<?xml version="1.0" encoding="UTF-8"?>
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<!--
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Licensed to the Apache Software Foundation (ASF) under one or more
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contributor license agreements. See the NOTICE file distributed with
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this work for additional information regarding copyright ownership.
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The ASF licenses this file to You under the Apache License, Version 2.0
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(the "License"); you may not use this file except in compliance with
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the License. You may obtain a copy of the License at
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|
http://www.apache.org/licenses/LICENSE-2.0
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|
Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
|
limitations under the License.
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-->
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<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
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<head>
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<title>Apache Tomcat WebSocket Examples: Drawboard</title>
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<style type="text/css"><![CDATA[
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body {
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font-family: Arial, sans-serif;
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font-size: 11pt;
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background-color: #eeeeea;
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padding: 10px;
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}
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#console-container {
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float: left;
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background-color: #fff;
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width: 250px;
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}
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#console {
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font-size: 10pt;
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height: 600px;
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overflow-y: scroll;
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padding-left: 5px;
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padding-right: 5px;
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}
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#console p {
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padding: 0;
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margin: 0;
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}
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#drawContainer {
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float: left;
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display: none;
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margin-right: 25px;
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}
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#drawContainer canvas {
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display: block;
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-ms-touch-action: none;
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touch-action: none; /* Disable touch behaviors, like pan and zoom */
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cursor: crosshair;
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}
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#labelContainer {
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margin-bottom: 15px;
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}
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#drawContainer, #console-container {
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box-shadow: 0px 0px 8px 3px #bbb;
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border: 1px solid #CCCCCC;
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}
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]]></style>
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<script type="application/javascript"><![CDATA[
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"use strict";
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(function() {
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document.addEventListener("DOMContentLoaded", function() {
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// Remove elements with "noscript" class - <noscript> is not
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// allowed in XHTML
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var noscripts = document.getElementsByClassName("noscript");
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for (var i = 0; i < noscripts.length; i++) {
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noscripts[i].parentNode.removeChild(noscripts[i]);
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}
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|
// Add script for expand content.
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var expandElements = document.getElementsByClassName("expand");
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for (var ixx = 0; ixx < expandElements.length; ixx++) {
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(function(el) {
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var expandContent = document.getElementById(el.getAttribute("data-content-id"));
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expandContent.style.display = "none";
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var arrow = document.createTextNode("◢ ");
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var arrowSpan = document.createElement("span");
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arrowSpan.appendChild(arrow);
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var link = document.createElement("a");
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link.setAttribute("href", "#!");
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while (el.firstChild != null) {
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link.appendChild(el.removeChild(el.firstChild));
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}
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el.appendChild(arrowSpan);
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el.appendChild(link);
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var textSpan = document.createElement("span");
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textSpan.setAttribute("style", "font-weight: normal;");
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textSpan.appendChild(document.createTextNode(" (click to expand)"));
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el.appendChild(textSpan);
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|
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var visible = true;
|
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var switchExpand = function() {
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visible = !visible;
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expandContent.style.display = visible ? "block" : "none";
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arrowSpan.style.color = visible ? "#000" : "#888";
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return false;
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};
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link.onclick = switchExpand;
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switchExpand();
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|
})(expandElements[ixx]);
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}
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|
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var Console = {};
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Console.log = (function() {
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var consoleContainer =
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document.getElementById("console-container");
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var console = document.createElement("div");
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console.setAttribute("id", "console");
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consoleContainer.appendChild(console);
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return function(message) {
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var p = document.createElement('p');
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p.style.wordWrap = "break-word";
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p.appendChild(document.createTextNode(message));
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console.appendChild(p);
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while (console.childNodes.length > 25) {
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console.removeChild(console.firstChild);
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}
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console.scrollTop = console.scrollHeight;
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}
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})();
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|
|
function Room(drawContainer) {
|
|
/* A pausable event forwarder that can be used to pause and
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* resume handling of events (e.g. when we need to wait
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* for a Image's load event before we can process further
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* WebSocket messages).
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* The object's callFunction(func) should be called from an
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* event handler and give the function to handle the event as
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* argument.
