Yenya's World

Sat, 09 Jun 2007

PNG Transparency III.

A while ago I wrote about PNG transparency in MSIE. Today we have discovered another strange bug^H^H^Hbehaviour of MSIE with respect to the AlphaImageLoader:

We use generated PNG images as a substitute for mathematical formulas. A common character in those formulas is the plus (+) sign. However, it seems that AlphaImageLoader sends this character unescaped (a plus sign in the URL is to be interpreted as space), so the plus sign disappears from the resulting image.

I have tried to replace plus sign with %2B (an ASCII code of this character), but it did not help. Apparently, AlphaImageLoader receives the URL in its argument with plus sign correctly escaped, but it unescapes it and sends the HTTP request with a bare plus sign.

The solution was then obvious: replace the %2B strings in the image URL with %252B (0x25 is the ASCII code of the percent sign). Now back to the (mostly) sane world of UNIX.

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Fri, 08 Jun 2007

New Strings

Last week I broke the strings on my squash racket while playing with Míra Pečený. This week I played with new strings on my racket for the first time. It was excellent - the new strings were harder, and allowed more precise hits ...

... until I cracked the racket. Oh well.

a broken squash racket

Does anybody know about a good e-shop with squash rackets? The one I used last time ( has been sold to some other owner since last time I bought something from them.

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Thu, 07 Jun 2007

Fedora 7

Just a brief note on my experience with Fedora 7: I have installed in on my laptop the day before the release, and now I have all my workstation except my dual-seat home computer upgraded. I have not found any significant changes in the user interface (which I guess is good). Newer versions of everything, of course (read the Release notes for an official list).

In the day of the release, we have even tried to use the second gigabit uplink of the faculty network, so the output of our FTP server has briefly exceeded 1 Gbit/s several times. So what are you waiting for? It is time for upgrade, and F7 will definitely not bite you!

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Wed, 06 Jun 2007

Oracle Unbreakable Support

A comedy of the day is yesterday's Dave Jones' blog post. Have fun!

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Tue, 05 Jun 2007

MOXA the Braindead

I hereby declare that MOXA engineers are complete idiots. Pardon my strong wording, and read on why do I think so.

There are many systems for transporting RS-232C serial connection over something else than a standard, but way too big DB-9 (or even DB-25) connector. Since the structured cabling is very common these days, many RS-232C systems use the 8-pin RJ-45 connector for it. However, there is no standard defining the pin assignment for the RJ-45 with RS-232C. For example, Cisco uses its own wiring for their serial consoles, Cyclades has its own, etc. And there is one more problem: RS-232C defines nine signals, while the RJ-45 connector has only eight pins.

Cyclades serial boards, which we have used for a while, employed a quite smart approach to this problem: their expansion boxes were equipped with RJ-50 sockets (RJ-50 is a 10-pin backward compatible variant of RJ-45: the RJ-45 jack can be plugged into the RJ-50 socket, leaving the pins 1 and 10 of RJ-50 unused). Cyclades put all important signals of RS-232C to pins 2 to 9, and they have put a signal "RI" (Ring Indicator), which is rarely used these days, to the pin #1. So almost everybody could use standard RJ-45 connectors and UTP cables, and those who really needed the RI signal could do it using the RJ-50 connector. Unfortunately, Cyclades has been bought by Avocent, and they no longer produce multiport serial boards.

Now MOXA C32081T expansion box uses RJ-50 as well, with 9 pins out of 10 assigned. But guess how "smart" is their pin assignment: they use pin #1 (which is not available when using the RJ-45 connector) for a "DCD" (carrier detect) signal, which is often needed, and they use two other pins (#4 and #7, I think) for a signal ground (GND). And then they state in the documentation, that either of these pins can be used, and it is not necessary to connect both. Moreover, The "RI" signal is not available in their connector. So they have forced their customers to use a completely obscure connector while not using the two more pins to anything meaningful, and still not having a complete set of RS-232C signals.

My dear lazyweb, does anybody know where to buy a pack of RJ-50 connectors and a crimping tool for it?

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Fri, 01 Jun 2007

RPM on a Multiarch System

Another command of the day, this time related to the RPM package manager on a multi-architecture system (the one which contains libraries for multiple architectures; typicaly an AMD64 system allows to run both i386 and x86_64 binaries):

$ echo '%_query_all_fmt        ' \
  '%%{name}-%%{version}-%%{release}.%%{arch}' \
  >> ~/.rpmmacros

This way the rpm -qa command displays also the architecture of the packages in its output.

Section: /computers (RSS feed) | Permanent link | 2 writebacks


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