Posts Tagged ‘bug’

webOS list modelChanged bug

I ran into a bug with the webOS mojo framework a while ago, which I nailed down thanks to this forum post. Simply put, calling this.controller.modelChanged on a list doesn’t work properly if the user has scrolled down the list. With the dotspott webOS app I notice a gray rectangle popping up, obscuring the last 2 items in the list.

From pacemkr,

Calling this.controller.modelChanged on a list that has been scrolled past renderLimit will blank out the screen and not show the changes. This happens because modelChanged handler in the List widget resets renderOffset to 0. In other words the list widget assumes that the user is at the top of the list when modelChanged event happens. This is a pretty nasty bug.

The solution is to use mojo.setLengthAndInvalidate() instead:


While Mojo has been superseded by Enyo, this is still a pretty big deal, there’s still lots of Pixi and Pre models out there with webOS 1.4.5.

Unexpected results

Every once in a while I’ll test some piece of code and encounter a bug or some unexpected behavior that produces something weird, peculiar, or just something pretty damn cool. Here’s a perfect example,

weird output

This is from some vectorization code I’m working on. Just for the hell of it, I decided to run the output image (the one with the green pixels, which represents vertices of a polygon) through the vectorization algorithm again. The subsequent images show what happened as I kept running the vectorization algorithm on the output, in effect creating a feedback loop. (The colors that are present in the subsequent images are a result of an earlier stage in the vectorization process, the output of which is no longer adequately processed, resulting in the pattern that’s visible).