phaser/src/system/Canvas.js

/**
* @author       Richard Davey <rich@photonstorm.com>
* @copyright    2013 Photon Storm Ltd.
* @license      {@link https://github.com/photonstorm/phaser/blob/master/license.txt|MIT License}
*/

/**
* The Canvas class handles everything related to creating the `canvas` DOM tag that Phaser will use, including styles, offset and aspect ratio.
*
* @class Phaser.Canvas
* @static
*/
Phaser.Canvas = {

    /**
    * Creates a `canvas` DOM element. The element is not automatically added to the document.
    *
    * @method Phaser.Canvas.create
    * @param {number} [width=256] - The width of the canvas element.
    * @param {number} [height=256] - The height of the canvas element..
    * @param {string} [id=''] - If given this will be set as the ID of the canvas element, otherwise no ID will be set.
    * @return {HTMLCanvasElement} The newly created canvas element.
    */
    create: function (width, height, id) {

        width = width || 256;
        height = height || 256;

        var canvas = document.createElement('canvas');

        if (typeof id === 'string')
        {
            canvas.id = id;
        }

        canvas.width = width;
        canvas.height = height;

        canvas.style.display = 'block';

        return canvas;

    },

    /**
    * Get the DOM offset values of any given element
    * @method Phaser.Canvas.getOffset
    * @param {HTMLElement} element - The targeted element that we want to retrieve the offset.
    * @param {Phaser.Point} [point] - The point we want to take the x/y values of the offset.
    * @return {Phaser.Point} - A point objet with the offsetX and Y as its properties.
    */
    getOffset: function (element, point) {

        point = point || new Phaser.Point();

        var box = element.getBoundingClientRect();
        var clientTop = element.clientTop || document.body.clientTop || 0;
        var clientLeft = element.clientLeft || document.body.clientLeft || 0;

        //  Without this check Chrome is now throwing console warnings about strict vs. quirks :(

        var scrollTop = 0;
        var scrollLeft = 0;

        if (document.compatMode === 'CSS1Compat')
        {
            scrollTop = window.pageYOffset || document.documentElement.scrollTop || element.scrollTop || 0;
            scrollLeft = window.pageXOffset || document.documentElement.scrollLeft || element.scrollLeft || 0;
        }
        else
        {
            scrollTop = window.pageYOffset || document.body.scrollTop || element.scrollTop || 0;
            scrollLeft = window.pageXOffset || document.body.scrollLeft || element.scrollLeft || 0;
        }

        point.x = box.left + scrollLeft - clientLeft;
        point.y = box.top + scrollTop - clientTop;

        return point;

    },

    /**
    * Returns the aspect ratio of the given canvas.
    *
    * @method Phaser.Canvas.getAspectRatio
    * @param {HTMLCanvasElement} canvas - The canvas to get the aspect ratio from.
    * @return {number} The ratio between canvas' width and height.
    */
    getAspectRatio: function (canvas) {
        return canvas.width / canvas.height;
    },

    /**
    * Sets the background color behind the canvas. This changes the canvas style property.
    *
    * @method Phaser.Canvas.setBackgroundColor
    * @param {HTMLCanvasElement} canvas - The canvas to set the background color on.
    * @param {string} [color] - The color to set. Can be in the format 'rgb(r,g,b)', or '#RRGGBB' or any valid CSS color.
    * @return {HTMLCanvasElement} Returns the source canvas.
    */
    setBackgroundColor: function (canvas, color) {

        color = color || 'rgb(0,0,0)';

        canvas.style.backgroundColor = color;
        
        return canvas;

    },

    /**
    * Sets the touch-action property on the canvas style. Can be used to disable default browser touch actions.
    *
    * @method Phaser.Canvas.setTouchAction
    * @param {HTMLCanvasElement} canvas - The canvas to set the touch action on.
    * @param {String} [value] - The touch action to set. Defaults to 'none'.
    * @return {HTMLCanvasElement} The source canvas.
    */
    setTouchAction: function (canvas, value) {

        value = value || 'none';

        canvas.style.msTouchAction = value;
        canvas.style['ms-touch-action'] = value;
        canvas.style['touch-action'] = value;

        return canvas;

    },

    /**
    * Sets the user-select property on the canvas style. Can be used to disable default browser selection actions.
    *
    * @method Phaser.Canvas.setUserSelect
    * @param {HTMLCanvasElement} canvas - The canvas to set the touch action on.
    * @param {String} [value] - The touch action to set. Defaults to 'none'.
    * @return {HTMLCanvasElement} The source canvas.
    */
    setUserSelect: function (canvas, value) {

        value = value || 'none';

        canvas.style['-webkit-touch-callout'] = value;
        canvas.style['-webkit-user-select'] = value;
        canvas.style['-khtml-user-select'] = value;
        canvas.style['-moz-user-select'] = value;
        canvas.style['-ms-user-select'] = value;
        canvas.style['user-select'] = value;
        canvas.style['-webkit-tap-highlight-color'] = 'rgba(0, 0, 0, 0)';

        return canvas;

