The Tor Browser: browser/devtools/shared/widgets/CSSTransformPreviewer.js@925c144e1f1f (annotated)

browser/devtools/shared/widgets/CSSTransformPreviewer.js@925c144e1f1f (annotated)

browser/devtools/shared/widgets/CSSTransformPreviewer.js

Fri, 16 Jan 2015 18:13:44 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Fri, 16 Jan 2015 18:13:44 +0100
branch: TOR_BUG_9701
changeset 14: 925c144e1f1f
permissions: -rw-r--r--

Integrate suggestion from review to improve consistency with existing code.

 /* 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";
 /**
  * The CSSTransformPreview module displays, using a <canvas> a rectangle, with
  * a given width and height and its transformed version, given a css transform
  * property and origin. It also displays arrows from/to each corner.
  *
  * It is useful to visualize how a css transform affected an element. It can
  * help debug tricky transformations. It is used today in a tooltip, and this
  * tooltip is shown when hovering over a css transform declaration in the rule
  * and computed view panels.
  *
  * TODO: For now, it multiplies matrices itself to calculate the coordinates of
  * the transformed box, but that should be removed as soon as we can get access
  * to getQuads().
  */
 const HTML_NS = "http://www.w3.org/1999/xhtml";
 /**
  * The TransformPreview needs an element to output a canvas tag.
  *
  * Usage example:
  *
  * let t = new CSSTransformPreviewer(myRootElement);
  * t.preview("rotate(45deg)", "top left", 200, 400);
  * t.preview("skew(19deg)", "center", 100, 500);
  * t.preview("matrix(1, -0.2, 0, 1, 0, 0)");
  * t.destroy();
  *
  * @param {nsIDOMElement} parentEl
  *        Where the canvas will go
  */
 function CSSTransformPreviewer(parentEl) {
   this.parentEl = parentEl;
   this.doc = this.parentEl.ownerDocument;
   this.canvas = null;
   this.ctx = null;
 }
 module.exports.CSSTransformPreviewer = CSSTransformPreviewer;
 CSSTransformPreviewer.prototype = {
   /**
    * The preview look-and-feel can be changed using these properties
    */
   MAX_DIM: 250,
   PAD: 5,
   ORIGINAL_FILL: "#1F303F",
   ORIGINAL_STROKE: "#B2D8FF",
   TRANSFORMED_FILL: "rgba(200, 200, 200, .5)",
   TRANSFORMED_STROKE: "#B2D8FF",
   ARROW_STROKE: "#329AFF",
   ORIGIN_STROKE: "#329AFF",
   ARROW_TIP_HEIGHT: 10,
   ARROW_TIP_WIDTH: 8,
   CORNER_SIZE_RATIO: 6,
   /**
    * Destroy removes the canvas from the parentelement passed in the constructor
    */
   destroy: function() {
     if (this.canvas) {
       this.parentEl.removeChild(this.canvas);
     }
     if (this._hiddenDiv) {
       this.parentEl.removeChild(this._hiddenDiv);
     }
     this.parentEl = this.canvas = this.ctx = this.doc = null;
   },
   _createMarkup: function() {
     this.canvas = this.doc.createElementNS(HTML_NS, "canvas");
     this.canvas.setAttribute("id", "canvas");
     this.canvas.setAttribute("width", this.MAX_DIM);
     this.canvas.setAttribute("height", this.MAX_DIM);
     this.canvas.style.position = "relative";
     this.parentEl.appendChild(this.canvas);
     this.ctx = this.canvas.getContext("2d");
   },
   _getComputed: function(name, value, width, height) {
     if (!this._hiddenDiv) {
       // Create a hidden element to apply the style to
       this._hiddenDiv = this.doc.createElementNS(HTML_NS, "div");
       this._hiddenDiv.style.visibility = "hidden";
       this._hiddenDiv.style.position = "absolute";
       this.parentEl.appendChild(this._hiddenDiv);
     }
     // Camelcase the name
     name = name.replace(/-([a-z]{1})/g, (m, letter) => letter.toUpperCase());
     // Apply width and height to make sure computation is made correctly
     this._hiddenDiv.style.width = width + "px";
     this._hiddenDiv.style.height = height + "px";
     // Show the hidden div, apply the style, read the computed style, hide the
     // hidden div again
     this._hiddenDiv.style.display = "block";
     this._hiddenDiv.style[name] = value;
     let computed = this.doc.defaultView.getComputedStyle(this._hiddenDiv);
     let computedValue = computed[name];
     this._hiddenDiv.style.display = "none";
     return computedValue;
   },
   _getMatrixFromTransformString: function(transformStr) {
     let matrix = transformStr.substring(0, transformStr.length - 1).
       substring(transformStr.indexOf("(") + 1).split(",");
     matrix.forEach(function(value, index) {
