init repo
This commit is contained in:
nikolay ivanov
190
OfficeWeb/sdk/Common/Charts/docs/what-is-html5-canvas.html
Normal file
190
OfficeWeb/sdk/Common/Charts/docs/what-is-html5-canvas.html
Normal file
@@ -0,0 +1,190 @@
|
||||
<!DOCTYPE html>
|
||||
<html>
|
||||
<head>
|
||||
<meta http-equiv="X-UA-Compatible" content="chrome=1">
|
||||
<!--
|
||||
/**
|
||||
* o------------------------------------------------------------------------------o
|
||||
* | This file is part of the OfficeExcel package - you can learn more at: |
|
||||
* | |
|
||||
* | http://www.OfficeExcel.net |
|
||||
* | |
|
||||
* | This package is licensed under the OfficeExcel license. For all kinds of business |
|
||||
* | purposes there is a small one-time licensing fee to pay and for non |
|
||||
* | commercial purposes it is free to use. You can read the full license here: |
|
||||
* | |
|
||||
* | http://www.OfficeExcel.net/LICENSE.txt |
|
||||
* o------------------------------------------------------------------------------o
|
||||
*/
|
||||
-->
|
||||
<title>A short description of what HTML5 canvas is</title>
|
||||
|
||||
<meta name="keywords" content="OfficeExcel html5 canvas charts what " />
|
||||
<meta name="description" content="A short description of the HTML5 canvas tag" />
|
||||
<meta name="googlebot" content="NOODP">
|
||||
|
||||
<meta property="og:title" content="OfficeExcel: What is HTML5 canvas?" />
|
||||
<meta property="og:description" content="A brief description and a few examples of HTML5 canvas " />
|
||||
<meta property="og:image" content="http://www.OfficeExcel.net/images/logo.png"/>
|
||||
|
||||
<link rel="stylesheet" href="../css/website.css" type="text/css" media="screen" />
|
||||
<link rel="icon" type="image/png" href="../images/favicon.png">
|
||||
|
||||
<!-- Place this tag in your head or just before your close body tag -->
|
||||
<script type="text/javascript" src="https://apis.google.com/js/plusone.js"></script>
|
||||
|
||||
<script src="../libraries/OfficeExcel.common.core.js" ></script>
|
||||
<script src="../libraries/OfficeExcel.common.tooltips.js" ></script>
|
||||
<script src="../libraries/OfficeExcel.bar.js" ></script>
|
||||
|
||||
<!--[if lt IE 9]><script src="../excanvas/excanvas.original.js"></script><![endif]-->
|
||||
|
||||
|
||||
<?php PrintAnalyticsCode() ?>
|
||||
</head>
|
||||
|
||||
<body>
|
||||
|
||||
|
||||
<!-- Social networking buttons -->
|
||||
<?php
|
||||
$prefix = substr($_SERVER['SERVER_NAME'], 0, 3);
|
||||
require("/OfficeExcel.{$prefix}/social.html");
|
||||
?>
|
||||
<!-- Social networking buttons -->
|
||||
|
||||
<div id="breadcrumb">
|
||||
<a href="../index.html">OfficeExcel: HTML5 Javascript charts library</a>
|
||||
>
|
||||
<a href="./index.html">Documentation</a>
|
||||
>
|
||||
What is HTML5 canvas?
|
||||
</div>
|
||||
|
||||
<h1>What <span>is HTML5 canvas?</span></h1>
|
||||
|
||||
<script>
|
||||
if (OfficeExcel.isOld()) {
|
||||
document.write('<div style="background-color: #fee; border: 2px dashed red; padding: 5px"><b>Important</b><br /><br /> Internet Explorer does not natively support the HTML5 canvas tag, so if you want to see the charts, you can either:<ul><li>Install <a href="http://code.google.com/chrome/chromeframe/">Google Chrome Frame</a></li><li>Use ExCanvas. This is provided in the OfficeExcel Archive.</li><li>Use another browser entirely. Your choices are Firefox 3.5+, Chrome 2+, Safari 4+ or Opera 10.5+. </li></ul> <b>Note:</b> Internet Explorer 9 fully supports the canvas tag.</div>');
|
||||
}
|
||||
</script>
|
||||
|
||||
<ul>
|
||||
<li><a href="#introduction">Introduction</a></li>
|
||||
<li><a href="#history">History</a></li>
|
||||
<li><a href="#example">Example</a></li>
|
||||
<li><a href="#compare">Canvas compared to SVG</a></li>
|
||||
<li><a href="#support">Browser support for HTML5 canvas</a></li>
|
||||
</ul>
|
||||
|
||||
<a name="introduction"></a>
|
||||
<h2>Introduction</h2>
|
||||
|
||||
<p>
|
||||
HTML5 canvas is a new HTML tag (<i><canvas></i>) which is part of the forthcoming HTML5 standard. It allows bitmap
|
||||
drawing which is controlled using Javascript, and is what the OfficeExcel libraries use to draw the charts. You could
|
||||
liken it to a piece of paper which is part of your HTML page, on to which you can draw. Because you use Javascript to
|
||||
draw on the canvas it becomes part of your page and allows interaction very easily.
