Code comments for how the receieve queue works

[mirror_novnc.git] / core / input / mouse.js

/*
 * noVNC: HTML5 VNC client
 * Copyright (C) 2018 The noVNC Authors
 * Licensed under MPL 2.0 or any later version (see LICENSE.txt)
 */

import * as Log from '../util/logging.js';
import { isTouchDevice } from '../util/browser.js';
import { setCapture, stopEvent, getPointerEvent } from '../util/events.js';

const WHEEL_STEP = 10; // Delta threshold for a mouse wheel step
const WHEEL_STEP_TIMEOUT = 50; // ms
const WHEEL_LINE_HEIGHT = 19;

export default class Mouse {
    constructor(target) {
        this._target = target || document;

        this._doubleClickTimer = null;
        this._lastTouchPos = null;

        this._pos = null;
        this._wheelStepXTimer = null;
        this._wheelStepYTimer = null;
        this._accumulatedWheelDeltaX = 0;
        this._accumulatedWheelDeltaY = 0;

        this._eventHandlers = {
            'mousedown': this._handleMouseDown.bind(this),
            'mouseup': this._handleMouseUp.bind(this),
            'mousemove': this._handleMouseMove.bind(this),
            'mousewheel': this._handleMouseWheel.bind(this),
            'mousedisable': this._handleMouseDisable.bind(this)
        };

        // ===== PROPERTIES =====

        this.touchButton = 1;                 // Button mask (1, 2, 4) for touch devices (0 means ignore clicks)

        // ===== EVENT HANDLERS =====

        this.onmousebutton = () => {}; // Handler for mouse button click/release
        this.onmousemove = () => {}; // Handler for mouse movement
    }

    // ===== PRIVATE METHODS =====

    _resetDoubleClickTimer() {
        this._doubleClickTimer = null;
    }

    _handleMouseButton(e, down) {
        this._updateMousePosition(e);
        let pos = this._pos;

        let bmask;
        if (e.touches || e.changedTouches) {
            // Touch device

            // When two touches occur within 500 ms of each other and are
            // close enough together a double click is triggered.
            if (down == 1) {
                if (this._doubleClickTimer === null) {
                    this._lastTouchPos = pos;
                } else {
                    clearTimeout(this._doubleClickTimer);

                    // When the distance between the two touches is small enough
                    // force the position of the latter touch to the position of
                    // the first.

                    const xs = this._lastTouchPos.x - pos.x;
                    const ys = this._lastTouchPos.y - pos.y;
                    const d = Math.sqrt((xs * xs) + (ys * ys));

                    // The goal is to trigger on a certain physical width, the
                    // devicePixelRatio brings us a bit closer but is not optimal.
                    const threshold = 20 * (window.devicePixelRatio || 1);
                    if (d < threshold) {
                        pos = this._lastTouchPos;
                    }
                }
                this._doubleClickTimer = setTimeout(this._resetDoubleClickTimer.bind(this), 500);
            }
            bmask = this.touchButton;
            // If bmask is set
        } else if (e.which) {
            /* everything except IE */
            bmask = 1 << e.button;
        } else {
            /* IE including 9 */
            bmask = (e.button & 0x1) +      // Left
                    (e.button & 0x2) * 2 +  // Right
                    (e.button & 0x4) / 2;   // Middle
        }

        Log.Debug("onmousebutton " + (down ? "down" : "up") +
                  ", x: " + pos.x + ", y: " + pos.y + ", bmask: " + bmask);
        this.onmousebutton(pos.x, pos.y, down, bmask);

        stopEvent(e);
    }

    _handleMouseDown(e) {
        // Touch events have implicit capture
        if (e.type === "mousedown") {
            setCapture(this._target);
        }

        this._handleMouseButton(e, 1);
    }

    _handleMouseUp(e) {
        this._handleMouseButton(e, 0);
    }

    // Mouse wheel events are sent in steps over VNC. This means that the VNC
    // protocol can't handle a wheel event with specific distance or speed.
    // Therefor, if we get a lot of small mouse wheel events we combine them.
    _generateWheelStepX() {

        if (this._accumulatedWheelDeltaX < 0) {
            this.onmousebutton(this._pos.x, this._pos.y, 1, 1 << 5);
            this.onmousebutton(this._pos.x, this._pos.y, 0, 1 << 5);
        } else if (this._accumulatedWheelDeltaX > 0) {
            this.onmousebutton(this._pos.x, this._pos.y, 1, 1 << 6);
            this.onmousebutton(this._pos.x, this._pos.y, 0, 1 << 6);
        }

        this._accumulatedWheelDeltaX = 0;
    }

    _generateWheelStepY() {

        if (this._accumulatedWheelDeltaY < 0) {
            this.onmousebutton(this._pos.x, this._pos.y, 1, 1 << 3);
            this.onmousebutton(this._pos.x, this._pos.y, 0, 1 << 3);
        } else if (this._accumulatedWheelDeltaY > 0) {
            this.onmousebutton(this._pos.x, this._pos.y, 1, 1 << 4);
            this.onmousebutton(this._pos.x, this._pos.y, 0, 1 << 4);
        }

        this._accumulatedWheelDeltaY = 0;
    }

    _resetWheelStepTimers() {
        window.clearTimeout(this._wheelStepXTimer);
        window.clearTimeout(this._wheelStepYTimer);
        this._wheelStepXTimer = null;
        this._wheelStepYTimer = null;
    }

