One cute hack for MacOS X (... or nice internet protocol helper hacks...)

[Andre Garzia]

Hi Folks,

this email is about a little nice hack I made today. Here I present  
the steps for making URLs like:

x-dreamcard://www.mysweetserver/mySweetStack.rev

Open inside Revolution app, even when inserted inside HTML files  
rendered by Safari or the like. So this is about Registering a new  
protocol and protocol helper application in MacOS X. When you type a  
URL in MacOS X, for example:

http://www.runrev.com

The system first try to recognize the HTTP protocol, if it does, then  
it looks for an app that can handle this kind of protocol, in my case  
Safari, then it passes an AppleEvent GURLGURL with the URL for the  
application. So we can create a new protocol called x-dreamcard and  
associate it with Revolution, this way, when the user access a URL  
that uses x-dreamcard as the protocol, Revolution will receive the  
GURLGURL AppleEvent with the URL. I named the protocol x-dreamcard  
here for some reasons, first it's advised by many groups of very  
important IETF members that all protocols that are not approved by  
IETF (this experimental) be prefixed with an X and a dash. I also was  
trying to open the URL in the Dreamcard Player but since the player  
and Rev shares the same creator codes, my system finds that Rev is  
the default application for REVO creator code.

We can associate creator codes with protocols using something called  
LaunchServices (new MacOS X thingy), or you can use some tool like  
MoreInternet (http://www.monkeyfood.com/software/moreinternet/). So  
the steps are:

	(1) Download moreInternet.
	(2) Use it to add x-dreamcard protocol and associate it with Rev.

This takes care of the Operating System part, now onto Rev.  
Revolution does not deal with GURL AppleEvents by default so what we  
do is write a little plugin that is loaded as backscript on startup,  
this script traps all AppleEvents looking for a GURL, if it receives  
it, the it loads the file, the script I use is below:

on appleEvent pClass,pID,pSender
     if pClass is "GURL" and pID is "GURL" then
         request appleEvent data -- get the content of the AppleEvent
         replace "x-dreamcard" with "http" in it
         go stack URL it
     end if
     pass appleEvent
end appleevent

We need to replace the x-dreamcard protocol in the AppleEvent data  
because this protocol don't actually exists, it's just a little tag  
to tell the system: "Hey load this stuff on Revolution!"

What can you do with things such as this? Well, you can create  
educational resources as HTML and create little demo stacks, when the  
user clicks on the demo stack links inside the HTML, the app will  
load on demand inside Revolution (or Dreamcard player, whichever is  
available, you could even create your own loader using splash  
techniques), which would be a very easy student user experience.

I created this to see if I could, it involves lots of customizations,  
quick ones, but some effort, maybe someone might do clever things  
with it, I just wanted to share.

Cheers
andre