    },

    /**
    * Adds the given canvas element to the DOM. The canvas will be added as a child of the given parent.
    * If no parent is given it will be added as a child of the document.body.
    *
    * @method Phaser.Canvas.addToDOM
    * @param {HTMLCanvasElement} canvas - The canvas to set the touch action on.
    * @param {string|HTMLElement} parent - The DOM element to add the canvas to.
    * @param {boolean} [overflowHidden=true] - If set to true it will add the overflow='hidden' style to the parent DOM element.
    * @return {HTMLCanvasElement} Returns the source canvas.
    */
    addToDOM: function (canvas, parent, overflowHidden) {

        var target;

        if (typeof overflowHidden === 'undefined') { overflowHidden = true; }

        if (parent)
        {
            if (typeof parent === 'string')
            {
                // hopefully an element ID
                target = document.getElementById(parent);
            }
            else if (typeof parent === 'object' && parent.nodeType === 1)
            {
                // quick test for a HTMLelement
                target = parent;
            }
        }

        // Fallback, covers an invalid ID and a non HTMLelement object
        if (!target)
        {
            target = document.body;
        }

        if (overflowHidden && target.style)
        {
            target.style.overflow = 'hidden';
        }

        target.appendChild(canvas);

        return canvas;

    },

    /**
    * Sets the transform of the given canvas to the matrix values provided.
    *
    * @method Phaser.Canvas.setTransform
    * @param {CanvasRenderingContext2D} context - The context to set the transform on.
    * @param {number} translateX - The value to translate horizontally by.
    * @param {number} translateY - The value to translate vertically by.
    * @param {number} scaleX - The value to scale horizontally by.
    * @param {number} scaleY - The value to scale vertically by.
    * @param {number} skewX - The value to skew horizontaly by.
    * @param {number} skewY - The value to skew vertically by.
    * @return {CanvasRenderingContext2D} Returns the source context.
    */
    setTransform: function (context, translateX, translateY, scaleX, scaleY, skewX, skewY) {

        context.setTransform(scaleX, skewX, skewY, scaleY, translateX, translateY);

        return context;

    },

    /**
    * Sets the Image Smoothing property on the given context. Set to false to disable image smoothing.
    * By default browsers have image smoothing enabled, which isn't always what you visually want, especially
    * when using pixel art in a game. Note that this sets the property on the context itself, so that any image
    * drawn to the context will be affected. This sets the property across all current browsers but support is
    * patchy on earlier browsers, especially on mobile.
    *
    * @method Phaser.Canvas.setSmoothingEnabled
    * @param {CanvasRenderingContext2D} context - The context to enable or disable the image smoothing on.
    * @param {boolean} value - If set to true it will enable image smoothing, false will disable it.
    * @return {CanvasRenderingContext2D} Returns the source context.
    */
    setSmoothingEnabled: function (context, value) {

        context['imageSmoothingEnabled'] = value;
        context['mozImageSmoothingEnabled'] = value;
        context['oImageSmoothingEnabled'] = value;
        context['webkitImageSmoothingEnabled'] = value;
        context['msImageSmoothingEnabled'] = value;

        return context;

    },

    /**
    * Sets the CSS image-rendering property on the given canvas to be 'crisp' (aka 'optimize contrast on webkit').
    * Note that if this doesn't given the desired result then see the setSmoothingEnabled.
    *
    * @method Phaser.Canvas.setImageRenderingCrisp
    * @param {HTMLCanvasElement} canvas - The canvas to set image-rendering crisp on.
    * @return {HTMLCanvasElement} Returns the source canvas.
    */
    setImageRenderingCrisp: function (canvas) {

        canvas.style['image-rendering'] = 'crisp-edges';
        canvas.style['image-rendering'] = '-moz-crisp-edges';
        canvas.style['image-rendering'] = '-webkit-optimize-contrast';
        canvas.style.msInterpolationMode = 'nearest-neighbor';

        return canvas;

    },

    /**
    * Sets the CSS image-rendering property on the given canvas to be 'bicubic' (aka 'auto').
    * Note that if this doesn't given the desired result then see the CanvasUtils.setSmoothingEnabled method.
    *
    * @method Phaser.Canvas.setImageRenderingBicubic
    * @param {HTMLCanvasElement} canvas The canvas to set image-rendering bicubic on.
    * @return {HTMLCanvasElement} Returns the source canvas.
    */
    setImageRenderingBicubic: function (canvas) {

        canvas.style['image-rendering'] = 'auto';
        canvas.style.msInterpolationMode = 'bicubic';

        return canvas;

    }

};