Shallow Thoughts : : Oct

Akkana's Musings on Open Source Computing and Technology, Science, and Nature.

Fri, 31 Oct 2008

GIMP Drag-n-Drop and Open Location without gvfs

Quite a while ago I noticed that drag-n-drop of images from Firefox had stopped working for me in GIMP's trunk builds (2.6 and 2.7); it failed with a "file not found" error. Opening URIs with Open Location also failed in the same way.

Since I don't run a gnome desktop, I assumed it probably had something to do with requiring gnome-vfs services that I don't have. But yesterday I finally got some time to chase it down with help from various folk on #gimp.

I had libgnomevfs (and its associated dev package) installed on my Ubuntu Hardy machine, but I didn't have gvfs. It was suggested that I install the gfvs-backends package. I tried that, but it didn't help; apparently gvfs requires not just libgvfs and gvfs-backends, but also running a new daemon, gvfsd. Finding an alternative was starting to sound appealing.

Turns out gimp now has three compile-time configure options related to opening URIs:

  --without-gvfs          build without GIO/GVfs support
  --without-gnomevfs      build without gnomevfs support
  --without-libcurl       build without curl support

These correspond to four URI-getting methods in the source, in plug-ins/file-uri:

GIMP can degrade from gvfs to gnomevfs to libcurl to wget, but only at compile time, not at runtime: only one of the four is built.

On my desktop machine, --without-gvfs was all I needed. Even without running the gnome desktop, the gnomevfs front-end seems to work fine. But it's good to know about the other options too, in case I need to make a non-gnomevfs version to run on the laptop or other lightweight machines.

Tags: , , ,
[ 12:09 Oct 31, 2008    More gimp | permalink to this entry | ]

Mon, 27 Oct 2008

An Arduino battery timer

I wrote in my OSCON report a few months back that I came home from the conference with an Arduino microcontroller kit and just enough knowledge and software to make LEDs blink. And so it sat, for a month or two, while I tried to come up with some reason I desperately needed a programmable LED blinker (and time to play with it).

But it turned out I actually did have a practical need for a customizable programmable gizmo. One of the problems with R/C combat flying is that you're so focused on keeping track of which plane is yours that it's tough to keep track of how long you've gone on the current battery. You don't want to fly a lithium-polymer battery until it gets so weak you notice the drop in power -- that's really bad for the battery. So you need a timer.

My transmitter (a JR 6102) has a built-in timer, but it's hard to use. As long as you remember to reset it when you turn on the transmitter, it displays minutes and seconds since reset. Great -- so all I need is somebody standing next to me who can read it to me. Looking away from the sky long enough to read the timer is likely to result in flying into a tree, or worse. (The new uber-fancy transmitters have programmable beeping timers. Much more sensible. Maybe some day.)

I could buy a kitchen timer that dings after a set interval, but what's the fun of that? Besides, I could use some extra smarts that kitchen timers don't have. Like audible codes for how long I've flown, so I can make my own decision when to land based on how much throttle I've been using.

Enter the Arduino. Those digital outputs that can make an LED blink work just dandy for powering a little piezo beeper, and it turns out the Atmel ATmega168 has a built-in clock, which you can read by calling millis().

So I wired up the beeper to pin 8 (keeping an LED on pin 13 for debugging) and typed up a trivial timer program, battimer.pde. It gives a couple of short beeps when you turn it on (that's so you know it's on if you can't see it), then gives a short beep at 9 minutes, a long one at 10, shorter one at 11, and thereafter gives (minutes MOD 10) beeps, i.e. two for 12, three for 13 and so forth. Fun and easy, and it works fine at the field once I worked out a way to carry it (it's in a camera bag hanging on my belt, with the beeper outside the bag so I can hear it).

Fun! It could use better codes, and a pause switch (for when I land, fiddle with something then go back up on the same battery). Of course, in the long run I don't actually want to devote my only Arduino kit to being a glorified stopwatch forever. I have further plans to address that, but that's for a later posting ...

Tags: , , ,
[ 13:10 Oct 27, 2008    More tech/hardware | permalink to this entry | ]

Sun, 26 Oct 2008

Two articles: Linux Bookmarklets

I've been writing a new series for Linux Planet, on Firefox Tricks. The first two articles cover bookmarklets, something I've mentioned a few times in this blog):

Simple Bookmarklets: The Power of the Command Line in your Browser
Roll Your Own Custom Bookmarklets In Firefox, part 2: Javascript Bookmarklets.

