Emacs screencast: rectangles

I've just made a screencast about using rectangles in Emacs, so I figured I should explain how I made it.

I made it with ScreencastMode for Emacs - which I happen to be the author of.
With it, you can create a screencast by writing the manuscript for the screencast in a mix of natural language and elisp. The playing of the screencast itself is handled by Emacs - by stepping through the manuscript at pace equivalent to as if a human had done them. The video-recording at youtube is done using this.
The mode supplies utility functions for the producer such as pauses, slow typing, and blinking regions.

A simple example screencast file looks like:

(require 'screencast) (screencast '( "This is the message-buffer." (i "This is the command-buffer.")n "I will now show you how to save the command-buffer:" (save-buffer) ) "sample" 1.1 )

Which results in the following buffer output when the screencast has been played to the end.
Notice how the message-buffer contains the description of the commands done on the command-buffer. That is the way it works: the message-buffer describes what is going on in the command-buffer

More screencast sources can be found here.

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Some critical questions has been asked about ScreencastMode, here are my attempts at answering them:

• Why not read the info pages, which contains more details?
• some people finds it easier to watch movies than reading static text.
• screencast-mode displays the capabilities of a mode, instead of describing them.
• those who just need to know how to use a mode doesn't need all the details of the info-page.
• If videos are superior, why not just create a regular video?
• a video is static, it's hard to change it if you discover an error - you'll have to do it in one take unless you got some video editing software.
• the screencast sources can be edited by others, inviting collaboration (also it's a lot smaller size-wise)
• the screencast will tell the user if his Emacs is configured right to use the feature it explains

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