Showing posts with label HTML5. Show all posts
Showing posts with label HTML5. Show all posts

Monday, May 13, 2013

Escaping the HTML5 sandbox with Qt

HTML5 has a large number of powerful APIs that make it a candidate for cross-platform development of rich desktop-type apps. One last missing piece stands in the way: unfettered access to the local filesystem: local files, thumb drives, and network shares. Perhaps someday there will be a facility to "sign" HTML5 apps to allow them access to the local filesystem, but it is not the case today.

Qt is a stopgap measure to allow you to keep 98% of your app code in HTML5, where the other 2% is Qt C++ to access the local filesystem. This preserves cross-platform capacity and potential, including to the cloud. (In contrast, a conventional Qt app without HTML5 would not be able to be hosted on the cloud.)

Below are the slides from the presentation I gave on May 13, 2013 at the Denver HTML5 Meetup group. And below that is a YouTube with audio narration, recreating the presentation.

Posted by at No comments:
Labels:

Sunday, October 21, 2012

XML/XSL/HTML5 for reports instead of PDF

Since video of my actual presentation to the Denver HTML5 Meetup on October 22, 2012 won't be posted for a few more months, I quickly recorded the 10-minute YouTube below.


Below are the slides.

XML/XSL/HTML5 for reports instead of PDF



The official w3.org documentation on embedding XSL in XML actually dates from circa 2000.  Firefox still allows it.  Here is the overall structure of the .XML file:

<?xml version="1.0" encoding="ISO-8859-1"?>
<?xml-stylesheet type="text/xsl" href="#stylesheet"?>
<!DOCTYPE doc [
<!ATTLIST xsl:stylesheet
id ID #REQUIRED>
]>
<doc>
 <!--Start XSL-->
 <xsl:stylesheet id="stylesheet"
  version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform" >
  <xsl:template match="xsl:stylesheet" />
  <xsl:template match="/doc">
   <html>
    <head>
     <style type="text/css">
       <!-- Your CSS goes here -->
     </style>
     <script type="text/javascript">
       <!-- Your Javascript goes here -->
     </script>
    </head>
    <body>
     <table>
      <thead>
       <!-- Whatever is in here will get printed at the top of every page -->
      </thead>
      <tbody>
       <!-- Main HTML, including "canvas" tags etc. -->
      </tbody>
     </table>
    </body>
   </html>
  </xsl:template>
 </xsl:stylesheet>
 <!--Start XML-->
 <seriesdata>
  <datapoint x="2.1" y="3.0" />
  <datapoint x="2.9" y="5.2" />
 </seriesdata>
</doc>

Below is the bit of magic to draw up the XML data into Javascript memory space.  Assuming there is a Javascript constructor called ChartSeries that takes four parameters )name, array of x values, array of y values, color), the code below uses XSL to shove the x values inline in a comma-separated manner into the Javascript.

var mychartseries = new ChartSeries("Channel 1",[0
 <xsl:for-each select="seriesdata/datapoint">
  <xsl:value-of select="concat(',',@x)"/>
 </xsl:for-each>
 ],[0
 <xsl:for-each select="seriesdata/datapoint">
  <xsl:value-of select="concat(',',@y)"/>
 </xsl:for-each>
 ], "Yellow");
Posted by at No comments:
Labels:

Thursday, June 21, 2012

W7 can finally rotate bitmap fonts

With HTML5 canvas and its built-in ability to rotate text, I came across (i.e. learned the hard way) about the limitations of bitmap fonts, such as MS Sans Serif, in XP.  XP has trouble rotating bitmap fonts at small point sizes, while Windows 7 does not.  So the following HTML5 canvas code works in Windows 7 & Firefox but fails under XP & Firefox:
<html>
 <head>
  <script type="text/javascript">
   window.onload = function() {
    var ctx = document.getElementById('canvas').getContext('2d');
    ctx.translate(100,100);
    ctx.font = "9px MS Sans Serif";
    ctx.rotate(-Math.PI/2);
    ctx.fillText("TEST", 10, 10);
   }
  </script>
 </head>
 <body>
  <canvas id="canvas" width=800 height=500 />
 </body>
</html>
Switching to a TrueType font such as Arial solves the problem.  So the lesson is to avoid bitmap fonts such as MS Sans Serif when using HTML5 Canvas.

This change in font handling for Windows 7 is probably related to Microsoft's revamping of font scaling to deal with high-resolution netbooks with tiny screens.

Posted by at No comments:
Labels: ,

Sunday, June 17, 2012

HTML5 is the holy grail

I was initially excited about the UI design philosophy of Win8 Metro. But then I realized that HTML5 can do 95% of what Metro can, and also be truly cross-platform.

I see HTML5 as the cross-platform holy grail that developers have been seeking since the WORA days of Java 15 years ago. First it was supposed to be Java, then Microsoft embraced and extinguished it, and besides it had too big of a footprint download (and a clumsy download process to boot). Then Flash was supposed to be the universal small-footprint. It was just about to take off, then Apple extinguished it by not supporting it at all (completely skipping the "embracing" step). Then Microsoft finally decided to stop holding back .NET from web development -- the purpose for which it seemingly was originally designed but never delivered upon until Silverlight. But by then Windows market share was too small for Microsoft to force a Windows-only solution on the web world.

Even when it comes to CPU-intensive signal & image processing, Javascript seems to be "fast enough".  E.g. these guys show real-time 2-D FFT. Admittedly, the combination of SSE/AVX and multi-threading/multi-core would have provided a 30x speedup, but I've been playing around with real-time 2D graphics in JavaScript and have been amazed at its performance. I was even guilty of premature optimization -- I started out coding for double-buffering the graphics with two Canvases and ended up throwing out the double-buffering because with just one Canvas there was no flicker.

On today's processors, Javascript will be "fast enough" for many applications. E.g., I do scientific software for a living, and I'm partitioning the work into what has to be done natively -- mostly the acquisition and crunching of tens of gigabytes of data at a time -- vs. what can be done cross-platform -- the final post-processing of tens of megabytes of pre-processed data.

Javascript can even access hardware-accelerated 3D with WebGL.

HTML5 is W3C standard. It's not Sun. It's not Adobe. It's not Microsoft. It's W3C.

HTML5 is the holy grail of WORA.
Posted by at No comments:
Labels:
Subscribe to: Posts (Atom)