058.html
+ *
+ * In case of a 2D context, a new canvas is created, since there's no
+ * intrinsic state that can't be easily duplicated.
+ *
+ * @param number contexType
+ * The type of context to use. See the CallWatcherFront scope types.
+ * @param HTMLCanvasElement canvas
+ * The canvas element which is the source of all context calls.
+ * @param array calls
+ * An array of function call actors.
+ * @param number first
+ * The first function call to start from.
+ * @param number last
+ * The last (inclusive) function call to end at.
+ * @return object
+ * The context on which the specified calls were invoked, the
+ * last registered draw call's index and a cleanup function, which
+ * needs to be called whenever any potential followup work is finished.
+ */
+ replayAnimationFrame: function ({ contextType, canvas, calls, first, last }) {
+ let w = canvas.width;
+ let h = canvas.height;
+
+ let replayContext;
+ let replayContextScaling;
+ let customViewport;
+ let customFramebuffer;
+ let lastDrawCallIndex = -1;
+ let doCleanup = () => {};
+
+ // In case of WebGL contexts, rendering will be done offscreen, in a
+ // custom framebuffer, but using the same provided context. This is
+ // necessary because it's very memory-unfriendly to rebuild all the
+ // required GL state (like recompiling shaders, setting global flags, etc.)
+ // in an entirely new canvas. However, special care is needed to not
+ // permanently affect the existing GL state in the process.
+ if (contextType == "WebGLRenderingContext") {
+ // To keep things fast, replay the context calls on a framebuffer
+ // of smaller dimensions than the actual canvas (maximum 256x256 pixels).
+ let scaling = Math.min(CanvasFront.WEBGL_SCREENSHOT_MAX_HEIGHT, h) / h;
+ replayContextScaling = scaling;
+ w = (w * scaling) | 0;
+ h = (h * scaling) | 0;
+
+ // Fetch the same WebGL context and bind a new framebuffer.
+ let gl = replayContext = this.getWebGLContext(canvas);
+ let { newFramebuffer, oldFramebuffer } = this.createBoundFramebuffer(gl, w, h);
+ customFramebuffer = newFramebuffer;
+
+ // Set the viewport to match the new framebuffer's dimensions.
+ let { newViewport, oldViewport } = this.setCustomViewport(gl, w, h);
+ customViewport = newViewport;
+
+ // Revert the framebuffer and viewport to the original values.
+ doCleanup = () => {
+ gl.bindFramebuffer(gl.FRAMEBUFFER, oldFramebuffer);
+ gl.viewport.apply(gl, oldViewport);
+ };
+ }
+ // In case of 2D contexts, draw everything on a separate canvas context.
+ else if (contextType == "CanvasRenderingContext2D") {
+ let contentDocument = canvas.ownerDocument;
+ let replayCanvas = contentDocument.createElement("canvas");
+ replayCanvas.width = w;
+ replayCanvas.height = h;
+ replayContext = replayCanvas.getContext("2d");
+ replayContextScaling = 1;
+ customViewport = [0, 0, w, h];
+ }
+
+ // Replay all the context calls up to and including the specified one.
+ for (let i = first; i <= last; i++) {
+ let { type, name, args } = calls[i].details;
+
+ // Prevent WebGL context calls that try to reset the framebuffer binding
+ // to the default value, since we want to perform the rendering offscreen.
+ if (name == "bindFramebuffer" && args[1] == null) {
+ replayContext.bindFramebuffer(replayContext.FRAMEBUFFER, customFramebuffer);
+ continue;
+ }
+ // Also prevent WebGL context calls that try to change the viewport
+ // while our custom framebuffer is bound.
+ if (name == "viewport") {
+ let framebufferBinding = replayContext.getParameter(replayContext.FRAMEBUFFER_BINDING);
+ if (framebufferBinding == customFramebuffer) {
+ replayContext.viewport.apply(replayContext, customViewport);
+ continue;
+ }
+ }
+ if (type == CallWatcherFront.METHOD_FUNCTION) {
+ replayContext[name].apply(replayContext, args);
+ } else if (type == CallWatcherFront.SETTER_FUNCTION) {
+ replayContext[name] = args;
+ }
+ if (CanvasFront.DRAW_CALLS.has(name)) {
+ lastDrawCallIndex = i;
+ }
+ }
+
+ return {
+ replayContext: replayContext,
+ replayContextScaling: replayContextScaling,
+ replayViewport: customViewport,
+ lastDrawCallIndex: lastDrawCallIndex,
+ doCleanup: doCleanup
+ };
+ },
+
+ /**
+ * Gets an object containing a buffer large enough to hold width * height
+ * pixels, assuming 32bit/pixel and 4 color components.
