zoom.js

// Custom reveal.js integration
(function() {
    var isEnabled = true;

    document.querySelector('slides').addEventListener('mousedown', function(event) {
        var modifier = 'altKey';

        var zoomPadding = 20;

        if (event[modifier] && isEnabled) {
            event.preventDefault();

            var bounds = event.target.getBoundingClientRect();

            zoom.to({
                x: bounds.left - zoomPadding,
                y: bounds.top - zoomPadding,
                width: bounds.width + (zoomPadding * 2),
                height: bounds.height + (zoomPadding * 2),
                pan: false
            });
        }
    });

    Slide.on('overviewshown', function() {
        isEnabled = false;
    });
    Slide.on('overviewhidden', function() {
        isEnabled = true;
    });
})();

/*!
 * zoom.js 0.3 (modified for use with reveal.js)
 * http://lab.hakim.se/zoom-js
 * MIT licensed
 *
 * Copyright (C) 2011-2014 Hakim El Hattab, http://hakim.se
 */
var zoom = (function() {

    // The current zoom level (scale)
    var level = 1;

    // The current mouse position, used for panning
    var mouseX = 0,
        mouseY = 0;

    // Timeout before pan is activated
    var panEngageTimeout = -1,
        panUpdateInterval = -1;

    // Check for transform support so that we can fallback otherwise
    var supportsTransforms = 'WebkitTransform' in document.body.style || 'MozTransform' in document.body.style || 'msTransform' in document.body.style || 'OTransform' in document.body.style || 'transform' in document.body.style;

    if (supportsTransforms) {
        // The easing that will be applied when we zoom in/out
        document.body.style.transition = 'transform 0.8s ease';
        document.body.style.OTransition = '-o-transform 0.8s ease';
        document.body.style.msTransition = '-ms-transform 0.8s ease';
        document.body.style.MozTransition = '-moz-transform 0.8s ease';
        document.body.style.WebkitTransition = '-webkit-transform 0.8s ease';
    }

    // Zoom out if the user hits escape
    document.addEventListener('keyup', function(event) {
        if (level !== 1 && event.keyCode === 27) {
            zoom.out();
        }
    });

    // Monitor mouse movement for panning
    document.addEventListener('mousemove', function(event) {
        if (level !== 1) {
            mouseX = event.clientX;
            mouseY = event.clientY;
        }
    });

    /**
     * Applies the CSS required to zoom in, prefers the use of CSS3
     * transforms but falls back on zoom for IE.
     *
     * @param {Object} rect
     * @param {Number} scale
     */
    function magnify(rect, scale) {

        var scrollOffset = getScrollOffset();

        // Ensure a width/height is set
        rect.width = rect.width || 1;
        rect.height = rect.height || 1;

        // Center the rect within the zoomed viewport
        rect.x -= (window.innerWidth - (rect.width * scale)) / 2;
        rect.y -= (window.innerHeight - (rect.height * scale)) / 2;

        if (supportsTransforms) {
            // Reset
            if (scale === 1) {
                document.body.style.transform = '';
                document.body.style.OTransform = '';
                document.body.style.msTransform = '';
                document.body.style.MozTransform = '';
                document.body.style.WebkitTransform = '';
            }
            // Scale
            else {
                var origin = scrollOffset.x + 'px ' + scrollOffset.y + 'px',
                    transform = 'translate(' + -rect.x + 'px,' + -rect.y + 'px) scale(' + scale + ')';

                document.body.style.transformOrigin = origin;
                document.body.style.OTransformOrigin = origin;
                document.body.style.msTransformOrigin = origin;
                document.body.style.MozTransformOrigin = origin;
                document.body.style.WebkitTransformOrigin = origin;

