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Monthly Archives: November 2007

While hunting down broken images in the pdf import, I came across a very weird behaviour, that was seemingly caused by plain C stream IO: every once in a while, streams that were explicitely opnened in binary mode converted 0x0A into 0x0D. One-on-one substitution, not the usual 0x0A to 0x0A 0x0D lineend conversion, notably. I wasted about a day trying to track that down, suspecting everything from crazy filesystem flags, to symbol hijacking during link time (i.e. somebody sneaking in own fwrite/putc/whatever into the binary). Laboriously ruled out one after the other.

Finally, I did what I should have done in the first place: I used a different hex editor. And lo and behold, the trusty midnight commander showed all the files with correct 0x0A. Caught in the act and proven guilty: emacs’ hexl-mode.

Well, kind of. It turned out to be a rather unlucky combination of things going wrong: emacs with its buffer encoding scheme, which tries to be smart and detect the actual encoding – if there’s a 0x0A in the file before a 0x0D, emacs assumes raw-text-unix and leaves line ends alone. If there’s a 0x0D in the file before any 0x0A, emancs assumes raw-text-mac, and converts all assumed lineends to 0x0D. And since hexl-mode seems to work on top of an existing buffer (and never loads the file directly from disk), this resulted in the described mess.

So, to save yourself some trouble: don’t trust your tools. And make sure to have files you want to work on with hexl-mode match something in file-coding-system-alist’s content, that enforces binary reads (elc, png, jpeg, ar, gz etc. for my setup).

Being honoured to mentor Shane Matthews on his GSoC 2007 project Impress OpenGL rendered transitions, I today received the mentor gift – thank you Google for the tshirt!

On related news, the resulting CWS got recently merged to HEAD, so those of the adventurous kind can now build this as an optional feature: just issue “build ENABLE_OPENGL=TRUE” in the slideshow module to be blessed with an ogltrans shared lib. And thanks to Rene, after CWS configure22 is integrated, one can even give “–enable-opengl” on the configure line. After that, register the ogltrans lib into OOo via unopkg, and use this presentation file to see what others are missing.

This could even be shipped as a separate extension after 2.4 is out…


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