       matrix[index] = parseFloat(value, 10);
     });
     let transformMatrix = null;
     if (matrix.length === 6) {
       // 2d transform
       transformMatrix = [
         [matrix[0], matrix[2], matrix[4], 0],
         [matrix[1], matrix[3], matrix[5], 0],
         [0,     0,     1,     0],
         [0,     0,     0,     1]
       ];
     } else {
       // 3d transform
       transformMatrix = [
         [matrix[0], matrix[4], matrix[8],  matrix[12]],
         [matrix[1], matrix[5], matrix[9],  matrix[13]],
         [matrix[2], matrix[6], matrix[10], matrix[14]],
         [matrix[3], matrix[7], matrix[11], matrix[15]]
       ];
     }
     return transformMatrix;
   },
   _getOriginFromOriginString: function(originStr) {
     let offsets = originStr.split(" ");
     offsets.forEach(function(item, index) {
       offsets[index] = parseInt(item, 10);
     });
     return offsets;
   },
   _multiply: function(m1, m2) {
     let m = [];
     for (let m1Line = 0; m1Line < m1.length; m1Line++) {
       m[m1Line] = 0;
       for (let m2Col = 0; m2Col < m2.length; m2Col++) {
         m[m1Line] += m1[m1Line][m2Col] * m2[m2Col];
       }
     }
     return [m[0], m[1]];
   },
   _getTransformedPoint: function(matrix, point, origin) {
     let pointMatrix = [point[0] - origin[0], point[1] - origin[1], 1, 1];
     return this._multiply(matrix, pointMatrix);
   },
   _getTransformedPoints: function(matrix, rect, origin) {
     return rect.map(point => {
       let tPoint = this._getTransformedPoint(matrix, [point[0], point[1]], origin);
       return [tPoint[0] + origin[0], tPoint[1] + origin[1]];
     });
   },
   /**
    * For canvas to avoid anti-aliasing
    */
   _round: x => Math.round(x) + .5,
   _drawShape: function(points, fillStyle, strokeStyle) {
     this.ctx.save();
     this.ctx.lineWidth = 1;
     this.ctx.strokeStyle = strokeStyle;
     this.ctx.fillStyle = fillStyle;
     this.ctx.beginPath();
     this.ctx.moveTo(this._round(points[0][0]), this._round(points[0][1]));
     for (var i = 1; i < points.length; i++) {
       this.ctx.lineTo(this._round(points[i][0]), this._round(points[i][1]));
     }
     this.ctx.lineTo(this._round(points[0][0]), this._round(points[0][1]));
     this.ctx.fill();
     this.ctx.stroke();
     this.ctx.restore();
   },
   _drawArrow: function(x1, y1, x2, y2) {
     // do not draw if the line is too small
     if (Math.abs(x2-x1) < 20 && Math.abs(y2-y1) < 20) {
       return;
     }
     this.ctx.save();
     this.ctx.strokeStyle = this.ARROW_STROKE;
     this.ctx.fillStyle = this.ARROW_STROKE;
     this.ctx.lineWidth = 1;
     this.ctx.beginPath();
     this.ctx.moveTo(this._round(x1), this._round(y1));
     this.ctx.lineTo(this._round(x2), this._round(y2));
     this.ctx.stroke();
     this.ctx.beginPath();
     this.ctx.translate(x2, y2);
     let radians = Math.atan((y1 - y2) / (x1 - x2));
     radians += ((x1 >= x2) ? -90 : 90) * Math.PI / 180;
     this.ctx.rotate(radians);
     this.ctx.moveTo(0, 0);
     this.ctx.lineTo(this.ARROW_TIP_WIDTH / 2, this.ARROW_TIP_HEIGHT);
     this.ctx.lineTo(-this.ARROW_TIP_WIDTH / 2, this.ARROW_TIP_HEIGHT);
     this.ctx.closePath();
     this.ctx.fill();
     this.ctx.restore();
   },
   _drawOrigin: function(x, y) {
     this.ctx.save();
     this.ctx.strokeStyle = this.ORIGIN_STROKE;
     this.ctx.fillStyle = this.ORIGIN_STROKE;
     this.ctx.beginPath();
     this.ctx.arc(x, y, 4, 0, 2 * Math.PI, false);
     this.ctx.stroke();
     this.ctx.fill();
     this.ctx.restore();
   },
   /**
    * Computes the largest width and height of all the given shapes and changes
    * all of the shapes' points (by reference) so they fit into the configured
    * MAX_DIM - 2*PAD area.
    * @return {Object} A {w, h} giving the size the canvas should be
    */
   _fitAllShapes: function(allShapes) {
     let allXs = [], allYs = [];
     for (let shape of allShapes) {
       for (let point of shape) {
         allXs.push(point[0]);
         allYs.push(point[1]);
       }
     }
     let minX = Math.min.apply(Math, allXs);
     let maxX = Math.max.apply(Math, allXs);
     let minY = Math.min.apply(Math, allYs);
     let maxY = Math.max.apply(Math, allYs);
     let spanX = maxX - minX;
     let spanY = maxY - minY;
     let isWide = spanX > spanY;
     let cw = isWide ? this.MAX_DIM :
       this.MAX_DIM * Math.min(spanX, spanY) / Math.max(spanX, spanY);
