OSD 700 project release 0.4

For school, I am doing project releases in courses OSD600 and OSD700.

In OSD600 I completed three iterations, 0.1-0.3. Now in OSD700, I need to do 0.4-1.0.

This post will outline what I did for 0.4.

I’ve started by taking Firefox bug 677122 which was labeled as “not quite as easy”. I am always up for a challenge. For the tl;dr check my diff.

I will talk about what I did right, what I did wrong, and what I learned.

Three main things I did in this release are:

Created a working Firefox build on Windows. Which was not quite as easy because of bug 718541. I ended up narrowing what was needed to get a working build, and adding my findings to the ticket. Now being able to reproduce this problem, in hopes that it can be used to track down the exact cause. The ticket is now fixed.

Got a working developer environment working on Windows with Visual Studio 2010. This took more time than I wanted, as I am so used to web development where things like firebug work right out of the box. In other courses and projects, the code base is small enough that I don’t need any real developer tools, except my mind.

The real work was done in bug 677122. I had three attempts on this, and will describe each one, and why the first two failed and last succeeded.

First attempt was to wire the go to anchor code to process media fragment code. This failed because process media fragment should not be called out of context. It was originally a protected function, so that there should of been a red flag that this was going to fail. I moved it to public, then in the anchor code I would get a reference to the media element, and call ProcessMediaFragment, which would crash when trying to grab the mLoadingSrc. I suspect this is due to the way the media element lives in the media document. I loaded up firebug and actually looked at it, and it did not even have a src attribute attached to it. Probably why it failed, as it was not completely what I wanted. I did manage to parse the fragment code so I knew the difference between a fragment and an anchor, which would be crucial in the third attempt.

Second attempt was to try to get around the loading src, by doing this at a different time, or by calling a different function. Both attempts failed for similar reasons. I don’t think the timing was even the problem, but the reference to the element itself. A media document’s video element is not complete, and should not be used as such. It is a different beast. I tried things like, LoadWithChannel and resetToURI which both failed because they would access an element that was not what they expected it to be. Again, it doesn’t have a src attribute like most media elements. I also tried to do the work in the InternalLoad function, before the anchor code. This failed for the same reasons, but did get me choking off the GoToAnchor code, which helped me find the next part.

Third attempt was actually putting together two elements from the failed attempts. I moved the check for anchor or fragment to the InternalLoad, where I choked off the anchor code. It was as simple as that. Check for fragment and choke of the anchor. Once done, let the rest of the code to continue on its way. I have created a patch for this and submitted it for feedback in the ticket.

The biggest lesson I learned was a soft lesson. I should of probably asked for help between Monday’s post and Wednesday’s post. In retrospect, reading those posts now, I can see the naivety in my attempts. I was so positive about some of my solutions, and I can see it in my words. This will get better when I get more comfortable in the community, as I have been here before.

Some smaller lessons were more technical things about Firefox code. Like how to get a reference, cast it, string management, etc. These are things specific to Firefox code, and not really C++.

Warning, some of the links to Firefox source code will bitrot as the code changes and the lines where things live changes. Not sure of a better way to link to the source code.

Thanks for reading 🙂


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