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* Call pauseProcessing() to suspend event forwarding and
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* resumeProcessing() to resume it.
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*/
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function PausableEventForwarder() {
|
|
var pauseProcessing = false;
|
// Queue for buffering functions to be called.
|
var functionQueue = [];
|
|
this.callFunction = function(func) {
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// If message processing is paused, we push it
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// into the queue - otherwise we process it directly.
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if (pauseProcessing) {
|
functionQueue.push(func);
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} else {
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func();
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}
|
};
|
|
this.pauseProcessing = function() {
|
pauseProcessing = true;
|
};
|
|
this.resumeProcessing = function() {
|
pauseProcessing = false;
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|
// Process all queued functions until some handler calls
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// pauseProcessing() again.
|
while (functionQueue.length > 0 && !pauseProcessing) {
|
var func = functionQueue.pop();
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func();
|
}
|
};
|
}
|
|
// The WebSocket object.
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var socket;
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// ID of the timer which sends ping messages.
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var pingTimerId;
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var isStarted = false;
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var playerCount = 0;
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|
// An array of PathIdContainer objects that the server
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// did not yet handle.
|
// They are ordered by id (ascending).
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var pathsNotHandled = [];
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var nextMsgId = 1;
|
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var canvasDisplay = document.createElement("canvas");
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var canvasBackground = document.createElement("canvas");
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var canvasServerImage = document.createElement("canvas");
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var canvasArray = [canvasDisplay, canvasBackground,
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canvasServerImage];
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canvasDisplay.addEventListener("mousedown", function(e) {
|
// Prevent default mouse event to prevent browsers from marking text
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// (and Chrome from displaying the "text" cursor).
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e.preventDefault();
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}, false);
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var labelPlayerCount = document.createTextNode("0");
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var optionContainer = document.createElement("div");
|
|
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var canvasDisplayCtx = canvasDisplay.getContext("2d");
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var canvasBackgroundCtx = canvasBackground.getContext("2d");
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var canvasServerImageCtx = canvasServerImage.getContext("2d");
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var canvasMouseMoveHandler;
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var canvasMouseDownHandler;
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|
var isActive = false;
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var mouseInWindow = false;
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var mouseDown = false;
|
var currentMouseX = 0, currentMouseY = 0;
|
var currentPreviewPath = null;
|
|
var availableColors = [];
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var currentColorIndex;
|
var colorContainers;
|
var previewTransparency = 0.65;
|
|
var availableThicknesses = [2, 3, 6, 10, 16, 28, 50];
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var currentThicknessIndex;
|
var thicknessContainers;
|
|
var availableDrawTypes = [
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{ name: "Brush", id: 1, continuous: true },
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{ name: "Line", id: 2, continuous: false },
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{ name: "Rectangle", id: 3, continuous: false },
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{ name: "Ellipse", id: 4, continuous: false }
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];
|
var currentDrawTypeIndex;
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var drawTypeContainers;
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|
|
var labelContainer = document.getElementById("labelContainer");
|
var placeholder = document.createElement("div");
|
placeholder.appendChild(document.createTextNode("Loading... "));
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var progressElem = document.createElement("progress");
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placeholder.appendChild(progressElem);
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labelContainer.appendChild(placeholder);
|
|
function rgb(color) {
|
return "rgba(" + color[0] + "," + color[1] + ","
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+ color[2] + "," + color[3] + ")";
|
}
|
|
function PathIdContainer(path, id) {
|
this.path = path;
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this.id = id;
|
}
|
|
function Path(type, color, thickness, x1, y1, x2, y2) {
|
this.type = type;
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this.color = color;
|
this.thickness = thickness;
|
this.x1 = x1;
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this.y1 = y1;
|
this.x2 = x2;
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this.y2 = y2;
|
|
function ellipse(ctx, x, y, w, h) {
|
/* Drawing a ellipse cannot be done directly in a
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* CanvasRenderingContext2D - we need to use drawArc()
|
* in conjunction with scaling the context so that we
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* get the needed proportion.
|
*/
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ctx.save();
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|
// Translate and scale the context so that we can draw
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// an arc at (0, 0) with a radius of 1.
