Author: kpreisser
Date: Tue Oct 29 18:54:05 2013
New Revision: 1536848
URL: http://svn.apache.org/r1536848
Log:
Add a description of to the Drawboard page.
Modified:
tomcat/trunk/webapps/examples/websocket/drawboard.xhtml
Modified: tomcat/trunk/webapps/examples/websocket/drawboard.xhtml
URL:
http://svn.apache.org/viewvc/tomcat/trunk/webapps/examples/websocket/drawboard.xhtml?rev=1536848&r1=1536847&r2=1536848&view=diff
==============================================================================
--- tomcat/trunk/webapps/examples/websocket/drawboard.xhtml (original)
+++ tomcat/trunk/webapps/examples/websocket/drawboard.xhtml Tue Oct 29 18:54:05
2013
@@ -82,6 +82,45 @@
noscripts[i].parentNode.removeChild(noscripts[i]);
}
+ // Add script for expand content.
+ var expandElements = document.getElementsByClassName("expand");
+ for (var ixx = 0; ixx < expandElements.length; ixx++) {
+ (function(el) {
+ var expandContent =
document.getElementById(el.getAttribute("data-content-id"));
+ expandContent.style.display = "none";
+ var arrow = document.createTextNode("⢠");
+ var arrowSpan = document.createElement("span");
+ arrowSpan.appendChild(arrow);
+
+ var link = document.createElement("a");
+ link.setAttribute("href", "#!");
+ while (el.firstChild != null) {
+ link.appendChild(el.removeChild(el.firstChild));
+ }
+ el.appendChild(arrowSpan);
+ el.appendChild(link);
+
+ var textSpan = document.createElement("span");
+ textSpan.setAttribute("style", "font-weight: normal;");
+ textSpan.appendChild(document.createTextNode(" (click to
expand)"));
+ el.appendChild(textSpan);
+
+
+ var visible = true;
+
+ var switchExpand = function() {
+ visible = !visible;
+ expandContent.style.display = visible ? "block" :
"none";
+ arrowSpan.style.color = visible ? "#000" : "#888";
+ return false;
+ };
+
+ link.onclick = switchExpand;
+ switchExpand();
+
+ })(expandElements[ixx]);
+ }
+
var Console = {};
@@ -812,11 +851,42 @@
]]></script>
</head>
<body>
- <div class="noscript"><h2 style="color: #ff0000;">Seems your browser
doesn't support Javascript! Websockets rely on Javascript being enabled. Please
enable
- Javascript and reload this page!</h2></div>
+ <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 Drawbord 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 (this needs NIO or APR connector
to be used).<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
â 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>
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