I Do Exist, Honest!

After a stressful day I appear to exist once again. If you tried to visit my blog yesterday you would have seen that it had been removed. Worse than that Google had decided to suspended my entire account. That meant I lost access not only to all my blogs, but photos in picasa, my calendars, my gmail account, and my Google+ profile. It was almost as if I no longer existed (online). I filled in the contact us form to request my account back and then almost a day later I got this e-mail from Google:

We apologize for any inconvenience you may have experienced. The issue you described should now be resolved.

I don't think I've ever been quite so relieved. While the whole experience was a bit of a nightmare it did get me thinking about how I could keep backups of all my Google data in case something similar happened again in the future. After a little bit of hunting around the web (via Google of course) I came across the Data Liberation Front.

The Data Liberation Front is a Google engineering team who are trying to make it easy to liberate your data from Google products. This is useful for either moving your data to a competing service or for simply backing it up locally.

They have step by step instructions on exporting your data from most of Google's products, but they are also developing Google Takeout. Google Takeout brings together a number of the export tools into a simple interface allowing you to select which data you want to download. It then collects the data together into a single zip file that you can easily download and archive. Currently it supports: +1’d sites, Buzz, Contacts and Circles, Picasa Web Albums, Profile, and Google+ Stream. As far as I can tell the aim is to add more products to this list and I'd certainly appreciate Blogger being included.

So if you don't have a recent backup of your Google hosted data maybe now is the time to do something about it.

Striped Clouds

I've spent quite a bit of my spare time over the last week or two doing some Java GUI programming, the reasons for which will become clear in a later post. Quite a lot of the GUI is table based and so I've spent quite a bit of time playing with custom rendering code for different data types to make things easier to visualize and edit. There are plenty of tutorials on how to do this spread over the web but one thing I found quite difficult was writing a renderer that worked reliably across different Java Look and Feels (L&F). The one renderer I wrote that highlights most of the problems I had was for displaying a checkbox in a table.

By default Java will display a checkbox for boolean data types, but unfortunately it doesn't disable the checkbox when it can't be edited. This leads to a situation where you can't change the state of the checkbox but there is no visual feedback to tell you this. So I wrote a simple renderer that would disable the checkbox if it wasn't editable. The first problem I found was that under the GTK+ L&F the background of the cell didn't change when the row was selected. It did under the default Metal L&F and after a little bit of debugging I discovered the problem. Every Swing component has an opaque property which determines if it's background is drawn or not. It turns out that the default value is dependent on the L&F. So under Metal checkbox's have an opaque background while under GTK+ they don't. Fortunately this is easy to fix simply by calling setOpaque(true). A similar problem occurs with the focus rectangle around the outside of each table cell, but again it's an easily fixed by calling setBorderPainted(true). These tweaks gave me a cell renderer which seemed to work well until, that is, I tried it under the Nimbus L&F.

The Nimbus L&F was introduced in Java SE 6 Update 10, and was meant to be the new cross platform L&F that would replace the aging Metal which has been the default since Swing was first developed. One of the nice things about Nimbus is that it is resolution independent and uses vector graphics rather than bitmaps. This should, in theory, lead to a crisper interface. Personally I'm not a fan, and as yet it hasn't replaced Metal as the default L&F. It seemed, however, sensible to make sure my rendering code worked correctly under Nimbus as well as Metal, GTK+ and CDE/Motif (these are the four L&Fs available by default when running Java under Ubuntu). Unfortunately it didn't.

Nimbus, in an attempt to be different, colours the background of table rows alternating colours -- by default white and a light gray. This is instead of drawing a border around the cells. The problem is that my renderer (and almost every example I've seen) gets the background colour for the cell from the table by calling either table.getBackground() or table.getSelectionBackground(). The selected background colour works correctly but the unselected cells get drawn with a dark gray background. There are three tricks to work around this while leaving the code working under the other L&Fs. The first is to get the alternative background colour from the UIManager class. The second is to recreate the unselected background colour to make it display correctly. Finally we use the modulus operator to determine which row colour we should be using. Adding these workarounds gives me the following cell renderer which seems to work under the four L&Fs available by default under Ubuntu as well as the Windows L&F.

import java.awt.Color;
import java.awt.Component;

import javax.swing.BorderFactory;
import javax.swing.JCheckBox;
import javax.swing.JTable;
import javax.swing.UIManager;
import javax.swing.border.Border;
import javax.swing.table.TableCellRenderer;