    _handleMouseWheel(e) {
        this._resetWheelStepTimers();

        this._updateMousePosition(e);

        let dX = e.deltaX;
        let dY = e.deltaY;

        // Pixel units unless it's non-zero.
        // Note that if deltamode is line or page won't matter since we aren't
        // sending the mouse wheel delta to the server anyway.
        // The difference between pixel and line can be important however since
        // we have a threshold that can be smaller than the line height.
        if (e.deltaMode !== 0) {
            dX *= WHEEL_LINE_HEIGHT;
            dY *= WHEEL_LINE_HEIGHT;
        }

        this._accumulatedWheelDeltaX += dX;
        this._accumulatedWheelDeltaY += dY;

        // Generate a mouse wheel step event when the accumulated delta
        // for one of the axes is large enough.
        // Small delta events that do not pass the threshold get sent
        // after a timeout.
        if (Math.abs(this._accumulatedWheelDeltaX) > WHEEL_STEP) {
            this._generateWheelStepX();
        } else {
            this._wheelStepXTimer =
                window.setTimeout(this._generateWheelStepX.bind(this),
                                  WHEEL_STEP_TIMEOUT);
        }
        if (Math.abs(this._accumulatedWheelDeltaY) > WHEEL_STEP) {
            this._generateWheelStepY();
        } else {
            this._wheelStepYTimer =
                window.setTimeout(this._generateWheelStepY.bind(this),
                                  WHEEL_STEP_TIMEOUT);
        }

        stopEvent(e);
    }

    _handleMouseMove(e) {
        this._updateMousePosition(e);
        this.onmousemove(this._pos.x, this._pos.y);
        stopEvent(e);
    }

    _handleMouseDisable(e) {
        /*
         * Stop propagation if inside canvas area
         * Note: This is only needed for the 'click' event as it fails
         *       to fire properly for the target element so we have
         *       to listen on the document element instead.
         */
        if (e.target == this._target) {
            stopEvent(e);
        }
    }

    // Update coordinates relative to target
    _updateMousePosition(e) {
        e = getPointerEvent(e);
        const bounds = this._target.getBoundingClientRect();
        let x;
        let y;
        // Clip to target bounds
        if (e.clientX < bounds.left) {
            x = 0;
        } else if (e.clientX >= bounds.right) {
            x = bounds.width - 1;
        } else {
            x = e.clientX - bounds.left;
        }
        if (e.clientY < bounds.top) {
            y = 0;
        } else if (e.clientY >= bounds.bottom) {
            y = bounds.height - 1;
        } else {
            y = e.clientY - bounds.top;
        }
        this._pos = {x: x, y: y};
    }

    // ===== PUBLIC METHODS =====

    grab() {
        if (isTouchDevice) {
            this._target.addEventListener('touchstart', this._eventHandlers.mousedown);
            this._target.addEventListener('touchend', this._eventHandlers.mouseup);
            this._target.addEventListener('touchmove', this._eventHandlers.mousemove);
        }
        this._target.addEventListener('mousedown', this._eventHandlers.mousedown);
        this._target.addEventListener('mouseup', this._eventHandlers.mouseup);
        this._target.addEventListener('mousemove', this._eventHandlers.mousemove);
        this._target.addEventListener('wheel', this._eventHandlers.mousewheel);

        /* Prevent middle-click pasting (see above for why we bind to document) */
        document.addEventListener('click', this._eventHandlers.mousedisable);

        /* preventDefault() on mousedown doesn't stop this event for some
           reason so we have to explicitly block it */
        this._target.addEventListener('contextmenu', this._eventHandlers.mousedisable);
    }

    ungrab() {
        this._resetWheelStepTimers();

        if (isTouchDevice) {
            this._target.removeEventListener('touchstart', this._eventHandlers.mousedown);
            this._target.removeEventListener('touchend', this._eventHandlers.mouseup);
            this._target.removeEventListener('touchmove', this._eventHandlers.mousemove);
        }
        this._target.removeEventListener('mousedown', this._eventHandlers.mousedown);
        this._target.removeEventListener('mouseup', this._eventHandlers.mouseup);
        this._target.removeEventListener('mousemove', this._eventHandlers.mousemove);
        this._target.removeEventListener('wheel', this._eventHandlers.mousewheel);

        document.removeEventListener('click', this._eventHandlers.mousedisable);

        this._target.removeEventListener('contextmenu', this._eventHandlers.mousedisable);
    }
}