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ctx.translate(x + w / 2, y + h / 2);
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ctx.scale(w / 2, h / 2);
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|
ctx.beginPath();
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ctx.arc(0, 0, 1, 0, Math.PI * 2, false);
|
|
ctx.restore();
|
}
|
|
this.draw = function(ctx) {
|
ctx.beginPath();
|
ctx.lineCap = "round";
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ctx.lineWidth = thickness;
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var style = rgb(color);
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ctx.strokeStyle = style;
|
|
if (x1 == x2 && y1 == y2) {
|
// Always draw as arc to meet the behavior
|
// in Java2D.
|
ctx.fillStyle = style;
|
ctx.arc(x1, y1, thickness / 2.0, 0,
|
Math.PI * 2.0, false);
|
ctx.fill();
|
} else {
|
if (type == 1 || type == 2) {
|
// Draw a line.
|
ctx.moveTo(x1, y1);
|
ctx.lineTo(x2, y2);
|
ctx.stroke();
|
} else if (type == 3) {
|
// Draw a rectangle.
|
if (x1 == x2 || y1 == y2) {
|
// Draw as line
|
ctx.moveTo(x1, y1);
|
ctx.lineTo(x2, y2);
|
ctx.stroke();
|
} else {
|
ctx.strokeRect(x1, y1, x2 - x1, y2 - y1);
|
}
|
} else if (type == 4) {
|
// Draw a ellipse.
|
ellipse(ctx, x1, y1, x2 - x1, y2 - y1);
|
ctx.closePath();
|
ctx.stroke();
|
}
|
}
|
};
|
}
|
|
|
function connect() {
|
var host = (window.location.protocol == "https:"
|
? "wss://" : "ws://") + window.location.host
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+ "/examples/websocket/drawboard";
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socket = new WebSocket(host);
|
|
/* Use a pausable event forwarder.
|
* This is needed when we load an Image object with data
|
* from a previous message, because we must wait until the
|
* Image's load event it raised before we can use it (and
|
* in the meantime the socket.message event could be
|
* raised).
|
* Therefore we need this pausable event handler to handle
|
* e.g. socket.onmessage and socket.onclose.
|
*/
|
var eventForwarder = new PausableEventForwarder();
|
|
socket.onopen = function () {
|
// Socket has opened. Now wait for the server to
|
// send us the initial packet.
|
Console.log("WebSocket connection opened.");
|
|
// Set up a timer for pong messages.
|
pingTimerId = window.setInterval(function() {
|
socket.send("0");
|
}, 30000);
|
};
|
|
socket.onclose = function () {
|
eventForwarder.callFunction(function() {
|
Console.log("WebSocket connection closed.");
|
disableControls();
|
|
// Disable pong timer.
|
window.clearInterval(pingTimerId);
|
});
|
};
|
|
// Handles an incoming Websocket message.
|
var handleOnMessage = function(message) {
|
|
// Split joined message and process them
|
// individually.
|
var messages = message.data.split(";");
|
for (var msgArrIdx = 0; msgArrIdx < messages.length;
|
msgArrIdx++) {
|
var msg = messages[msgArrIdx];
|
var type = msg.substring(0, 1);
|
|
if (type == "0") {
|
// Error message.
|
var error = msg.substring(1);
|
// Log it to the console and show an alert.
|
Console.log("Error: " + error);
|
alert(error);
|
|
} else {
|
if (!isStarted) {
|
if (type == "2") {
|
// Initial message. It contains the
|
// number of players.
|
// After this message we will receive
|
// a binary message containing the current
|
// room image as PNG.
|
playerCount = parseInt(msg.substring(1));
|
|
refreshPlayerCount();
|
|
// The next message will be a binary
|
// message containing the room images
|
// as PNG. Therefore we temporarily swap
|
// the message handler.
|
var originalHandler = handleOnMessage;
|
handleOnMessage = function(message) {
|
// First, we restore the original handler.
|
handleOnMessage = originalHandler;
|
|
// Read the image.
|
var blob = message.data;
|
// Create new blob with correct MIME type.