+ *
+ * This method avoids allocating memory and tries to reuse a common buffer
+ * as much as possible.
+ *
+ * @param number w
+ * The desired pixel array storage width.
+ * @param number h
+ * The desired pixel array storage height.
+ * @return object
+ * The requested pixel array buffer.
+ */
+ getPixelStorage: function (w = 0, h = 0) {
+ let storage = this._currentPixelStorage;
+ if (storage && storage["32bit"].length >= w * h) {
+ return storage;
+ }
+ return this.usePixelStorage(new ArrayBuffer(w * h * 4));
+ },
+
+ /**
+ * Creates and saves the array buffer views used by `getPixelStorage`.
+ *
+ * @param ArrayBuffer buffer
+ * The raw buffer used as storage for various array buffer views.
+ */
+ usePixelStorage: function (buffer) {
+ let array8bit = new Uint8Array(buffer);
+ let array32bit = new Uint32Array(buffer);
+ return this._currentPixelStorage = {
+ "8bit": array8bit,
+ "32bit": array32bit
+ };
+ },
+
+ /**
+ * Creates a framebuffer of the specified dimensions for a WebGL context,
+ * assuming a RGBA color buffer, a depth buffer and no stencil buffer.
+ *
+ * @param WebGLRenderingContext gl
+ * The WebGL context to create and bind a framebuffer for.
+ * @param number width
+ * The desired width of the renderbuffers.
+ * @param number height
+ * The desired height of the renderbuffers.
+ * @return WebGLFramebuffer
+ * The generated framebuffer object.
+ */
+ createBoundFramebuffer: function (gl, width, height) {
+ let oldFramebuffer = gl.getParameter(gl.FRAMEBUFFER_BINDING);
+ let oldRenderbufferBinding = gl.getParameter(gl.RENDERBUFFER_BINDING);
+ let oldTextureBinding = gl.getParameter(gl.TEXTURE_BINDING_2D);
+
+ let newFramebuffer = gl.createFramebuffer();
+ gl.bindFramebuffer(gl.FRAMEBUFFER, newFramebuffer);
+
+ // Use a texture as the color renderbuffer attachment, since consumers of
+ // this function will most likely want to read the rendered pixels back.
+ let colorBuffer = gl.createTexture();
+ gl.bindTexture(gl.TEXTURE_2D, colorBuffer);
+ gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
+ gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
+ gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
+ gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
+ gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, width, height, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
+
+ let depthBuffer = gl.createRenderbuffer();
+ gl.bindRenderbuffer(gl.RENDERBUFFER, depthBuffer);
+ gl.renderbufferStorage(gl.RENDERBUFFER, gl.DEPTH_COMPONENT16, width, height);
+
+ gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, colorBuffer, 0);
+ gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.RENDERBUFFER, depthBuffer);
+
+ gl.bindTexture(gl.TEXTURE_2D, oldTextureBinding);
+ gl.bindRenderbuffer(gl.RENDERBUFFER, oldRenderbufferBinding);
+
+ return { oldFramebuffer, newFramebuffer };
+ },
+
+ /**
+ * Sets the viewport of the drawing buffer for a WebGL context.
+ * @param WebGLRenderingContext gl
+ * @param number width
+ * @param number height
+ */
+ setCustomViewport: function (gl, width, height) {
+ let oldViewport = XPCNativeWrapper.unwrap(gl.getParameter(gl.VIEWPORT));
+ let newViewport = [0, 0, width, height];
+ gl.viewport.apply(gl, newViewport);
+
+ return { oldViewport, newViewport };
+ }
+};
+
+/**
+ * Goes through all the arguments and creates a one-level shallow copy
+ * of all arrays and array buffers.
+ */
+function inplaceShallowCloneArrays(functionArguments, contentWindow) {
+ let { Object, Array, ArrayBuffer } = contentWindow;
+
+ functionArguments.forEach((arg, index, store) => {
+ if (arg instanceof Array) {
+ store[index] = arg.slice();
+ }
+ if (arg instanceof Object && arg.buffer instanceof ArrayBuffer) {
+ store[index] = new arg.constructor(arg);
+ }
+ });
+}