Have Phun?

22. March, 2008

Did you have Phun lately? No? Not sure? In that case, check it out! It’s great!

Phun is a “2D physics sandbox”. You can draw objects with your mouse and then have nature have its way with them. Even if that sounds stupid or a waste of time to you, check the flash video on the home page out. If you played with Lego or Fischertechnik as a child, this one is definitely for you (and since that was probably already a few years in the past: for your children, too).

On the site, you’ll find links to insane machines people have already built and of course, there is already a huge amount of videos on YouTube.

And last but not least, there is a Windows and Linux version (32 and 64bit!).

Have Phun!


The Top 50 Proprietary Programs that Drive You Crazy — and Their Open Source Alternatives

13. February, 2008

If you ever wondered whether you can do what do everyday on Windows with Open Source Software (OSS), here is a list of 50 common, proprietary applications and their OSS alternatives:

The Top 50 Proprietary Programs that Drive You Crazy — and Their Open Source Alternatives


Wrapping Reflection with FEST-Reflect

6. February, 2008

Tired of handling all those pesky exceptions in Java Reflection? I’ve patched commons-beanutils to convert them into RuntimeExceptions but the patch was rejected because it’s a breaking change. Now, you can try FEST Reflection.

FEST Reflection has a nice and small API with an emphasis on making it easy to produce readable code.

Links: Found on DZone Javalobby


Safer Java: Think Positive

2. February, 2008

If you’ve ever developed software for X11, you probably stumbled over “unmap”. For everyone else: If you wanted to make something in a X11 user interface visible, you’d set “unmap” to “false”. A great way to interrupt work because we’re not used to negative thinking. If I want to make something visible, I think “I set some attribute to true” not the other way round.

In Java, we have learned but some API still smells. Collection.isEmpty(), for example. With positive thinking, I think of collections with elements as “better” than one without, so I’d prefer Collection.hasElements() even though it’s longer and boolean properties should use “is” instead of “has”. Oh well. But it’s simple to fall for the negative trap in your daily work as well.

If you find yourself stumble mentally when using a boolean API, refactor and turn it positive. Modern IDEs make this simple and you’ll write more error-free code in less time. commons-lang offers isBlank() and isNotBlank for Strings which is a good example because you don’t have to put a “!” negator in your if’s no matter if blank is good or bad in your specific case and the JIT will inline the code anyway, so there isn’t even a speed penalty (only a LOC penalty).


Are You OSS? Why?

2. February, 2008

If you ever wondered why you’re using Linux while everyone in the office uses Windows at home, fret no more and read here.


Safer Java: No Pseudo Constants

24. January, 2008

Even the pros do it: String “constants” i.e. a string literal (that is something between ” quotes) used as a “constant”.

That’s almost as bad as using integer values as arguments instead of defining symbolic names for them! I mean, the values passed into this API are defined by the standard, aren’t they? Sure, you can pass additional feature names as well but that doesn’t stop anyone from defining those which the standard defines somewhere! So what that not all of them must be supported!

There are several reasons why you should always define string constants when your API need strings as parts of it’s “configuration”:

  1. It makes it much more simple to find possible values for your API.
  2. Auto completion in an IDE is possible and helps to avoid typos.
  3. You can add JavaDoc to your strings explaining what they do.
  4. Modern IDEs can find out where your strings are being used in the project.
  5. You can rename the constant and change the string value, even if you have several constants with the same value!
  6. Even if the literals are read from a file, still define a constant for the string and map the raw string to the constant as soon as possible. It makes it so much more simple to track!

Tip: If you still use Java 1.4, define your string constants in an interface (without any other methods). That allows you to use “implements” anywhere where you want to use the constant names without having to prefix them with the name of the interface:

public interface Constants {
    public final static String A = "a";
}

class Demo implements Constants {
    private String value = A;
}

With Java 5, you’ll use enum, of course (especially because you can then use these “strings” in switch statements.


Safer Java: Constants First

22. January, 2008

Here is a simple change in your Java development style that will save you a lot of time: When comparing something against a constant, always put the constant first. Examples:

    if (0 == x)...

    public final static String RUN = "run";
    if (RUN.equals (mode))...

That will look strange at first because we’re used to have the constants on the right hand side (from assigns). So what’s the advantage of this? There are three:

  1. It will save you a lot of NullPointerException when using equals().
  2. It’s more readable in big if/else “switch-alikes”, when you compare a variable against a lot of values.
  3. It avoids the accidental assignment as in if (x = 0) (which should have been if (x == 0) … and if you can’t see the difference between the two, you really should always do it this way!) because if (0 = x) generates a compile time error.

Portable UI

18. January, 2008

For many years, I’ve been looking for a way to write portable applications with a nice, responsive user interface. Many have tried and many have failed:

  • Python with tcl/tk – A nice experience from the developer side. The Python wrapper around the tk widget set shows how you can get compact, yet easy understandable code and write UI’s in short time. If it just weren’t that ugly …
  • Java with Swing – Swing borrows a lot from X11, the grandfather of all graphical desktops. I have yet to see anyone managing to impress the world with their grandfather …
  • Java with SWT – Now, here comes a contender. Java is pretty widely available (not quite as many platforms as Python, but still), it is pretty fast, okay, the download is a bit on the big side … but no DLL hell, easy to setup (especially if you don’t provide an installer and just push a ZIP out). SWT is nice, fast … and bare bones. MFC? Well, they have JFace and in a few years, there might even be a text editing component that can do word wrap and still show line numbers. Oh, and SWT is available on even fewer platforms than Java. Palm, anyone?
  • HTML – Web based apps are all the hype. If you want to use your app on the run, it gets tricky. I don’t know about the US, but here in Europe, going online with you mobile will ruin you. Literally. Also, I’ve had my struggles with HTML and CSS and I can do without. Either and both.