|
blob = new Blob([blob], {type : "image/png"});
|
|
var url = URL.createObjectURL(blob);
|
|
var img = new Image();
|
|
// We must wait until the onload event is
|
// raised until we can draw the image onto
|
// the canvas.
|
// Therefore we need to pause the event
|
// forwarder until the image is loaded.
|
eventForwarder.pauseProcessing();
|
|
img.onload = function() {
|
|
// Release the object URL.
|
URL.revokeObjectURL(url);
|
|
// Set the canvases to the correct size.
|
for (var i = 0; i < canvasArray.length; i++) {
|
canvasArray[i].width = img.width;
|
canvasArray[i].height = img.height;
|
}
|
|
// Now draw the image on the last canvas.
|
canvasServerImageCtx.clearRect(0, 0,
|
canvasServerImage.width,
|
canvasServerImage.height);
|
canvasServerImageCtx.drawImage(img, 0, 0);
|
|
// Draw it on the background canvas.
|
canvasBackgroundCtx.drawImage(canvasServerImage,
|
0, 0);
|
|
isStarted = true;
|
startControls();
|
|
// Refresh the display canvas.
|
refreshDisplayCanvas();
|
|
|
// Finally, resume the event forwarder.
|
eventForwarder.resumeProcessing();
|
};
|
|
img.src = url;
|
};
|
}
|
} else {
|
if (type == "3") {
|
// The number of players in this room changed.
|
var playerAdded = msg.substring(1) == "+";
|
playerCount += playerAdded ? 1 : -1;
|
refreshPlayerCount();
|
|
Console.log("Player " + (playerAdded
|
? "joined." : "left."));
|
|
} else if (type == "1") {
|
// We received a new DrawMessage.
|
var maxLastHandledId = -1;
|
var drawMessages = msg.substring(1).split("|");
|
for (var i = 0; i < drawMessages.length; i++) {
|
var elements = drawMessages[i].split(",");
|
var lastHandledId = parseInt(elements[0]);
|
maxLastHandledId = Math.max(maxLastHandledId,
|
lastHandledId);
|
|
var path = new Path(
|
parseInt(elements[1]),
|
[parseInt(elements[2]),
|
parseInt(elements[3]),
|
parseInt(elements[4]),
|
parseInt(elements[5]) / 255.0],
|
parseFloat(elements[6]),
|
parseFloat(elements[7]),
|
parseFloat(elements[8]),
|
parseFloat(elements[9]),
|
parseFloat(elements[10]));
|
|
// Draw the path onto the last canvas.
|
path.draw(canvasServerImageCtx);
|
}
|
|
// Draw the last canvas onto the background one.
|
canvasBackgroundCtx.drawImage(canvasServerImage,
|
0, 0);
|
|
// Now go through the pathsNotHandled array and
|
// remove the paths that were already handled by
|
// the server.
|
while (pathsNotHandled.length > 0
|
&& pathsNotHandled[0].id <= maxLastHandledId)
|
pathsNotHandled.shift();
|
|
// Now me must draw the remaining paths onto
|
// the background canvas.
|
for (var i = 0; i < pathsNotHandled.length; i++) {
|
pathsNotHandled[i].path.draw(canvasBackgroundCtx);
|
}
|
|
refreshDisplayCanvas();
|
}
|
}
|
}
|
}
|
};
|
|
socket.onmessage = function(message) {
|
eventForwarder.callFunction(function() {
|
handleOnMessage(message);
|
});
|
};
|
|
}
|
|
|
function refreshPlayerCount() {
|
labelPlayerCount.nodeValue = String(playerCount);
|
}
|
|
function refreshDisplayCanvas() {
|
if (!isActive) { // Don't draw a curser when not active.
|
return;
|
}
|
|
canvasDisplayCtx.drawImage(canvasBackground, 0, 0);
|
if (currentPreviewPath != null) {
|
// Draw the preview path.
