Blog

Not your regular TI-83

2008-11-04T18:05:00.001Z

I've only ever owned one graphical calculator, a TI-83, which was bought for me around when I started Secondary School. It was the device on which I broke my programming teeth, making crummy games and utilities to make maths exercises less tedious.

The other week I was experimenting with the HTML Canvas element for another little side-project of mine when I was reminded of the Graph Plot screen which my old calculator has. Essentially it lets you enter a Cartesian equation which it will then plot on the screen.

Subsequently, over a couple of days I put together a Javascript powered equation plotter, with much the same functionality as my TI-83. Oh and in the process I found a bug in the WebKit nightly, which they swiftly fixed.

You're free to use the source to the how you wish, if you're that way inclined (it's a client-side web script so it's practically open source off the bat). Under the hood it makes use of the MooTools javascript framework, though I've not made use of its features extensively, so It would only be a matter of an evening's work to remove this dependancy.

A case of bad cropping

2008-08-23T22:41:00.000+01:00

Recently, by pure chance, I've been working for two different research projects which both have involved Java Applets.

The first project ran afoul of bug #6669818 which prevented the applet from connecting back to the originating server during LiveConnect calls, in Mozilla Firefox on a Windows XP platform.

Fortunately there is a workaround for this; by passing the task off to another thread which was started in a non-LiveConnect part of the Applet's lifecycle, the task is then executed in another thread which is not subject to the same malfunctioning security check.

If you'd rather not have to create a thread just for this, a quick hack is to pass the event off to the applet rendering thread using the SwingUtilities.invokeLater(Runnable); function.

In the second project I've now encountered another platform-specific Applet quirk, this time with Mac OSX.

Using Javascript it is possible to change the size of an Applet on the page in the same way you would any other DOM element, however on Mac OSX any browser using the Java Embedding Plugin (Firefox, Opera and others) will fail to resize Java Applets correctly.

I've knocked up a simple test page which allows this to be tested, and shows a potential workaround.

There appear to be two problems cropping up; the first is that the Browser does not notify the Applet that it ought to resize. If you leave the "Notify Java" check-box un-checked when submitting the form, the browser expands the area the Applet ought to be using, but the applet continues to draw in it's original position.

The second issue is that when axis are changed and Java is manually notified the behaviour still does not perform as it ought to. The clipping region of the Java applet rendering is not updated correctly, and thus only part of the applet is correctly rendered.

There is a temperamental workaround for this, by programatically resizing one axis and then the other in quick succession, but this seems to fail as often as it works, depending on whether the page is being loaded from nothing, refreshed, no-cache refreshed or returned to via the browser 'Back' action.

In the interest of getting this bug fixed the code to the Applet resize test page is linked from the test page and free for all to use.

Bugs:

Java Embedding Plugin tracker: #2030298
Firefox Bugzilla: #451882

Urestrict BBC Radio iPlayer

2008-04-01T13:35:00.000+01:00

As long as I can remember, the BBC's online music streaming service has restricted the control you have on playback streams, restricting the embedded realplayer controls to allow you pause, skip 5 minutes or skip 15 and change the volume. I can understand the legal obligations they may have, but from a piracy perspective stopping people skipping tracks is irrelevant, its only use is as a measure to stop people re-listening to the same track without having to go back to the start each time.

The controls on Mac OS X are less restrictive, but still restrict you to pause, fast forward or stop, however some simple javascript manipulation of the page can enable the regular RealPlayer controls, complete with a seek-bar.

Bookmark either download the source file or view the bookmarklet source. Unfortunately blogger won't let me create an actual bookmarklet link, so you will manually have to save the bookmarklet into a bookmark in your browser.

Google Maps Placemark

2008-03-01T10:00:00.003Z

This post has been sitting for quite a while now, pending me having time to sit down and write some text to go alongside the code. It would appear that I now have the time to write it up.

Back when I was writing my Google Maps property finder I was using Google's Geocoding API to get a set of co-ordinates based on a search string.

Specifically I was using the getLocations method of the GClientGeocoder object. This would return a number of Placemark objects with a bunch of information about the potential matches. They don't really document this object, but to be honest they don't really need to, below is an example Placemark expressed in JSON-ish notation.

{   "id": "p1",
    "address": "1600 Amphitheatre Pkwy, Mountain View, CA 94043, USA",
    "AddressDetails": {
        "Country": {
            "CountryNameCode": "US",
            "AdministrativeArea": {
                "AdministrativeAreaName": "CA",
                "SubAdministrativeArea": {
                    "SubAdministrativeAreaName": "Santa Clara",
                    "Locality": {
                        "LocalityName": "Mountain View",
                        "Thoroughfare": {
                            "ThoroughfareName": "1600 Amphitheatre Pkwy"},
                            "PostalCode": {
                                "PostalCodeNumber": "94043"
                            }
                        }
                    }
                }
            },
        "Accuracy": 8
        },
    "Point": {
        "coordinates": [-122.081783,37.423111,0]
    }
}

The only thing is, if you want to get a specific element, the tree will not necessarily be the same each time, so traversal is a pain. The code below will condense all this into the root level of an object, so you can pick out the key/value pairs you want, and easily tell if some aren't there.

var Placemark = new Class({
 initialize: function(placemark){
  this.traverse(placemark);
 },
 traverse: function(item, key) {
  for (var key in item) {
   
   if (key == 'prototype')
    continue;
    
   if(typeof(item[key]) != 'object')
    this[key] = item[key];
   else
    this.traverse(item[key]);
  }
 }
})

One thing to note is that this was written for to use the Mootools class system, though it shouldn't be very hard to remove this dependancy.