/**
 * A TableCellRenderer for JCheckBox that disables the checkbox when the
 * cell isn't editable to make it clear that you can't click on it
 * 
 * @author Mark A. Greenwood
 */
@SuppressWarnings("serial")
public class CheckBoxTableCellRenderer extends JCheckBox implements
                                                    TableCellRenderer {

  private static final Border NO_FOCUS =
    BorderFactory.createEmptyBorder(1, 1, 1, 1);;

  public CheckBoxTableCellRenderer() {
    super();
    setHorizontalAlignment(JCheckBox.CENTER);
    setBorderPainted(true);
    setOpaque(true);
  }

  public Component getTableCellRendererComponent(JTable table,
    Object value, boolean isSelected, boolean hasFocus,
    int row, int column) {

    // this is needed for Nimbus which has alternative rows in different
    // colors hopefully other L&Fs that also do this use the same key
    Color alternate = UIManager.getColor("Table.alternateRowColor");

    // strangely the background color from nimbus doesn't render properly
    // unless we convert it in this way. I'm guessing the problem is to do
    // with the DerivedColor class that Nimbus uses
    Color normal = new Color(table.getBackground().getRGB());

    if(isSelected) {
      setForeground(table.getSelectionForeground());
      setBackground(table.getSelectionBackground());
    } else {
      setForeground(table.getForeground());
      setBackground(alternate != null && row % 2 == 0 ? alternate : normal);
    }

    setEnabled(table.isCellEditable(row, column));
    setSelected(value != null && (Boolean)value);

    if(hasFocus) {
      setBorder(UIManager.getBorder("Table.focusCellHighlightBorder"));
    } else {
      setBorder(NO_FOCUS);
    }

    return this;
  }
}

One thing to note is that I've used the alternative colour for the even numbered rows (i.e. when row % 2 == 0). I've seen some web pages suggesting that you need to use the alternative colour on the odd rows. I'm not sure how Nimbus decides which colour to use for which rows so if you see them switched around for some reason you'll need to tweak the code slightly (i.e. use row % 2 == 1).

Quick As A Fox

I like watching films and I buy a lot of DVDs (there are almost 500 movies in the house). I tend to find though, that often I have a completely different view to most movie critics so I don't tend to read movie reviews or magazines. I do, however, find watching movie trailers useful (the one exception being The Break Up, which I thought looked great but definitely wasn't) so I can easily waste an hour or so on the iTunes Movie Trailers website. Yesterday, having read an article about possible Oscar contenders I went to hunt down the trailer for The Descendants only to find that the trailer wouldn't play.

My main PC runs Ubuntu and in the past Apple have gone out of their way to make it difficult to watch the trailers on Linux so I just assumed they had deliberately broken something. I had a quick hunt around the web and couldn't see anyone else complaining that things had changed recently so I decided it had to be a problem on my machine. It took me a while to track down the problem but I thought it worth mentioning here just in case it trips up anyone else. Essentially VLC was the cause of the problem.

I use VLC as the main video player on my computer as it works well with DVDs and almost any file format/codec combination you throw at it. However, I'd recently had a problem with the audio and video going out of sync. While trying to fix that problem I had done a complete reinstall of VLC. As well as reinstalling the main application this had also reinstalled too Firefox plugins. It turns out that one of these plugins seems to interfere with the Totem based QuickTime plugin. I'm guessing that the VLC plugin takes presedence and then fails for some reason. The easy solution is to simply disable one of the VLC based Firefox plugins. You can do this from the addons page in Firefox (accessed by entering about:addons in the address bar). You should find two plugins named 'VLC Multimedia Plug-in'. The difference between them is that one states it is compatible with Totem. Leave this one alone and disable the other one and hey presto! QuickTime movies should start playing again.

Given that before the reinstall of VLC trailers had been playing properly, I'm guessing that I'd worked this problem out before and then forgotten all about it (memory like swiss cheese and all that), so hopefully this post should at least remind me of the solution next time I have the same problem even if it doesn't help anyone else.

Off The Tracks

Error handling is always important. Nobody likes it when an application they are using crashes so badly that it stops working. Of course some application crashes are more embarrassing or public than others. On my way back from a work meeting in Prague last week I saw a perfect example in Huddersfield train station.

Fortunately a simple ArrayIndexOutOfBoundsException didn't seem to stop the trains running on time.

