Hi,

I have attached a minor mode for emacs 21 that dynamically filters out 
stuff that is indented. It is a bit similar to hideshow, hidelines and 
outline, but it works on the indentation level instead of the semantics 
of some programming language. The mode is slow with very large files, 
because I couldn't figure out how to check if the point is in the 
visible region of the buffer. Also, the only way I could detect that the 
point had moved was by saving the point position and checking if it has 
changed in the post-command-hook.

The question is, what is the right way to check that the point has 
moved? How do I know if the point is in the visible region of the buffer?

juha