Leaked UK National ID Register Document

2008-01-29T11:25:00.001Z

In response to a post on boingboing requesting mirrors for a leaked document, here is my mirror copy. Enjoy :)

Spring MVC Wizards & Form Taglib

2008-01-26T16:30:00.000Z

I've been building a JSP based website for a course module titled "Technologies for Electronic Commerce". It's finished now, but I've only just got round to writing up this post.

As part of this I was trying to make a multi-page form, using Spring's AbstractWizardFormController and spent an hour or so trying to make the form submission change the form page. My problem was that it wasn't immediately obvious how to use the form taglib with the Wizard architecture.

The docs mentioned using request parameters, which was a bit confusing as I was using a POST form submission, however all you actually need to do is add one of these parameters to the form data (usually using a button).

Finish and cancel actions can be triggered by request parameters, named PARAM_FINISH ("_finish") and PARAM_CANCEL ("_cancel"), ignoring parameter values to allow for HTML buttons. The target page for page changes can be specified by PARAM_TARGET, appending the page number to the parameter name (e.g. "_target1"). The action parameters are recognized when triggered by image buttons too (via "_finish.x", "_abort.x", or "_target1.x").

For example:

<input value="Submit" name="_target1" type="submit"/>

This will request to change to page 2 of the form (remember Array base is 0). Because of the way forms work, you can have a number of these (either as clickable images or buttons) and only the one the user eventually selects will be submitted with the request.

Making the most of Pandora.com

2008-01-05T22:08:00.001Z

Pandora.com is pretty cool, it's been around for a while now but I just went back to it for some easy listening background music to work to. Supposedly they've begun to use IP filtering to limit the audience to the US. Either this is no longer in place or they've made a mistake in a regex somewhere, as this is definitely not the US. I'd forgotten about the limit to the unpaid service, which stops playback after so many songs, but it was quite a while before I actually encountered it. This may be a Mac OS X bug in the flash implementation, but it seems that if you keep the Firefox window containing the player minimised in the Dock, the music doesn't stop playing! Of course this does get in the way of the whole feedback system slightly, but I'm sure there are those who won't mind too much. Once I did encounter the limit I couldn't just refresh the page and go back to listening again as they're smart enough to stop you doing that. But not that smart. To completely stop this you would require either some heinous DRM-spawn system describable as cookies which you can't delete, or some kind of unique client ID, effectively voiding all browser privacy. So to be fair, from the technologies they had to work with, they've done the best they could. ;) So once you've been shut out of the Pandora player try the following:

Delete your cookies from their domains.
Delete any data stored within Adobe Flash for their domain.

The latter can be achieved by opening the Adobe Flash client settings and changing the data limit for the domain to 0KB, which will take effect upon refreshing the page, upon which the flash applet will request to store data in your browser again, and you're back listening, but without any of your stations.

Update:

It appears that the region filtering will go live on January 15th, not quite yet.

Hello World!

2007-12-19T23:00:00.000Z

I've been here before, set up a new blog and then proceeded to ignore it. There's still a chance of that happening, but this time I'm not deluding myself that this is the new awesome thing (TM), perhaps I'll get into the habit but likely I won't. The difference this time is that I've given up on using Wordpress for my own blog. I should clarify (after such a flame-bait-ish statement) this isn't due to anything I dislike about Wordpress, rather my own observations about my needs (read: user requirements). Part of this comes from my ill-advised creation of a university society web-page through a large mangling of Wordpress categories and templates. It really was not needed. Sure the website needed a refresh, but only visually, we weren't that busy a society to warrant a plethora of categories. So, back to basics and reign in the enthusiasm. :)

Maintenance

I said before, I have a tendency not to come back to blogging very often, so while I'm usually in favor of updates for the sake of updates, installing a new version every time I come back to blog briefly is not something I can be bothered to do, but paradoxically rather than ignore it, I opt to not blog instead.

Spam

Spam is a pain and I'd much rather let someone else deal with it than moderate my own comments or find the right plugin to install.

Features

Features are lovely, everyone loves features, but frankly they're wasted on me, I probably don't use most of Wordpress's features anyway. So, the answer is clearly some managed solution, the few candidates that come to mind:

Wordpress.com: Wordpress is Ok but to be honest I fancy a change, and there's no point having my domain if I don't use it.
Livejournal: Livejournal is for some reason too old fashioned for my tastes, plus it's got a whole layer of social networking and crap which I waste enough time with on Facebook.
Blogger: It's Google for a start, so they get the benefit of the doubt in the new features department, plus they have a handy thing which lets them publish via SCP to my domain.

Hardly a convincing argument I know, but that's about as far as I bothered to look. Anyways, goodbye for now blogosphere, let's keep in touch.