                document.body.style.transform = transform;
                document.body.style.OTransform = transform;
                document.body.style.msTransform = transform;
                document.body.style.MozTransform = transform;
                document.body.style.WebkitTransform = transform;
            }
        } else {
            // Reset
            if (scale === 1) {
                document.body.style.position = '';
                document.body.style.left = '';
                document.body.style.top = '';
                document.body.style.width = '';
                document.body.style.height = '';
                document.body.style.zoom = '';
            }
            // Scale
            else {
                document.body.style.position = 'relative';
                document.body.style.left = (-(scrollOffset.x + rect.x) / scale) + 'px';
                document.body.style.top = (-(scrollOffset.y + rect.y) / scale) + 'px';
                document.body.style.width = (scale * 100) + '%';
                document.body.style.height = (scale * 100) + '%';
                document.body.style.zoom = scale;
            }
        }

        level = scale;

        if (document.documentElement.classList) {
            if (level !== 1) {
                document.documentElement.classList.add('zoomed');
            } else {
                document.documentElement.classList.remove('zoomed');
            }
        }
    }

    /**
     * Pan the document when the mosue cursor approaches the edges
     * of the window.
     */
    function pan() {
        var range = 0.12,
            rangeX = window.innerWidth * range,
            rangeY = window.innerHeight * range,
            scrollOffset = getScrollOffset();

        // Up
        if (mouseY < rangeY) {
            window.scroll(scrollOffset.x, scrollOffset.y - (1 - (mouseY / rangeY)) * (14 / level));
        }
        // Down
        else if (mouseY > window.innerHeight - rangeY) {
            window.scroll(scrollOffset.x, scrollOffset.y + (1 - (window.innerHeight - mouseY) / rangeY) * (14 / level));
        }

        // Left
        if (mouseX < rangeX) {
            window.scroll(scrollOffset.x - (1 - (mouseX / rangeX)) * (14 / level), scrollOffset.y);
        }
        // Right
        else if (mouseX > window.innerWidth - rangeX) {
            window.scroll(scrollOffset.x + (1 - (window.innerWidth - mouseX) / rangeX) * (14 / level), scrollOffset.y);
        }
    }

    function getScrollOffset() {
        return {
            x: window.scrollX !== undefined ? window.scrollX : window.pageXOffset,
            y: window.scrollY !== undefined ? window.scrollY : window.pageYOffset
        }
    }

    return {
        /**
         * Zooms in on either a rectangle or HTML element.
         *
         * @param {Object} options
         *   - element: HTML element to zoom in on
         *   OR
         *   - x/y: coordinates in non-transformed space to zoom in on
         *   - width/height: the portion of the screen to zoom in on
         *   - scale: can be used instead of width/height to explicitly set scale
         */
        to: function(options) {

            // Due to an implementation limitation we can't zoom in
            // to another element without zooming out first
            if (level !== 1) {
                zoom.out();
            } else {
                options.x = options.x || 0;
                options.y = options.y || 0;

                // If an element is set, that takes precedence
                if (!!options.element) {
                    // Space around the zoomed in element to leave on screen
                    var padding = 20;
                    var bounds = options.element.getBoundingClientRect();

                    options.x = bounds.left - padding;
                    options.y = bounds.top - padding;
                    options.width = bounds.width + (padding * 2);
                    options.height = bounds.height + (padding * 2);
                }

                // If width/height values are set, calculate scale from those values
                if (options.width !== undefined && options.height !== undefined) {
                    options.scale = Math.max(Math.min(window.innerWidth / options.width, window.innerHeight / options.height), 1);
                }

                if (options.scale > 1) {
                    options.x *= options.scale;
                    options.y *= options.scale;

                    magnify(options, options.scale);

                    if (options.pan !== false) {

                        // Wait with engaging panning as it may conflict with the
                        // zoom transition
                        panEngageTimeout = setTimeout(function() {
                            panUpdateInterval = setInterval(pan, 1000 / 60);
                        }, 800);

                    }
                }
            }
        },

        /**
         * Resets the document zoom state to its default.
         */
        out: function() {
            clearTimeout(panEngageTimeout);
            clearInterval(panUpdateInterval);

            magnify({
                x: 0,
                y: 0
            }, 1);

            level = 1;
        },

        // Alias
        magnify: function(options) {
            this.to(options)
        },
        reset: function() {
            this.out()
        },

        zoomLevel: function() {
            return level;
        }
    }

})();