2009-07-27
Displaying images with Self
The Self source code has some example programs, one of which is a web browser. This was developed quite a long time ago and is unable to nicely display most pages on the modern web but it does a reasonable job of basic pages. On the Linux port there were some problems with displaying images however. I tracked this down to two issues:
- It only natively decoded image formats that aren't really used on the web (Sun Raster format for example). The GIF and JPG handling code spawned external programs, which I didn't have on my Linux install, to convert to a format it could handle before displaying.
- There was a bug in the color management code on X11 for displays greater than 8 bit.
The first was a quick fix by changing the programs that it used to do the conversion to one readily available on Linux. I changed it to use the Image Magick 'convert' program. This enabled displaying code in an imageMorph by setting the image for the morph:
setImage: ui2Image copyFromGIFFile: 'test.gif'
I tracked the second issue down to code that was sending a message to an object that didn't understand that message (Static typing fans can say 'I told you so' here). Self has a 'paintManager' which handles color mapping for displays that can't display a large number of colors. On 8 bit displays this is a 'paintManager'. On displays with more colors it's a 'unmappedPaintManager'. The latter doesn't have some of the slots of the former and there was code trying to do this. I changed this to check if the paintManager instance can do color mapping before sending the messages.
With that change the web browser could display images. An example page that works with the browser (one of the few...), and code to display it:
'http://www.bluishcoder.co.nz/self/imagetest.html' asURL getPageForUser
The patches with these fixes are available from the webbrowser branch of my fork of the Self git repostory on github. The fixes were only a few lines of code.
I did a short screencast showing loading image morph's and displaying the web page in the browser. And before you say, "wow, that GUI looks so 90's", don't forget - it was.
