scratchjr/src/utils/Events.js

/*
the caller should define the window event and call startDrag with the appropiate values
*/

import {gn, scaleMultiplier, isTablet} from './lib';

let dragged = false;
let dragthumbnail = undefined;
let dragmousex = 0;
let dragmousey = 0;
let timeoutEvent = undefined;
let dragcanvas = undefined;
let dragDiv = undefined;
let fcnstart = undefined;
let fcnend = undefined;
let updatefcn = undefined;
let fcnclick = undefined;
let scaleStartsAt = 1;
let delta = 10;
let pinchcenter = {
    x: 0,
    y: 0,
    distance: 0
};
let lastZoomScale = 1;

export default class Events {
    // Getters/setters for globally used properties
    static get dragged () {
        return dragged;
    }

    static set dragged (newDragged) {
        dragged = newDragged;
    }

    static get dragthumbnail () {
        return dragthumbnail;
    }

    static set dragthumbnail (newDragthumbnail) {
        dragthumbnail = newDragthumbnail;
    }

    static get dragmousex () {
        return dragmousex;
    }

    static set dragmousex (newDragmousex) {
        dragmousex = newDragmousex;
    }

    static get dragmousey () {
        return dragmousey;
    }

    static set dragmousey (newDragmousey) {
        dragmousey = newDragmousey;
    }

    static get timeoutEvent () {
        return timeoutEvent;
    }

    static set timeoutEvent (newTimeoutEvent) {
        timeoutEvent = newTimeoutEvent;
    }

    static get dragcanvas () {
        return dragcanvas;
    }

    static set dragcanvas (newDragcanvas) {
        dragcanvas = newDragcanvas;
    }

    static get dragDiv () {
        return dragDiv;
    }

    static get scaleStartsAt () {
        return scaleStartsAt;
    }

    static set scaleStartsAt (newScaleStartsAt) {
        scaleStartsAt = newScaleStartsAt;
    }

    static get pinchcenter () {
        return pinchcenter;
    }

    // Instead of popping the dragging block, etc to the outer-most frame,
    // which causes delays while the content is reflowed, we create a
    // small drag div that is a parent of frame that the dragging block
    // can be a child of. This improves dragging performance.
    static init () {
        var dragDiv = document.createElement('div');
        dragDiv.id = 'dragDiv';
        dragDiv.style.position = 'absolute';
        dragDiv.style.width = '0px'; // size doesn't matter since children float
        dragDiv.style.height = '0px';
        dragDiv.style.zIndex = 7001; // slightly higher than ScratchJr.dragginLayer
        var frameDiv = gn('frame');
        frameDiv.appendChild(dragDiv);
        dragDiv = dragDiv;
    }
    static startDrag (e, c, atstart, atend, atdrag, atclick, athold) {
        dragged = false;
        var pt = Events.getTargetPoint(e);
        dragmousex = pt.x;
        dragmousey = pt.y;
        dragthumbnail = c;
        fcnstart = atstart;
        fcnend = atend;
        fcnclick = atclick;

        if (athold) {
            Events.holdit(c, athold);
        }
        updatefcn = atdrag;
        if (isTablet) { // startDrag event setting
            delta = 10 * scaleMultiplier;
            window.ontouchmove = function (evt) {
                Events.mouseMove(evt);
            };
            window.ontouchend = function (evt) {
                Events.mouseUp(evt);
            };
            window.ontouchleave = function (evt) {
                Events.mouseUp(evt);
            };
            window.ontouchcancel = function (evt) {
                Events.mouseUp(evt);
            };
        } else {
            delta = 7;
            window.onmousemove = function (evt) {
                Events.mouseMove(evt);
            };
            window.onmouseup = function (evt) {
                Events.mouseUp(evt);
            };
        }
    }

    static holdit (c, fcn) {
        var repeat = function () {
            Events.clearEvents();
            fcn(dragthumbnail);
            Events.clearDragAndDrop();
        };
        timeoutEvent = setTimeout(repeat, 500);
    }