I’ve tried a few more but in the end, things never felt right. Until recently. I’m a big fan of treeline. Treeline uses Python and PyQt which wraps Qt (say: “cute”). Qt is a mature framework, currently at version 4.3.3, with 4.4 is around the corner. It doesn’t have all the nifty stuff I can imagine (like an RTF editor; QTextEdit can only do a (big) fraction of that) but it gets closer to what I want than anything else.

In the past two weeks, I wrote a little clone of yWriter4. The little baby has currently about 8000 loc and about half of the functionality I want to give it (especially the text editing is still leaving a lot to be desired). Except for two bugs (signal names and GC issues), it’s been a real pleasure to use. I managed to implement almost every feature within a few minutes or few hours (the storyboard took 6 hours, the scene chart view took two), also thanks to the good defaults of the framework. Here is an impression of v0.2:

So when you’re considering to write a small to medium sized application which needs to run on Windows, Linux and MacOS, give PyQt a try.


Sorting Number Table Columns in PyQt4

14. January, 2008

Here is a simple trick to sort number columns in the QTableWidget of Qt4 and PyQt4: Format the number as a right aligned string:

for i range(12):
    item = QTableWidgetItem(u'%7d' random.randint(1, 10000))
    item.setTextAlignment(Qt.AlignRight)
    table.setItem (i, 1, item)

Testing JavaScript

14. January, 2008

If you’re test mad like me, then the <script> tag in HTML was probably one sore spot for you as it was for me: How to test the damn thing? Well, now, there is a way: John Resig wrote a small script which you can source into Rhino 1.6R6 (or later; 1.6R5 won’t work, though. You’ll get “missing : after property id”). Afterwards, you’ll have window, document, nagivation, even XMLHttpRequest!

Yes, you can actually test AJAX within unit tests, now! TDD fans, start your engines!

Unfortunately, it doesn’t emulate browser bugs, yet ;-> But you can fix that. I, for example, had problems to get the code load HTML 3.2 files. Especially this code made the SAX parser vomit:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 //EN">

The fix here is to download some XHTML DTD (like XHTML 1 Strict), put it somewhere (along with the three entity files xhtml-lat1.ent,
xhtml-special.ent and xhtml-symbol.ent) and change the DTD to point to the new file:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 //EN" "html/xhtml1-strict.dtd">

In my case, I’ve put the files in a subdirectory “html/” of the directory I start the tests from. (Hm … shouldn’t this path be raltive to the HTML file?? Well, it isn’t.)

Also, the env.js supplied doesn’t support forms. Here is my which fix:

function collectForms() {
    document.forms = document.body.getElementsByTagName('FORM');
    
    for (var i=0; i<document.forms.length; i++) {
        var f = document.forms[i];
        f.name = f.attributes['name'];
        //print('Form '+f.name);
        f.elements = f.getElementsByTagName('INPUT');
        
        for(var j=0; j<f.elements.length; j++) {
            var e = f.elements[j];
            var attr = e.attributes;
            
            forEach(attr, print);
            e.type = attr['type'];
            e.name = attr['name'];
            e.className = attr['class'];
            
            _elements[ f.name + '.' + e.name ] = e;
        }
        //print(f.elements);
    }
}

Note: I also had to remove the calls to toLowerCase() for the tag names (*not* the attributes!), too. Otherwise, document.body would return UNDEFINED for me. But that’s because I’m stuck with old HTML; If you can convert all tag and attribute names to lowercase, then you’re safe.

Lastly, the loading of the document is asynchronous. To fix this, we need a class to synchronize the Java and the JavaScript thread. That one is simple:

package test.js;

import org.mozilla.javascript.ScriptableObject;

import test.ShouldNotHappenException;

public class JSJSynchronize extends ScriptableObject
{
    public Object data;
    public Object lock = new Object ();
    
    @Override
    public String getClassName () {
        return "JSJSynchronize";
    }
    
    public Object jsGet_data() {
        synchronized (lock) {
            try {
                lock.wait ();
            }
            catch (InterruptedException e) {
                throw new ShouldNotHappenException(e);
            }
            
            return data;
        }
    }

    public void jsSet_data(Object data) {
        synchronized (lock) {
            this.data = data;
            lock.notify ();
        }
    }
    
    public Object getData() {
        synchronized (lock) {
            try {
                lock.wait ();
            }
            catch (InterruptedException e) {
                throw new ShouldNotHappenException(e);
            }
            
            return data;
        }
    }

    public void setData(Object data) {
        synchronized (lock) {
            this.data = data;
            lock.notify ();
        }
    }
    
}

ShouldNotHappenException is derived from RuntimeException. After registering that with

        jsjSynchronize = (JSJSynchronize)cx.newObject (scope, "JSJSynchronize");
        scope.put("jsjSynchronize", scope, jsjSynchronize);

in the test, I can use the new jsjSynchronize global variable in JavaScript in wondow.onload:

    public void testAddTextFilters() throws Exception
    {
        setupContext ();
        addScript(cx, scope, new File ("html/env.js"));
        cx.evaluateString(scope, 
                "window.location = 'file:///d:/devm2/globus/abs/webapp/html/testAbsSkuOutput.html';n" +
      "window.onload = function(){n" +
      "    jsjSynchronize.data = window;n" +
      "};n" +
      "", "", 1, null);
        
        ScriptableObject window = (ScriptableObject)jsjSynchronize.getData();
        System.out.println ("window="+window);

At this point, the document has been loaded and you can access all the fields, elements, etc. Good luck!