Shallow Thoughts : : Jul

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

Wed, 29 Jul 2009

Emacs: Insert tags in HTML Mode

Wouldn't it be nice if Emacs HTML mode had a way to insert HTML tags, so you didn't have to type <b></b> all the time? Sort of like what's described in this page -- except that page describes an HTML mode that clearly isn't the one that's installed on Ubuntu, since none of those bindings actually work?

I've been meaning to figure out a way to do that for ages, and finally got around to it. Turns out Emacs SGML mode (which is really what Ubuntu installs and uses for HTML files) doesn't have functions for specific HTML tags like <b>, but it does have a general tag-inserting function.

Type C-c C-t -- emacs prompts you for the tag, so type b or whatever, and hit return -- and you get the tag, with the cursor correctly positioned for you to type your new bold text.

But that's four keystrokes. What if you want shorter bindings for particular tags, like C-b C-b to insert a bold?

For that, you need to use a lambda and a mode hook. In your .emacs it looks like this:

;; Define keys for inserting tags in HTML mode:
(defun html-hook ()
  (local-set-key "\C-c\C-b" (lambda () (interactive) (sgml-tag "b")))
(setq sgml-mode-hook 'html-hook)

There's apparently also supposed to be a command bound to C-c / that closes the current tag, but my version of sgml-mode doesn't bind anything to that key, and the only likely-looking function name, sgml-maybe-end-tag, doesn't end the current tag. Such is life!

But one more don't-miss feature that I'd missed all along is C-c C-n: type it before a special character like < or & and emacs will insert the appropriate &lt; or &amp; for you. Nice!

(Thanks to bojohan on #emacs for the tips!)

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[ 21:31 Jul 29, 2009    More linux/editors | permalink to this entry | ]

Tue, 21 Jul 2009

Tracking down performance hogs

It's been a day -- or week, month -- of performance monitoring.

I'm posting this while sitting in an excellent OSCON tutorial on Linux System and Network Performance Monitoring, by Darren Hoch. It's full of great information and I'm sure his web site is equally useful.

And it's a great extension to topic that's been occupying me over the past few months: performance tracking to slim down software that might be slowing a Linux system down. That's the topic of one of my two OSCON talks this Wednesday: "Featherweight Linux: How to turn a netbook or older laptop into a Ferrari." Although I don't go into anywhere near the detail Darren does, a lot of the principles are the same, and I know I'll find a use for a lot of his techniques. The talk also includes a free bonus tourist tip for San Jose visitors.

Today's Linux Planet article is related to my Featherweight talk: What's Bogging Down Your Linux PC? Tracking Down Resource Hogs. Usually they publish my articles on Thursdays, but I asked for an early release since it's related to tomorrow's talk.

For anyone at OSCON in San Jose, I hope you can come to Featherweight late Wednesday afternoon, or to my other talk, Wednesday just after lunch, "Bug Fixing for Everyone (even non-programmers!)" where I'll go over the steps programmers use while fixing bugs, and show that anyone can fix simple bugs even without any prior knowledge of programming.

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[ 11:58 Jul 21, 2009    More conferences | permalink to this entry | ]

Tue, 14 Jul 2009

Quick Firefox tip: Hide the "Additional plugins" bar

Dave just discovered a useful preference in Firefox.

Firefox 'additional plugins are needed to view this page' bar

So many pages give that annoying info bar at the top that says "Additional plugins are needed to view this page." It doesn't tell you which plugins, but for Linux users it's a safe bet that whatever they are, you can't get them. Why have the stupid nagbar taking up real estate on the page for something you can't do anything about?

Displaying the info bar is the right thing for Firefox to do, of course. Some users may love to go traipsing off installing random plugins to make sure they see every annoying bit of animation and sound on a page. But Dave's excellent discovery was that the rest of us can turn off that bar.

The preference is plugins.hide_infobar_for_missing_plugin and you can see it by going to about:config and typing missing. Then double-click the line, and you'll never see that nagbar again.

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[ 12:09 Jul 14, 2009    More tech/web | permalink to this entry | ]

Sun, 12 Jul 2009

Newbie Greasemonkey script writing

I was reading a terrific article on the New York Times about Watching Whales Watching Us. At least, I was trying to read it -- but the NYT website forces font faces and sizes that, on my system, end up giving me a tiny font that's too small to read. Of course I can increase font size with Ctrl-+ -- but it gets old having to do that every time I load a NYT page.

The first step was to get Greasemonkey working on Firefox 3.5. "Update scripts" doesn't find a new script, and if you go to Greasemonkey's home page, the last entry is from many months ago and announces Firefox 3.1 support. But curiously, if you go to the Greasemonkey page on the regular Mozilla add-ons site, it does support 3.5.

I've had Greasemonkey for quite some time, but every time I try to get started writing a script I have trouble getting started. There are dozens of Greasemonkey tutorials on the web, but most of them are oriented toward installing scripts and don't address "What do you type into the fields of the Greasemonkey New User Script dialog?"

Fortunately, I did find one that explained it: The beginner's guide to Greasemonkey scripting. I gave my script a name (NYT font) and a namespace (my own domain), added http://** for Includes, and nothing for Excludes.

Click OK, and Greasemonkey offers a "choose editor" dialog. I chose emacs, which mostly worked though the emacs window unaccountably came up with a split window that I had to dismiss with C-x 1.

Now what to type in the editor? Firebug came to the rescue here.