|
currentPreviewPath.draw(canvasDisplayCtx);
|
|
} else if (mouseInWindow && !mouseDown) {
|
canvasDisplayCtx.beginPath();
|
var color = availableColors[currentColorIndex].slice(0);
|
color[3] = previewTransparency;
|
canvasDisplayCtx.fillStyle = rgb(color);
|
|
canvasDisplayCtx.arc(currentMouseX, currentMouseY,
|
availableThicknesses[currentThicknessIndex] / 2,
|
0, Math.PI * 2.0, true);
|
canvasDisplayCtx.fill();
|
}
|
|
}
|
|
function startControls() {
|
isActive = true;
|
|
labelContainer.removeChild(placeholder);
|
placeholder = undefined;
|
|
labelContainer.appendChild(
|
document.createTextNode("Number of Players: "));
|
labelContainer.appendChild(labelPlayerCount);
|
|
|
drawContainer.style.display = "block";
|
drawContainer.appendChild(canvasDisplay);
|
|
drawContainer.appendChild(optionContainer);
|
|
canvasMouseDownHandler = function(e) {
|
if (e.button == 0) {
|
currentMouseX = e.pageX - canvasDisplay.offsetLeft;
|
currentMouseY = e.pageY - canvasDisplay.offsetTop;
|
|
mouseDown = true;
|
canvasMouseMoveHandler(e);
|
|
} else if (mouseDown) {
|
// Cancel drawing.
|
mouseDown = false;
|
currentPreviewPath = null;
|
|
currentMouseX = e.pageX - canvasDisplay.offsetLeft;
|
currentMouseY = e.pageY - canvasDisplay.offsetTop;
|
|
refreshDisplayCanvas();
|
}
|
};
|
canvasDisplay.addEventListener("mousedown", canvasMouseDownHandler, false);
|
|
canvasMouseMoveHandler = function(e) {
|
var mouseX = e.pageX - canvasDisplay.offsetLeft;
|
var mouseY = e.pageY - canvasDisplay.offsetTop;
|
|
if (mouseDown) {
|
var drawType = availableDrawTypes[currentDrawTypeIndex];
|
|
if (drawType.continuous) {
|
|
var path = new Path(drawType.id,
|
availableColors[currentColorIndex],
|
availableThicknesses[currentThicknessIndex],
|
currentMouseX, currentMouseY, mouseX,
|
mouseY);
|
// Draw it on the background canvas.
|
path.draw(canvasBackgroundCtx);
|
|
// Send it to the sever.
|
pushPath(path);
|
|
// Refresh old coordinates
|
currentMouseX = mouseX;
|
currentMouseY = mouseY;
|
|
} else {
|
// Create a new preview path.
|
var color = availableColors[currentColorIndex].slice(0);
|
color[3] = previewTransparency;
|
currentPreviewPath = new Path(drawType.id,
|
color,
|
availableThicknesses[currentThicknessIndex],
|
currentMouseX, currentMouseY, mouseX,
|
mouseY, false);
|
}
|
|
refreshDisplayCanvas();
|
} else {
|
currentMouseX = mouseX;
|
currentMouseY = mouseY;
|
|
if (mouseInWindow) {
|
refreshDisplayCanvas();
|
}
|
}
|
|
};
|
document.addEventListener("mousemove", canvasMouseMoveHandler, false);
|
|
document.addEventListener("mouseup", function(e) {
|
if (e.button == 0) {
|
if (mouseDown) {
|
mouseDown = false;
|
currentPreviewPath = null;
|
|
var mouseX = e.pageX - canvasDisplay.offsetLeft;
|
var mouseY = e.pageY - canvasDisplay.offsetTop;
|
var drawType = availableDrawTypes[currentDrawTypeIndex];
|
|
// If we are drawing a continuous path and the previous mouse coordinates are the same as
|
// the new ones, there is no need to construct a new draw message as we don't need to
|
// "terminate" a path as every path element contains both the start and the end point.
|
if (!(drawType.continuous && mouseX == currentMouseX && mouseY == currentMouseY)) {
|
var path = new Path(drawType.id, availableColors[currentColorIndex],
|
availableThicknesses[currentThicknessIndex],
|
currentMouseX, currentMouseY, mouseX,
|
mouseY);
|
// Draw it on the background canvas.
|
path.draw(canvasBackgroundCtx);
|
|
// Send it to the sever.