    static clearDragAndDrop () {
        timeoutEvent = undefined;
        dragcanvas = undefined;
        dragged = false;
        dragthumbnail = undefined;
        fcnstart = undefined;
        fcnend = undefined;
        updatefcn = undefined;
        fcnclick = undefined;
    }

    static mouseMove (e) {
        // be forgiving about the click
        var pt = Events.getTargetPoint(e);
        if (!dragged && (Events.distance(dragmousex - pt.x, dragmousey - pt.y) < delta)) {
            return;
        }
        if (timeoutEvent) {
            clearTimeout(timeoutEvent);
        }
        timeoutEvent = undefined;
        if (!dragged) {
            fcnstart(e);
        }
        dragged = true;
        if (updatefcn) {
            updatefcn(e, dragcanvas);
        }
        dragmousex = pt.x;
        dragmousey = pt.y;
    }

    static distance (dx, dy) {
        return Math.round(Math.sqrt((dx * dx) + (dy * dy)));
    }

    static mouseUp (e) {
        if (timeoutEvent) {
            clearTimeout(timeoutEvent);
        }
        timeoutEvent = undefined;
        Events.clearEvents();
        if (!dragged) {
            Events.itIsAClick(e);
        } else {
            Events.performMouseUpAction(e);
        }
        Events.clearDragAndDrop();
    }

    static cancelAll () {
        if (timeoutEvent) {
            clearTimeout(timeoutEvent);
        }
        timeoutEvent = undefined;
        Events.clearEvents();
    }

    static clearEvents () {
        if (isTablet) { // clearEvents
            window.ontouchmove = undefined;
            window.ontouchend = undefined;
        } else {
            window.onmousemove = function (e) {
                e.preventDefault();
            };
            window.onmouseup = undefined;
        }
    }

    static performMouseUpAction (e) {
        if (fcnend) {
            fcnend(e, dragcanvas);
        }
    }

    static itIsAClick (e) {
        if (fcnclick) {
            fcnclick(e, dragthumbnail);
        }
    }

    static moveThumbnail (el, dx, dy) {
        if (!el) {
            return;
        }
        el.top += dy;
        el.left += dx;
        el.style.top = el.top + 'px';
        el.style.left = el.left + 'px';
    }

    static move3D (el, dx, dy) {
        if (!el) {
            return;
        }
        var mtx = new WebKitCSSMatrix(window.getComputedStyle(el).webkitTransform);
        el.top = dy + mtx.m42;
        el.left = dx + mtx.m41;
        el.style.webkitTransform = 'translate3d(' + el.left + 'px,' + el.top + 'px, 0)';
    }


    /*
    .m41 – corresponds to the ‘x’ value of a WebKitCSSMatrix
    .m42 – corresponds to the ‘y’ value of a WebKitCSSMatrix
    */

    static getTargetPoint (e) {
        if (isTablet) {
            if (e.touches && (e.touches.length > 0)) {
                return {
                    x: e.touches[0].pageX,
                    y: e.touches[0].pageY
                };
            } else if (e.changedTouches) {
                return {
                    x: e.changedTouches[0].pageX,
                    y: e.changedTouches[0].pageY
                };
            }
        }
        return {
            x: e.clientX,
            y: e.clientY
        };
    }

    static updatePinchCenter (e) {
        if (e.touches.length != 2) {
            return;
        }
        var x1 = e.touches[0].clientX,
            y1 = e.touches[0].clientY;
        var x2 = e.touches[1].clientX,
            y2 = e.touches[1].clientY;
        var cx = x1 + (x2 - x1) / 2,
            cy = y1 + (y2 - y1) / 2;
        var d = Math.sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
        pinchcenter = {
            x: cx,
            y: cy,
            distance: d
        };
    }

    static zoomScale (e) {
        if (e.touches.length !== 2) {
            return lastZoomScale;
        }
        var x1 = e.touches[0].clientX,
            y1 = e.touches[0].clientY;
        var x2 = e.touches[1].clientX,
            y2 = e.touches[1].clientY;
        var d = Math.sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
        lastZoomScale = d / pinchcenter.distance;
        return lastZoomScale;
    }
}