Firefox about:config Tips and Tricks

Friday, January 12th, 2007

In this post I’ll outline some of my favorite custom configuration options for Firefox, which can be set from about:config. Some of these preferences do not exist by default, so you will have to right-click in about:config, select New, the type of preference, and then enter the preference name exactly as I have written it.


Type: Boolean
Possible Values: true, false
Setting this option to true will cause the url bar to auto complete urls. With this option, you can type the first few characters of a url, hit enter, and bingo, your at the site!
urlbar autofill screenshot

Note: It isn’t at first apparent how to stop the auto-completion at a certain point without going to the entire URL. For instance, if you want to go to a root domain, but the URL that starts to auto complete includes a specific page, just hit space after the domain name to stop the auto completion.

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The Achilles Heel of DTR

Saturday, October 15th, 2005

When building this site, I wanted to use a custom font for all the headings, and after reading the tutorial on Dynamic Text Replacement at A List Apart, I decided to try it. Following my common philosophy of never using someone else’s code when I can write my own, I created a custom DTR script. The main difference between mine and the one on A List Apart is that I wanted to output transparent PNGs. Unfortunately, it turns out that the GD library in PHP is incapable of generating transparent text when any characters in a font overlap. You can see this problem in action in this image, where the end of the u is covered up by the x.

Picture of text

After digging through the bug reporting system for PHP, I ran across one in which a guy wanted to output alpha anti-aliased lines to transparent PNGs, but was unable to because, for “historical reasons”, GD cannot blend images this way (the bug). One more classic example of not treating transparency as just another channel I suppose.

So in order to output text that will be alpha blended, you have to run imagealphablending($img, false) so that all drawing to a pixel overwrites the existing contents of it without trying to blend the drawn color with its current color. So since imagettftext() and imagefttext() draw each character separately, if they overlap at all, they will overwrite the previous character.

So until GD is changed to use a different blending model, outputting transparent text is impossible. I thought of reporting this as a bug, but it seems that this is how the php and gd developers want it to behave. Of course IE’s complete inability to render transparent PNGs means that there really isn’t much point anyway 🙁