|
pushPath(path);
|
|
// Refresh old coordinates
|
currentMouseX = mouseX;
|
currentMouseY = mouseY;
|
}
|
|
refreshDisplayCanvas();
|
}
|
}
|
}, false);
|
|
canvasDisplay.addEventListener("mouseout", function(e) {
|
mouseInWindow = false;
|
refreshDisplayCanvas();
|
}, false);
|
|
canvasDisplay.addEventListener("mousemove", function(e) {
|
if (!mouseInWindow) {
|
mouseInWindow = true;
|
refreshDisplayCanvas();
|
}
|
}, false);
|
|
|
// Create color and thickness controls.
|
var colorContainersBox = document.createElement("div");
|
colorContainersBox.setAttribute("style",
|
"margin: 4px; border: 1px solid #bbb; border-radius: 3px;");
|
optionContainer.appendChild(colorContainersBox);
|
|
colorContainers = new Array(3 * 3 * 3);
|
for (var i = 0; i < colorContainers.length; i++) {
|
var colorContainer = colorContainers[i] =
|
document.createElement("div");
|
var color = availableColors[i] =
|
[
|
Math.floor((i % 3) * 255 / 2),
|
Math.floor((Math.floor(i / 3) % 3) * 255 / 2),
|
Math.floor((Math.floor(i / (3 * 3)) % 3) * 255 / 2),
|
1.0
|
];
|
colorContainer.setAttribute("style",
|
"margin: 3px; width: 18px; height: 18px; "
|
+ "float: left; background-color: " + rgb(color));
|
colorContainer.style.border = '2px solid #000';
|
colorContainer.addEventListener("mousedown", (function(ix) {
|
return function() {
|
setColor(ix);
|
};
|
})(i), false);
|
|
colorContainersBox.appendChild(colorContainer);
|
}
|
|
var divClearLeft = document.createElement("div");
|
divClearLeft.setAttribute("style", "clear: left;");
|
colorContainersBox.appendChild(divClearLeft);
|
|
|
var drawTypeContainersBox = document.createElement("div");
|
drawTypeContainersBox.setAttribute("style",
|
"float: right; margin-right: 3px; margin-top: 1px;");
|
optionContainer.appendChild(drawTypeContainersBox);
|
|
drawTypeContainers = new Array(availableDrawTypes.length);
|
for (var i = 0; i < drawTypeContainers.length; i++) {
|
var drawTypeContainer = drawTypeContainers[i] =
|
document.createElement("div");
|
drawTypeContainer.setAttribute("style",
|
"text-align: center; margin: 3px; padding: 0 3px;"
|
+ "height: 18px; float: left;");
|
drawTypeContainer.style.border = "2px solid #000";
|
drawTypeContainer.appendChild(document.createTextNode(
|
String(availableDrawTypes[i].name)));
|
drawTypeContainer.addEventListener("mousedown", (function(ix) {
|
return function() {
|
setDrawType(ix);
|
};
|
})(i), false);
|
|
drawTypeContainersBox.appendChild(drawTypeContainer);
|
}
|
|
|
var thicknessContainersBox = document.createElement("div");
|
thicknessContainersBox.setAttribute("style",
|
"margin: 3px; border: 1px solid #bbb; border-radius: 3px;");
|
optionContainer.appendChild(thicknessContainersBox);
|
|
thicknessContainers = new Array(availableThicknesses.length);
|
for (var i = 0; i < thicknessContainers.length; i++) {
|
var thicknessContainer = thicknessContainers[i] =
|
document.createElement("div");
|
thicknessContainer.setAttribute("style",
|
"text-align: center; margin: 3px; width: 18px; "
|
+ "height: 18px; float: left;");
|
thicknessContainer.style.border = "2px solid #000";
|
thicknessContainer.appendChild(document.createTextNode(
|
String(availableThicknesses[i])));
|
thicknessContainer.addEventListener("mousedown", (function(ix) {
|
return function() {
|
setThickness(ix);
|
};
|
})(i), false);
|
|
thicknessContainersBox.appendChild(thicknessContainer);
|
}
|
|
|
divClearLeft = document.createElement("div");
|
divClearLeft.setAttribute("style", "clear: left;");
|
thicknessContainersBox.appendChild(divClearLeft);
|
|
|
setColor(0);
|
setThickness(0);
|
setDrawType(0);
|
|
}
|
|
function disableControls() {
|
document.removeEventListener("mousedown", canvasMouseDownHandler);
|
document.removeEventListener("mousemove", canvasMouseMoveHandler);
|
mouseInWindow = false;
|
refreshDisplayCanvas();
|
|
isActive = false;
|
}
|
|
function pushPath(path) {
|
|
// Push it into the pathsNotHandled array.