Tags: , , ,
[ 23:32 Oct 26, 2008    More writing | permalink to this entry | ]

Mon, 20 Oct 2008

Requesting no window decorations (and moonroot 0.4)

Someone on #openbox this morning wanted help in bringing up a window without decorations -- no titlebar or window borders.

Afterward, Mikael commented that the app should really be coded not to have borders in the first place.

Me: You can do that?

Turns out it's not a standard ICCCM request, but one that mwm introduced, MWM_HINTS_DECORATIONS. Mikael pointed me to the urxvt source as an example of an app that uses it.

My own need was more modest: my little moonroot Xlib program that draws the moon at approximately its current phase. Since the code is a lot simpler than urxvt, perhaps the new version, moonroot 0.4, will be useful as an example for someone (it's also an example of how to use the X Shape extension for making non-rectangular windows).

Tags: , , ,
[ 12:06 Oct 20, 2008    More programming | permalink to this entry | ]

Sun, 12 Oct 2008

More fun with regexps: Adding "[no output]" in shell logs

Someone on LinuxChix' techtalk list asked whether she could get tcsh to print "[no output]" after any command that doesn't produce output, so that when she makes logs to help her co-workers, they will seem clearer.

I don't know of a way to do that in any shell (the shell would have to capture the output of every command; emacs' shell-mode does that but I don't think any real shells do) but it seemed like it ought to be straightforward enough to do as a regular expression substitute in vi. You're looking for lines where a line beginning with a prompt is followed immediately by another line beginning with a prompt; the goal is to insert a new line consisting only of "[no output]" between the two lines.

It turned out to be pretty easy in vim. Here it is:

:%s/\(^% .*$\n\)\(% \)/\1[no results]\r\2/


starts a command
do the following command on every line of this file
start a global substitute command
start a "capture group" -- you'll see what it does soon
match only patterns starting at the beginning of a line
look for a % followed by a space (your prompt)
after the prompt, match any other characters until...
the end of the line, after which...
there should be a newline character
end the capture group after the newline character
start a second capture group
look for another prompt. In other words, this whole
expression will only match when a line starting with a prompt
is followed immediately by another line starting with a prompt.
end the second capture group
We're finally done with the mattern to match!
Now we'll start the replacement pattern.
Insert the full content of the first capture group
(this is also called a "backreference" if you want
to google for a more detailed explanation).
So insert the whole first command up to the newline
after it.
[no results]
After the newline, insert your desired string.
insert a carriage return here (I thought this should be
\n for a newline, but that made vim insert a null instead)
insert the second capture group (that's just the second prompt)
end of the substitute pattern

Of course, if you have a different prompt, substitute it for "% ". If you have a complicated prompt that includes time of day or something, you'll have to use a slightly more complicated match pattern to match it.

Tags: , , , ,
[ 14:34 Oct 12, 2008    More linux/editors | permalink to this entry | ]

Thu, 09 Oct 2008

Getting rid of .sudo_as_admin_successful

Ever been annoyed by the file in your home directory, .sudo_as_admin_successful? You know, the one file with the name so long that it alone is responsible for making ls print out your home directory in two columns rather than three or four? And if you remove it, it comes right back after the next time you run sudo?

Here's what's creating it (credit goes to Dave North for figuring out most of this).

It's there because you're in the group admin, and it's there to turn off a silly bash warning. It's specific to Ubuntu (at least, Fedora doesn't do it). Whenever you log in under bash, if bash sees that you're in the admin group in /etc/groups, it prints this warning:

To run a command as administrator (user "root"), use "sudo ".
See "man sudo_root" for details.

Once you sudo to root, if you're in the admin group, sudo creates an empty file named .sudo_as_admin_successful in your home directory. That tells bash, the next time you log in, not to print the stupid warning any more. Sudo creates the file even if your login shell isn't bash and so you would never have seen the stupid warning. Hey, you might some day go back to bash, right?

If you want to reclaim your ls columns and get rid of the file forever, it's easy: just edit /etc/group and remove yourself from the admin group. If you were doing anything that required being in the admin group, substitute another group with a different name.

Tags: , , , ,
[ 18:33 Oct 09, 2008    More linux | permalink to this entry | ]

Wed, 08 Oct 2008

Open Letter to Asus and Other Netbook Manufacturers

Dear Asus, and other manufacturers who make Eee imitations:

The Eee laptops are mondo cool. So lovely and light. Thank you, Asus, for showing that it can be done and that there's lots of interest in small, light, cheap laptops, thus inspiring a bazillion imitators. And thank you even more for offering Linux as a viable option!

