Think Diff

Posted by Orville Bennett on July 13, 2008
Read time: about 2 minutes

Apple has an interesting little utility which they provide with Xcode called FileMerge. I don’t actually know if it merges files as the name implies, but I would assume so. I’ve been using it to see file diffs here on os x. It seems to be a quick and dirty app, but it’s easy to use and works well (albeit without the visual pulchritude of your typical os x programs).

So now you might be wondering (or if you’re me reading this a few months from now, I might be wondering) why I was using this. Well. Amarok 2 (yes, that again) has recently, due to a number of breakthroughs gained the ability to play audio, and lo, video on os x; as long as the path to the file being played doesn’t contain a space. After e-mailing the phonon-backend dudes, i got an informative e-mail from Richard @ Nokia/Trolltech (née Trolltech) informing me that the latest qt snapshot might have a fix for this. Thank you Richard! qt-copy is still @ 4.4.0 though which means those trying the KDE/Mac packages would miss this fix until qt-copy got synched to 4.4.2 (and who knows when that’ll happen). Solution: patch!

qt-copy has a directory for patches so I added one after hunting down the code necessary to fix the problem in one of the qt 4.4.2 snapshots. It’s the snapshot from 2008-07-08 for those of you wondering. Now KDE/Mac packages should pick up the fix when the patch is applied. Just need to update the A2 on OS X wiki to inform those building from source that they’ll need to run apply_patches in src and then we’ll be “GOOD 2 GO!” as Elephant Man usually says.

But back to FileMerge; so I used it to compare all the .cpp files in the src/3rdparty/kdebase/runtime/phonon/qt7/ directory of qt-copy and the qt-snapshot. Near the “end of the line” I got a one-liner in quicktimevideoplayer.cpp. Not even a one-liner, a one-worder. While it seemed that this might be the change Rich @ Trolltech was referring to, I was a bit skeptical. I decided to go do the same in phonon for qt’s kdelibs dir; looking for more substantial changes. There were a LOT more files there. Owing the that, and the speed of my new macbook (make -j4 is awesomeness people) I decided to just compile the change and test to see if that actually fixed the problem. And lo! It did.

Index: src/3rdparty/kdebase/runtime/phonon/qt7/quicktimevideoplayer.cpp
--- src/3rdparty/kdebase/runtime/phonon/qt7/quicktimevideoplayer.cpp    (revision 820342)
+++ src/3rdparty/kdebase/runtime/phonon/qt7/quicktimevideoplayer.cpp    (working copy)
@@ -451,7 +451,7 @@</code>
 void QuickTimeVideoPlayer::openMovieFromUrl()
-    QCFString urlString = QCFString(m_mediaSource.url().toString());
+    QCFString urlString = QCFString(m_mediaSource.url().toEncoded());
     CFURLRef url = CFURLCreateWithString(0, urlString, 0);
     DataReferenceRecord dataRef = {0, 0};
     QTNewDataReferenceFromCFURL(url, 0, &amp;dataRef.dataRef, &amp;dataRef.dataRefType);

Whodathunk? I’d started looking into fixing this bug right before I wrote the phonon-backend ML and I’m glad they already fixed this. If I had continued I’d still be pouring over the audio* or backend* files trying to figure out where it all went wrong. Maybe even media. Would’ve never suspected the quicktimevideo.cpp file though. After all, I was getting the bug for audio too, the problem couldn’t be in there … *sigh See what (almost) happens when we assume?

I’m pretty happy with that. I’m still “new” to the whole “software design/programming” (as opposed to hacking) thing so I’m relatively confident I wouldn’t have found and fixed the bug in a timely manner, if at all. Unless I really tried; which, I rarely do. I know, I suck, but my eyes start glossing over at around hour 3 with nothing still done :-/