     let ch = !isWide ? this.MAX_DIM :
       this.MAX_DIM * Math.min(spanX, spanY) / Math.max(spanX, spanY);
     let mapX = x => this.PAD + ((cw - 2 * this.PAD) / (maxX - minX)) * (x - minX);
     let mapY = y => this.PAD + ((ch - 2 * this.PAD) / (maxY - minY)) * (y - minY);
     for (let shape of allShapes) {
       for (let point of shape) {
         point[0] = mapX(point[0]);
         point[1] = mapY(point[1]);
       }
     }
     return {w: cw, h: ch};
   },
   _drawShapes: function(shape, corner, transformed, transformedCorner) {
     this._drawOriginal(shape);
     this._drawOriginalCorner(corner);
     this._drawTransformed(transformed);
     this._drawTransformedCorner(transformedCorner);
   },
   _drawOriginal: function(points) {
     this._drawShape(points, this.ORIGINAL_FILL, this.ORIGINAL_STROKE);
   },
   _drawTransformed: function(points) {
     this._drawShape(points, this.TRANSFORMED_FILL, this.TRANSFORMED_STROKE);
   },
   _drawOriginalCorner: function(points) {
     this._drawShape(points, this.ORIGINAL_STROKE, this.ORIGINAL_STROKE);
   },
   _drawTransformedCorner: function(points) {
     this._drawShape(points, this.TRANSFORMED_STROKE, this.TRANSFORMED_STROKE);
   },
   _drawArrows: function(shape, transformed) {
     this._drawArrow(shape[0][0], shape[0][1], transformed[0][0], transformed[0][1]);
     this._drawArrow(shape[1][0], shape[1][1], transformed[1][0], transformed[1][1]);
     this._drawArrow(shape[2][0], shape[2][1], transformed[2][0], transformed[2][1]);
     this._drawArrow(shape[3][0], shape[3][1], transformed[3][0], transformed[3][1]);
   },
   /**
    * Draw a transform preview
    *
    * @param {String} transform
    *        The css transform value as a string, as typed by the user, as long
    *        as it can be computed by the browser
    * @param {String} origin
    *        Same as above for the transform-origin value. Defaults to "center"
    * @param {Number} width
    *        The width of the container. Defaults to 200
    * @param {Number} height
    *        The height of the container. Defaults to 200
    * @return {Boolean} Whether or not the preview could be created. Will return
    *         false for instance if the transform is invalid
    */
   preview: function(transform, origin="center", width=200, height=200) {
     // Create/clear the canvas
     if (!this.canvas) {
       this._createMarkup();
     }
     this.ctx.clearRect(0, 0, this.canvas.width, this.canvas.height);
     // Get computed versions of transform and origin
     transform = this._getComputed("transform", transform, width, height);
     if (transform && transform !== "none") {
       origin = this._getComputed("transform-origin", origin, width, height);
       // Get the matrix, origin and width height data for the previewed element
       let originData = this._getOriginFromOriginString(origin);
       let matrixData = this._getMatrixFromTransformString(transform);
       // Compute the original box rect and transformed box rect
       let shapePoints = [
         [0, 0],
         [width, 0],
         [width, height],
         [0, height]
       ];
       let transformedPoints = this._getTransformedPoints(matrixData, shapePoints, originData);
       // Do the same for the corner triangle shape
       let cornerSize = Math.min(shapePoints[2][1] - shapePoints[1][1],
         shapePoints[1][0] - shapePoints[0][0]) / this.CORNER_SIZE_RATIO;
       let cornerPoints = [
         [shapePoints[1][0], shapePoints[1][1]],
         [shapePoints[1][0], shapePoints[1][1] + cornerSize],
         [shapePoints[1][0] - cornerSize, shapePoints[1][1]]
       ];
       let transformedCornerPoints = this._getTransformedPoints(matrixData, cornerPoints, originData);
       // Resize points to fit everything in the canvas
       let {w, h} = this._fitAllShapes([
         shapePoints,
         transformedPoints,
         cornerPoints,
         transformedCornerPoints,
         [originData]
       ]);
       this.canvas.setAttribute("width", w);
       this.canvas.setAttribute("height", h);
       this._drawShapes(shapePoints, cornerPoints, transformedPoints, transformedCornerPoints)
       this._drawArrows(shapePoints, transformedPoints);
       this._drawOrigin(originData[0], originData[1]);
       return true;
     } else {
       return false;
     }
   }
 };