|
var container = new PathIdContainer(path, nextMsgId++);
|
pathsNotHandled.push(container);
|
|
// Send the path to the server.
|
var message = container.id + "|" + path.type + ","
|
+ path.color[0] + "," + path.color[1] + ","
|
+ path.color[2] + ","
|
+ Math.round(path.color[3] * 255.0) + ","
|
+ path.thickness + "," + path.x1 + ","
|
+ path.y1 + "," + path.x2 + "," + path.y2;
|
|
socket.send("1" + message);
|
}
|
|
function setThickness(thicknessIndex) {
|
if (typeof currentThicknessIndex !== "undefined")
|
thicknessContainers[currentThicknessIndex]
|
.style.borderColor = "#000";
|
currentThicknessIndex = thicknessIndex;
|
thicknessContainers[currentThicknessIndex]
|
.style.borderColor = "#d08";
|
}
|
|
function setColor(colorIndex) {
|
if (typeof currentColorIndex !== "undefined")
|
colorContainers[currentColorIndex]
|
.style.borderColor = "#000";
|
currentColorIndex = colorIndex;
|
colorContainers[currentColorIndex]
|
.style.borderColor = "#d08";
|
}
|
|
function setDrawType(drawTypeIndex) {
|
if (typeof currentDrawTypeIndex !== "undefined")
|
drawTypeContainers[currentDrawTypeIndex]
|
.style.borderColor = "#000";
|
currentDrawTypeIndex = drawTypeIndex;
|
drawTypeContainers[currentDrawTypeIndex]
|
.style.borderColor = "#d08";
|
}
|
|
|
connect();
|
|
}
|
|
|
// Initialize the room
|
var room = new Room(document.getElementById("drawContainer"));
|
|
|
}, false);
|
|
})();
|
]]></script>
|
</head>
|
<body>
|
<div class="noscript"><div style="color: #ff0000; font-size: 16pt;">Seems your browser doesn't support JavaScript! Websockets rely on JavaScript being enabled. Please enable
|
JavaScript and reload this page!</div></div>
|
<div id="labelContainer"/>
|
<div id="drawContainer"/>
|
<div id="console-container"/>
|
<div style="clear: left;"/>
|
|
<h1 class="expand" data-content-id="expandContent" style="font-size: 1.3em;"
|
>About Drawboard WebSocket Example</h1>
|
<div id="expandContent">
|
<p>
|
This drawboard is a page where you can draw with your mouse or touch input
|
(using different colors) and everybody else which has the page open will
|
<em>immediately</em> see what you are drawing.<br/>
|
If someone opens the page later, they will get the current room image (so they
|
can see what was already drawn by other people).
|
</p>
|
<p>
|
It uses asynchronous sending of messages so that it doesn't need separate threads
|
for each client to send messages.<br/>
|
Each "Room" (where the drawing happens) uses a ReentrantLock to synchronize access
|
(currently, only a single Room is implemented).
|
</p>
|
<p>
|
When you open the page, first you will receive a binary websocket message containing
|
the current room image as PNG image. After that, you will receive string messages
|
that contain the drawing actions (line from x1,y1 to x2,y2).<br/>
|
<small>Note that it currently only uses simple string messages instead of JSON because
|
I did not want to introduce a dependency on a JSON lib.</small>
|
</p>
|
<p>
|
It uses synchronization mechanisms to ensure that the final image will look the same
|
for every user, regardless of what their network latency/speed is – e.g. if two user
|
draw at the same time on the same place, the server will decide which line was the
|
first one, and that will be reflected on every client.
|
</p>
|
</div>
|
</body>
|
</html>
|