Now would one of you please, please offer some models that have at least XGA resolution so I can actually buy one? Some of us who travel with a laptop do so in order to make presentations. On projectors that use 1024x768.

So far HP is the only manufacturer to offer WXGA, in the Mini-Note. But I read that Linux support is poor for the "Chrome 9" graphics chip, and reviewers seem very underwhelmed with the Via C7 processor's performance and battery life. Rumours of a new Mini-Note with a Via Nano or, preferably, Intel Atom and Intel graphics chip, keep me waiting. C'mon, won't somebody else step up and give HP some competition?

It's so weird to have my choice of about 8 different 1024x600 netbook models under $500, but if I want another 168 pixels vertically, the price from everyone except HP jumps to over $2000.

Folks: there is a marketing niche here that you're missing.

Tags: , , , ,
[ 22:50 Oct 08, 2008    More tech | permalink to this entry | ]

Sat, 04 Oct 2008

Console Setup in Ubuntu

Dave and I were testing some ways of speeding up the booting process, which is how he came to be looking at my Vaio's console with no X running. "What's wrong with that font?" he asked.

I explained how Ubuntu always starts the boot process with a perfectly fine font, then about 80% of the way through boot it deliberately changes it to a garbled, difficult to read that was clearly not designed for 1024x761. Been meaning for ages to figure out how to fix it, never spent the time ... Okay, it said "Setting up console font and keymap" just before it changes the font. That message should be easy to find. Maybe I should take a few minutes now and look into it.

The message comes from /etc/init.d/console-setup, which runs a program called setupcons, which has a man page. setupcons uses /etc/default/console-setup which includes the following section:

# Valid font faces are: VGA (sizes 8, 14 and 16), Terminus (sizes
# 12x6, 14, 16, 20x10, 24x12, 28x14 and 32x16), TerminusBold (sizes
# 14, 16, 20x10, 24x12, 28x14 and 32x16), TerminusBoldVGA (sizes 14
# and 16), Fixed (sizes 13, 14, 15, 16 and 18), Goha (sizes 12, 14 and
# 16), GohaClassic (sizes 12, 14 and 16).

The hard part of changing the console font in the past has always been finding out what console fonts are available. So having a list right there in the comment is a big help. Okay, let's try changing it to Terminus and running setupcons again. Nope, error message. How about VGA? Success, looks fine. That was easy!

But while I was in that file, what about the keymap? That's another thing I've been meaning to fix for ages ... under Debian, Redhat and earlier Ubuntu versions I had a .kmap.gz console map that turned my capslock key into a Control key (the way God intended). But Ubuntu changed things all around so the old fix didn't work any more.

I found a thread from December from someone who wanted to make the exact same change, for the same reason, but the only real advice in the thread involved an elaborate ritual involving defining keymaps for X and Gnome then applying them to the console. Surely there was a better way.

It seemed pretty clear that /etc/console-setup/boottime.kmap.gz was the keymap it was using. I tried substituting my old keymap, but since I'd written it to inherit from other keymaps that no longer existed, loadkeys can't use it. Eventually I just gunzipped boottime.kmap.gz, found the Caps Lock key (keycode 29), replaced all the Caps_Locks with Controls and gzipped it back up again. And it worked!

Gary Vollink has a more detailed description, and the process hasn't changed much since his page on Getting "Control" on the "Caps Lock".

Another gem linked to from the Ubuntu thread was this excellent article on keyboard layouts under X by Daniel Paul O'Donnell. It's not relevant to the problem of setting the console keymap, but it looks like a very useful reference on how various international character input methods work under X.

Tags: , ,
[ 22:33 Oct 04, 2008    More linux | permalink to this entry | ]

Thu, 02 Oct 2008

New Pho 0.9.6-pre3

I've released Pho 0.9.6-pre3. The only change is to fix a sporadic bug where pho would sometimes jump back to the first image after deleting the last one, rather than backing up to the next-to-last image. I was never able to reproduce the bug reliably, but I cleaned up the image list next/prev code quite a bit and haven't seen the bug since then. I'd appreciate having a few testers exercising this code as much as possible.

Otherwise pho is looking pretty solid for a 0.9.6 release.

Tags: , ,
[ 10:57 Oct 02, 2008    More programming | permalink to this entry | ]