Setting filenames and opening files

[pbristow]

Hi all, I have a few questions for anyone who is familiar with the internals of AVIsynth. Not urgent. Consider this a moment of light relief from your intensive hacking and modding duties.

Q1) If I write a script such as:

Filename = "text" + ".avi"
AVIsource(Filename)

...and invoke it via VirtualDub, at what point does the value "text.avi" get assigned to the variable Filename? Is it during the instantiation of avisynth, when plugins etc. are loaded? Or is it when the controlling application (VDub or whatever) asks for its first frame to be served, and AVIsource is called for the first time, realises it needs a filename, and triggers the evaluation of the preceding line?


Q2) What I'm working around to is the following idea: Suppose I (or someone else) wrote a function or a plug-in that prompts the user for a filename/path (via a standard Windows-style file selector) and then returns that filename/path, and used it as follows:

Filename = SelectFile()
AVIsource(Filename)

When would the user see the filename prompt? Would it pop up as soon as the avisynth script was loaded, or only once the calling app demanded the first frame of video (e.g. when they pressed "play" on a player)?


Q3) Has anyone ever written such a file-selector plug-in, or thought of adding such a function to Avisynth itself?


Cheers.