|
||||
</p>
|
||||
|
||||
<p>
|
||||
Canvas uses a "fire and forget" drawing methodology - there is no DOM that is maintained, so if you want to alter something
|
||||
you will probably have to redraw the entire canvas. The lack of a DOM means that canvas is fast to draw on and very
|
||||
responsive - important when you're providing iteractive charts to your users.
|
||||
</p>
|
||||
|
||||
<a name="history"></a>
|
||||
<h2>History</h2>
|
||||
<p>
|
||||
HTML5 canvas was originally introduced by Apple for use in WebKit (which is used in their Safari browser and Google Chrome).
|
||||
It is now part of the HTML5 specification and supported by all modern web browsers.
|
||||
</p>
|
||||
|
||||
<a name="example"></a>
|
||||
<h2>Example</h2>
|
||||
|
||||
<canvas id="cvs" width="350" height="250" style="border: 1px dashed gray; float: right">[No canvas support]</canvas>
|
||||
<script>
|
||||
window.onload = function ()
|
||||
{
|
||||
canvas = document.getElementById("cvs");
|
||||
context = canvas.getContext('2d');
|
||||
|
||||
// Draw the red triangle
|
||||
context.beginPath();
|
||||
context.strokeStyle = 'black';
|
||||
context.fillStyle = 'red';
|
||||
context.moveTo(100, 25);
|
||||
context.lineTo(150, 100);
|
||||
context.lineTo(50, 100);
|
||||
context.lineTo(100, 25);
|
||||
context.stroke();
|
||||
context.fill();
|
||||
|
||||
// Draw the blue square
|
||||
context.beginPath();
|
||||
context.fillStyle = 'rgba(0,0,255,0.5)';
|
||||
context.strokeRect(100, 75, 100,100);
|
||||
context.fillRect(100, 75, 100,100);
|
||||
context.stroke();
|
||||
context.fill();
|
||||
|
||||
// Draw the yellow circle
|
||||
context.beginPath();
|
||||
context.globalAlpha = 0.5;
|
||||
context.fillStyle = 'yellow';
|
||||
context.arc(200,175,50,0,2 * Math.PI, 0);
|
||||
context.stroke();
|
||||
context.fill();
|
||||
}
|
||||
</script>
|
||||
|
||||
<p>
|
||||
The example to the right is a very simple case of drawing a few primitives on the canvas. The dotted border is
|
||||
provided by CSS to illustrate the drawing area.
|
||||
</p>
|
||||
|
||||
<p>
|
||||
The <canvas> tag itself is defined with just a width/height/id attribute. The one here also has a style attribute
|
||||
to make it more evident in the page. The HTML used is shown below:
|
||||
</p>
|
||||
|
||||
<br clear="all" />
|
||||
|
||||
<pre class="code">
|
||||
<canvas id="cvs" width="375" height="250">[No canvas support]<canvas>
|
||||
</pre>
|
||||
|
||||
The content in between the tags is not shown if the browser supports canvas, and is if the browser doesn't. This provides
|
||||
for fallback content if the users browser doesn't support canvas.
|
||||
|
||||
<a name="compare"></a>
|
||||
<h2>HTML5 Canvas compared to SVG</h2>
|
||||
<p>
|
||||
HTML5 canvas can be compared (a bit) to SVG - which is a vector based alternative for drawing in HTML pages. SVG is
|
||||
at a more abstract level than canvas and maintains a record of everything drawn, using a DOM. This is then converted
|
||||
to a bitmap when shown. In the above example, if the blue squares coordinates are changed (eg in an animation),
|
||||
then the whole canvas needs to be cleared and redrawn for each frame of that animation.
|
||||
</p>
|
||||
|
||||
<p>
|
||||
As a result of not having to maintain a DOM though, <canvas> is fast to draw on and display to the browser.
|
||||
</p>
|
||||
|
||||
<a name="support"></a>
|
||||
<h2>Browser support for HTML5 canvas</h2>
|
||||
<p>
|
||||
Modern browsers supporting HTML5 support canvas, including IE9+. Earlier versions of MSIE have some support through
|
||||
compatibility layers provided by Google and Mozilla. One such library - ExCanvas - is provided in the OfficeExcel archive
|
||||
allowing IE7 and 8 to display the graphs, albeit without many of the dynamic features. You can read more on this
|
||||
<a href="msie.html">here</a>.
|
||||
</p>
|
||||
|
||||
<p align="right">
|
||||
<b>
|
||||
<a href="index.html">Full documentation »</a>
|
||||
</b>
|
||||
</p>
|
||||
|
||||
</body>
|
||||
</html>
|
||||
Reference in New Issue
Block a user