With the release of J 7.01 Jsoftware “deprecated” COM. J 6.02 can run as a COM automation server but J 7.01 cannot.¹ Throwing COM under the bus is hardly radical. Microsoft, COM’s creator, has been holding COM’s head underwater for years. Many .Net programmers cringe when they hear the word “COM” and the greater nonwindows² world never really accepted it. COM is a complex, over-engineered, proprietary dead-end. Yet despite its bloated deficiencies a lot of useful software is COM based. So with COM going away, at least for J programmers, the hunt is on for viable replacements and while we’re hunting let’s rethink our entire approach to building J GUI applications.

J GUI applications are traditional desktop applications. They’re built on native GUIs like Windows Forms and GTK and when done well they look and act like GUI applications coded in other languages. This is all good but there is a fundamental problem with desktop GUIs. There are many desktop GUIs and they do not travel well. Programmers have spent many dollars and days creating so-called cross-platform GUIs but, if you wander off the Windows, Mac and Linux reservation, the results are not particularly portable. And, as portable GUIs rarely outperform native alternatives, programmers tend to stick in their tribal silos. GUI programming is a bitch, has always been a bitch and will always be a bitch. It’s time to divorce the desktop GUI bitch.

All divorces, even the geeky GUI variety, are hard. When you finally cut the knot you’re not entirely sure what you’re doing or where you’ll end up. All you know is that there is a better way and with respect to J GUI applications I believe that JHS is that way. JHS leverages the large CSS, HTML and JavaScript (CHJ) world and in recent years some impressive browser-based applications have emerged from that world. The application that changed my mind about JavaScript and browser-based applications in general is something called MathJax.

MathJax typesets mathematics. It renders both LaTeX and MathML using fully scalable browser fonts. This is better than what WordPress does. The following Ramanujan identity taken from MathJax examples renders on WordPress as an image.

MathJax renders the same expression with scalable fonts and supports downloading the expression as LaTeX or MathML text. This is pretty impressive for browser JavaScript. I wondered how hard it would be to use MathJax with JHS and was pleased to find it’s easy peasy.

Writing a basic JHS application is a straightforward task of setting up three JHS J nouns HBS, CSS and JS.³ HBS is a sequence of J sentences where each sentence yields valid HTML when executed. JHS generates a simple web page from HBS and returns it to the browser. MathJaxDemo HBS is:

 HBS=: 0 : 0
 navul''           
 '<hr>','treset' jhb 'Reset'

 '<hr>',jhh1 'Typeset with MathJax and J'
 configjax
 oltypeset''
        
 '<hr>',jhh1 'Typeset Random Expression Tables'
 tabledesc
 '<br/>','ttable' jhb'Typeset Random Expression Array' 
 '<br/>','restable' jhspan''        
 )

CSS is exactly what you expect: CSS style definitions. Finally, JS is application specific JavaScript. MathJaxDemo JS matches HBS page events with corresponding JHS server handlers. This demo uses ajax for all event handlers.

JS=: 0 : 0

 function ev_ttable_click(){jdoajax([],"");}
 function ev_tquad_click(){jdoajax([],"");}
 function ev_tmaxwell_click(){jdoajax([],"");}
 function ev_tramaujan_click(){jdoajax([],"");}
 function ev_tcrossprod_click(){jdoajax([],"");}
 function ev_treset_click(){jdoajax([],"");}

 function ev_ttable_click_ajax(ts){jbyid("restable").innerHTML=ts[0]; MathJax.Hub.Typeset();}
 function ev_tquad_click_ajax(ts){jbyid("resquad").innerHTML=ts[0]; MathJax.Hub.Typeset();}
 function ev_tmaxwell_click_ajax(ts){jbyid("resmaxwell").innerHTML=ts[0]; MathJax.Hub.Typeset();}
 function ev_tramaujan_click_ajax(ts){jbyid("resramaujan").innerHTML=ts[0]; MathJax.Hub.Typeset();}
 function ev_tcrossprod_click_ajax(ts){jbyid("rescrossprod").innerHTML=ts[0]; MathJax.Hub.Typeset();}

 function ev_treset_click_ajax(ts){
   jbyid("restable").innerHTML=ts[0]; jbyid("resquad").innerHTML=ts[0];
   jbyid("resmaxwell").innerHTML=ts[0]; jbyid("resramaujan").innerHTML=ts[0];
   jbyid("rescrossprod").innerHTML=ts[0];
 }

Running the JHS MathJaxDemo is a simple matter of:

1. Downloading the J scripts in the MathJaxDemo folder to a local directory.
2. Editing J’s ~config/folders.cfg file and pointing to your download directory with the name MathJaxDemo. You are set up correctly if jpath '~MathJaxDemo' returns your path.
3. Loading the demo: load '~MathJaxDemo/MathJaxDemo.ijs'
4. Browsing to the site: http://127.0.0.1:65001/MathJaxDemo

It’s not hard to use JHS as a general application web server. JHS provides many common controls right out of the box but to compete with desktop applications it’s necessary to supplement JHS with JavaScript libraries like MathJax. In coming posts I will explore how to use industrial strength JavaScript grids and graphics with JHS.

Screen shot of JHS MathJaxDemo running on Ubuntu.