Browser Detection: How Not To Do It

Web browsers used to behave so differently from one another that it was common to write code to detect which browser type and version was being used to display the page so that appropriate code could be run. Fortunately, modern browsers tend to support web standards better and so apart from a few CSS tweaks it is unusual to come across browser detection code (the one exception to this rule being the expense system I have to use at work which doesn't seem to like Firefox at all). So I was a little surprised the other day when I suddenly found myself bounced to a an unsupported browser page on a shopping site that I'd been browsing around a few days before. So being the inquisitive kind I had a dig around and came across this gem.

if (navigator.userAgent.match(/Firefox\/[12]/)) {
   window.location.href = "unsupported.html";
}

For those of you who don't speak JavaScript, this essentially checks (using a regular expression) for the presence of either "Firefox/1" or "Firefox/2" in the useragent string, which identifies the make and version of the web browser requesting the page.

Now I like living on the bleeding edge of browser development and so I run the nightly builds of Firefox. Given the recent change in the release cycle of Firefox, the version number has climbed quite rapidly and the nightly build now sends the following useragent string (you can find out where your browser sends using this website):

Mozilla/5.0 (X11; Linux x86_64; rv:10.0a1) Gecko/20111012 Firefox/10.0a1

So from reading this you should be able to see that I'm actually running version 10.0a1 of Firefox. It should also be clear why the check of my browser resulted in me being bounced to the unsupported browser page: Firefox/10.0a1 contains the string "Firefox/1". This is a good example of why you really shouldn't write your own browser detection code, especially as there are a number of well written and up to date scripts out there that correctly extract the make and version number and which are easy to use. And if you subscribe to the not-invented-here school of thought, then at least make sure you actually implement a sensible solution!

Postvorta: Providing Intelligent Blog Search

The eagle-eyed amongst you may have noticed that about a month ago the search box in the sidebar of this blog changed. I used to use the standard Google search gadget but I now use a gadget powered by Postvorta.

Postvorta was built specifically to enable intelligent searching of blogs. How do I know this you ask? Well I spent the past year building Postvorta in my spare time. The initial motivation was a number of conversations with fellow bloggers about the inadequacies of the Google search gadget and coupled with the fact that my job involves processing natural language documents (I work as part of the GATE group at the University of Sheffield) I thought I was in a position to provide something better.

It is difficult to know exactly how the standard Google search gadget works, but as far as I can tell (both from personal experimentation and from talking to others) it appears to only index the main content of each post. For example, it certainly doesn't index the labels associated with posts. This means that while you can view all posts with a given label you can't search for them using the search gadget. Postvorta, however, indexes all the important content from your blog posts: title, article, labels, and comments. Importantly it does not index the pages you see when you view the blog in a web browser, instead it access the underlying data (via the Google Data APIs) which means that it can ignore the repeated information in the blog template. For example, many blogs contain a gadget which lists recent post titles, these shouldn't be indexed with each post as that makes it much more difficult to search for the actual post. A search can also be restricted by date and/or by the people who commented on a post. I've tried to provide as much flexibility as possible while keeping the full interface relatively simple.

Fortunately when building Postvora I didn't have to start from scratch. One advantage of working in a research group that makes their software available under an open-source license is that I can make use of software I use at work in my own projects. In this case the main indexing and search facilities behind Postvorta are built upon GATE Mímir. I've talked about Mímir before on this blog and if you've read that post then you shouldn't be surprised that as well as searching for words, like Google and the other search engines, you can use Postvorta to search your blogs semantically, i.e. for things. So you can search for any posts containing, for example, the name of a person without knowing what the name was in advance. If you are new to Mímir then Postvorta provides a comprehensive description of the query syntax which becomes available when you choose to use it through the search interface (by default searches are treated as a simple bag-of-words just as with other search engines).

Feel free to have a play with Postvorta through the search gadget on this blog. I'm also using it on my main blog where there are a lot more posts to search through. Postvorta is currently being run as a closed beta (while I evaluate performance, reliability etc.) but if you like what you see then you can register your interest and I'll try and index your blog as soon as possible -- note that currently Postvorta only supports Blogger blogs, although WordPress support should be coming soon.

Let me know what you think.

Blogger's Lightbox Returns To Haunt Our Blogs!

Blogger have now reintroduced lightbox to all blogs. While they claim to have fixed a lot of the bugs/issues that were reported before, they have still turned lightbox on by default. Fortunately we don't need to apply a hacky workaround this time.

If you don't want to use lightbox then you can turn it off for each blog you write through your dashboard. Simply select “No” next to Lightbox in the Settings > Posts and Comments section (new interface) or the Settings > Formatting section (old interface). I still think this feature should be opt-in rather than opt-out but at least they are allowing us to opt-out, so I guess we should be grateful.