AIGLX/Beryl

Beryl is a super-sweet, super-configurable fork of Compiz (also see earlier post). Here I will describe how I got it set up on my system and some cool things to do with it. Setup Here are my specs:

• 2 Hyundai 17" screens
• 32-bit OS (Ubuntu Edgy Eft 6.10)
• nVidia Geforce graphics card

Following the instructions on the Unofficial Edgy Eft Starter Guide, I got AIGLX/Beryl to work on only one screen without problems. To enable Twinview (sharing one desktop accross two physical screens), enter sudo nvidia-settings in a terminal and go to X Server Display Configuration (this, by the way, beats the hell out of hacking the /etc/X11/xorg.conf file). Click the Configure... button on the middle right and select Twinview. Be sure to back up your xorg.conf file before clicking Save to X Configuration File at the bottom and then exiting out of the settings manager. Hit Ctrl+Alt+Backspace to restart the X server. Unfortunately, Beryl on Twinview made windows appear without titlebars or borders. I also got this message in the terminal when I disabled the session startup scripts and tried to run beryl-manager in the terminal: beryl: No GLXFBConfig for depth 32 beryl: No GLXFBConfig for depth 32 beryl: No GLXFBConfig for depth 32 So, to the xorg.conf file! Under the Screen section, add this line: Option "AddARGBGLXVisuals" "true" I restarted the X server again and everything worked fine. Well, let me qualify that: at least nothing was obviously wrong. Some things are still somewhat slow like window resizing and scrolling. It appears that others are having similar problems. However, this works well enough for me. Features/Cool things to do All these commands (and the themes) are completely configurable... just fool with the settings by clicking on the red stone in the system tray and selecting one of the managers... here are just some of the default settings

• Ctrl+Super_L: water drop on desktop (hold down keys and move mouse for trail)
• Shirt+F7: Window wake
• Shirt+F9: Raindrops
• Super+Mouse Wheel: Zoom
• Alt+Mouse Wheel: Make a window transparent/opaque
• Super+N: Make a window negative
• Super+M: Make the whole screen negative
• Alt+Left Mouse Button: Drag a window
• Alt+Click Wheel: Resize a window
• Ctrl+Alt+Left/Right: Spin the cube
• Ctrl+Alt+Left Mouse Button: Drag the cube
• Alt+Tab: Switch applications
• F10: Expose-like effect

Here's where to configure desirable features in the Beryl Settings Manager:

• A 3D world: Have windows separated in a third dimension from each other (drag and rotate the cube to see!)
• Animations: Flames, Magic Lanterns and such
• Scale: Expose-like effect

Some Beryl demos on YouTube

How to get a RSS feed from a Twitter account

So it seems that Twitter has killed RSS feeds (I'm not sure what that has to do with implementing OAuth), but fortunately, there's an easy workaround.

You can get an RSS feed by querying another URL for the desired user. For instance, to get the RSS feed for user ggreenwald, you can find the feed at this url: http://twitter.com/statuses/user_timeline/ggreenwald.rss

Facebook Wall question

I sometimes have the question asked of me, "Danny, you are such a strong advocate of transparency and access; aren't you being a hypocrite by not allowing others to comment on your Facebook wall?"

This has always struck me as a rather strange question because it confuses the obligations of a person with the obligations of a state or corporation. It is true that I think that, say, governments should be relatively transparent -- that's a prerequisite for accountability. I, on the other hand, am a priori accountable to no one so I don't have those same obligations.

This accusation is analogous to claiming that WikiLeaks is a hypocritical organization because its members don't share all their internal communication with the world (many in the mainstream media do make this point after each release from WikiLeaks in order to discredit the organization). As if 1) there is any equivalence between the transparency obligations of states/corporations and activist groups or 2) WikiLeaks isn't facing an existential threat from organizations that would use that internal information to try and destroy the group.

But that aside, there is a valid question contained within the query. Why do I have the personal preference of configuring my Facebook Wall settings in such a way? I just don't feel that it is worth the time and mental strain to police my Facebook profile 24/7 to expunge things said by others (whether said out of malice, ignorance or superfluousness) that I would rather not have on there. There are sufficient potentially undesirable comments that may be put on one's profile for this to be a valid concern.

Multidimensional arrays with GCC's variable length arrays

GCC's extensions allow you to do some crazy things with multidimensional arrays. For C99, GCC implements variable-length arrays. So a declaration like this:

int matrix[a][b + 1];

Can be passed by reference to a function with this prototype:

void foo(int a, int b, int matrix[a][b+1]);

Or, if you want to get really crazy, you can use forward declarations and change around the parameter order:

void foo(int a; int b; int matrix[a][b+1], int a, int b);

No malloc needed! Much better than the old way.

Which application is using that port?

See which ports are open, as an attacker would:

nmap 127.0.0.1

(Superuser seems to need to be used on some the following commands)

See which process is using port 25:

netstat -nlp | grep 25

Same, with a bit less info:

fuser -n tcp 25

Or you could also do:

fuser -u smtp/tcp

Discovered here

Sansa Clip and Karmic

Upon upgrade to Karmic Koala Ubuntu (9.10), my trusty Sansa Clip player was not autodetecting like it did under the Ubuntu distribution I was previously using. So I scoured the web and found this site which gives a workaround: when the Sansa Clip is disconnected, go to Settings->USB Mode on the Sansa Clip and set it to MSC. It should now present itself to the computer as a normal file system. Unless, of course, the file system is screwed up, in which case you'll have to go to Settings->Format and format the Sansa Clip drive before connecting it again.

Funny C tricks

Taken from Bill Rowan's Stanford ACM presentation:

The "downto" operator:

int main()
{
int i = 5;
while(i --> 0) // --> is the downto operator!
{
  printf("%d\n", i);
}
return 0;
}

Cast any type to "bool" type (that is, 1 or 0):

!!foo

"Computed goto" (compiler-dependent && unary operator):

void print_loop(int s, int e) {
 assert(s < e);   
 top:    
 printf("%d\n", s);  
 goto *( &&top + ( !!(s++/e) ) * ( &&end - &&top ) );    
 end:  
 ;
}