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| author | Yves Fischer <yvesf-git@xapek.org> | 2011-10-23 21:14:40 +0200 |
|---|---|---|
| committer | Yves Fischer <yvesf-git@xapek.org> | 2011-10-30 11:33:54 +0100 |
| commit | 770ba5201f5c60b2bb36602ff9d359f641e33125 (patch) | |
| tree | 2200757f04efbc281c4b3714bfe2e4fe911193b6 /schall/static/RGraph/docs/what-is-html5-canvas.html | |
| parent | 77f5e686612898974e13f2a5df57c20e4e529363 (diff) | |
| download | mini-octopus-770ba5201f5c60b2bb36602ff9d359f641e33125.tar.gz mini-octopus-770ba5201f5c60b2bb36602ff9d359f641e33125.zip | |
Charting with flask, rgraph and custom "timeseries database"
Diffstat (limited to 'schall/static/RGraph/docs/what-is-html5-canvas.html')
| -rw-r--r-- | schall/static/RGraph/docs/what-is-html5-canvas.html | 207 |
1 files changed, 207 insertions, 0 deletions
diff --git a/schall/static/RGraph/docs/what-is-html5-canvas.html b/schall/static/RGraph/docs/what-is-html5-canvas.html new file mode 100644 index 0000000..bfce4ac --- /dev/null +++ b/schall/static/RGraph/docs/what-is-html5-canvas.html @@ -0,0 +1,207 @@ +<!DOCTYPE html> +<html> +<head> + <meta http-equiv="X-UA-Compatible" content="chrome=1"> + <!-- + /** + * o------------------------------------------------------------------------------o + * | This file is part of the RGraph package - you can learn more at: | + * | | + * | http://www.rgraph.net | + * | | + * | This package is licensed under the RGraph 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.rgraph.net/LICENSE.txt | + * o------------------------------------------------------------------------------o + */ + --> + <title>RGraph: What is HTML5 canvas?</title> + + <meta name="keywords" content="rgraph html5 canvas charts what " /> + <meta name="description" content="RGraph: What is HTML5 canvas?" /> + + <meta property="og:title" content="RGraph: 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.rgraph.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/RGraph.common.core.js" ></script> + <script src="../libraries/RGraph.common.tooltips.js" ></script> + <script src="../libraries/RGraph.bar.js" ></script> + + + <script> + var _gaq = _gaq || []; + _gaq.push(['_setAccount', 'UA-54706-2']); + _gaq.push(['_trackPageview']); + + (function() { + var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; + ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; + var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); + })(); + </script> +</head> + +<body> + + + <!-- Social networking buttons --> + <div id="social_icons" class="warning" style="border-radius: 10px; top: 1px; position: fixed; width: 120px; height: 20px"> + <!-- <a title="Bookmark with delicious" href="http://delicious.com/save?jump=close&v=4&noui&jump=close&url=http://www.rgraph.net¬es=RGraph%20is%20a%20HTML5%20based%20javascript%20charts%20library%20supporting%20a%20wide%20range%20of%20different%20chart%20types&title=RGraph:%20Javascript%20charts%20%26%20graph%20library" target="_blank"><img src="../images/delicious.png" alt="Bookmark with delicious" width="22" height="22" border="0" style="position: relative; top: 1px" /></a> --> + <a href="http://twitter.com/home/?status=RGraph%3A%20Javascript+charts+library+http%3A%2F%2Fwww.rgraph.net+%23rgraph+%23html5+%23canvas+%23javascript+%23charts+@_rgraph" target="_blank" title="Mention RGraph on Twitter"><img src="../images/twitter.png" alt="Mention RGraph on Twitter"/></a> + <iframe src="http://www.facebook.com/plugins/like.php?app_id=253862424642173&href=http%3A%2F%2Fwww.rgraph.net&send=false&layout=button_count&width=450&show_faces=false&action=like&colorscheme=light&font=arial&height=21" scrolling="no" frameborder="0" style="width: 80px; height:21px; position: relative; top: 1px"></iframe> + </div> + + <script> + // Opera fix + if (navigator.userAgent.indexOf('Opera') == -1) { + document.getElementById("social_icons").style.position = 'fixed'; + } + </script> + + <div id="google_plusone"> + <!-- Place this tag where you want the +1 button to render --> + <g:plusone href="http://www.rgraph.net"></g:plusone> + </div> + <!-- Social networking buttons --> + + <div id="breadcrumb"> + <a href="../index.html">RGraph: HTML5 Javascript charts library</a> + > + <a href="index.html">Documentation</a> + > + What is HTML5 canvas? + </div> + + <h1>RGraph: <span>HTML5 Javascript charts library</span> - What is HTML5 canvas?</h1> + + <script> + if (RGraph.isIE8()) { + document.write('<div style="background-color: #fee; border: 2px dashed red; padding: 5px"><b>Important</b><br /><br /> Internet Explorer 8 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 RGraph 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 RGraph 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 the majority (if not all) of 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> + 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. + </p> + + <p> + As a result of not having to maintain a DOM <canvas> is fast to draw on and display to the browser. + </p> + + <a name="support"></a> + <h2>Browser support for HTML5 canvas</h2> + <p> + The majority of current browsers 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 RGraph archive + allowing IE8 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>
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