I went back to the NYT page with the too-small fonts and clicked on Firebug. The body style showed that they're setting

font-family: Georgia, serif
font-size: 84.5%

84.5%? Where does that come from? What happens if I change that to 100%? Fortunately, I can test that right there in the Firebug window. 100% made the fonts fairly huge, but 90% was about right.

I went back to greasemonkey's editor window and added: = "90%";

Saved the file, and that was all I needed! Once I hit Reload on the NYT page I got a much more readable font size.

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[ 12:30 Jul 12, 2009    More tech/web | permalink to this entry | ]

Thu, 09 Jul 2009

Twittering -- and writing Twitter clients

I finally dragged myself into 2009 and tried Twitter.

I'd been skeptical, but it's actually fairly interesting and not that much of a time sink. While it's true that some people tweet about every detail of their lives -- "I'm waiting for a bus" / "Oh, hooray, the bus is finally here" / "I got a good seat in the second row of the bus" / "The bus just passed Second St. and two kids got on" / "Here's a blurry photo from my phone of the Broadway Av. sign as we pass it" -- it's easy enough to identify those people and un-follow them.

And there are tons of people tweeting about interesting stuff. It's like a news ticker, but customizable -- news on the latest protests in Iran, the latest progress on freeing the Mars Spirit Rover, the latest interesting publication on dinosaur fossils, and what's going on at that interesting conference halfway around the world.

The trick is to figure out how you want the information delivered. I didn't want to have to leave a tab open in Firefox all the time. There was an xchat plug-in that sounded perfect -- I have an xchat window up most of the time I'm online -- but it turned out it works by picking one of the servers you're connected to, making a private channel and posting things there. That seemed abusive to the server -- what if everyone on Freenode did that?

So I wanted a separate client. Something lightweight and simple. Unfortunately, all the Twitter clients available for Linux either require that I install a lot of infrastructure first (either Adobe Air or Mono), or they just plain didn't work (a Twitter client where you can't click on links? Come on!)

But then I tried out the Python-Twitter bindings, and they were so easy to use I decided to write them up for my next Linux Planet article, which came out today: Write Your Own Linux Twitter Client In Less Time Than It Takes To Find One!.

The article shows how to use the bindings to write a bare-bones client. But of course, I've been hacking on the client all along, so the one I'm actually using has a lot more features like *ahem* letting you click on links. And letting you block threads, though I haven't actually tested that since I haven't seen any threads I wanted to block since my first day.

You can download the current version of Twit, and anyone who's interested can follow me on Twitter. I don't promise to be interesting -- that's up to you to decide -- but I do promise not to tweet about every block of my bus ride.

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[ 16:09 Jul 09, 2009    More writing | permalink to this entry | ]

Thu, 02 Jul 2009

Disabling mouse/keyboard wakeup

Suspend (sleep) works very well on the dual-Atom desktop. The only problem with it is that the mouse or keyboard wake it up. I don't mind the keyboard, but the mouse is quite sensitive, so a breeze through the window or a big truck driving by on the street can jiggle the mouse and wake the machine when I'm away.

I've been through all the BIOS screens looking for a setting to flip, but there's nothing there. Some web searching told me that under Windows, there's a setting you can change that will affect this, but I couldn't find anything similar for Linux, until finally drc clued me in to /proc/acpi/wakeup.

cat /proc/acpi/wakeup
will tell you all the events that can cause your machine to wake up from various sleep states.

Unfortunately, they're also obscurely coded. Here are mine:

Device  S-state   Status   Sysfs node
SLPB      S4    *enabled  
P32       S4     disabled  pci:0000:00:1e.0
UAR1      S4     enabled   pnp:00:0a
PEX0      S4     disabled  pci:0000:00:1c.0
PEX1      S4     disabled  
PEX2      S4     disabled  pci:0000:00:1c.2
PEX3      S4     disabled  pci:0000:00:1c.3
PEX4      S4     disabled  
PEX5      S4     disabled  
UHC1      S3     disabled  pci:0000:00:1d.0
UHC2      S3     disabled  pci:0000:00:1d.1
UHC3      S3     disabled  pci:0000:00:1d.2
UHC4      S3     disabled  pci:0000:00:1d.3
EHCI      S3     disabled  pci:0000:00:1d.7
AC9M      S4     disabled  
AZAL      S4     disabled  pci:0000:00:1b.0

What do all those symbols mean? I have no clue. Apparently the codes come from the BIOS's DSDT code, and since it varies from board to board, nobody has published tables of likely translations.

The only two wakeups that were enabled for me were SLPB and UAR1. SLPB apparently stands for SLeeP Button, and Rik suggested UAR probably stood for Universal Asynchronous Receiver (the more familiar term UART both receives and Transmits.) Some of the other devices in the list can possibly be identified by comparing their pci: codes against lspci, but not those two.

Time for some experimentation. You can toggle any of these by writing to the wakeup device:

echo UAR1 >/proc/acpi/wakeup

It turned out that to disable mouse and keyboard wakeup, I had to disable both SLPB and UAR1. With both disabled, the machine wakes up when I press the power button. (What the SLeeP Button is, if it's not the power button, I don't know.)

My mouse and keyboard are PS/2. For a USB mouse and keyboard, look for something like USB0, UHC0, USB1.

The UAR1 setting is remembered even across boots: there's no need to do anything to make sure the setting is remembered. But the SLPB setting resets every time I boot. So I edited /etc/rc.local and added this line:

echo SLPB >/proc/acpi/wakeup

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[ 10:21 Jul 02, 2009    More linux/kernel | permalink to this entry | ]