is it possible in a script to target a specific comp layer without having that comp selected in the project window ?

[Xavier Gomez]

The After Effects scripting guide has a very loosy description of app.project.activeItem.
If you follow it, you might think it is only determined by the panel selection, but it’s not.

It seems to be determined in this order:

if the Project Panel is active, then it is the unique selected item in that Panel, or null.
if the Project Panel is not active, then it is the front comp in the Timeline Panel if any, or null again.

(paradoxally, viewers dont play a role, you can have all viewers closed and no project selection, and still have a comp “active”: the one in front in the timeline panel).

So you can do this:

var X = app.project.activeItem;
if (X instanceof CompItem && !X.selected){
// X is the comp in front in the timeline
}
else{
// stuck
};

If you have CS6 or later, you can do this prior to querying activeItem:

if (app.activeViewer!=null && (app.activeViewer.type==ViewerType.VIEWER_COMPOSITION)){
app.activeViewer.setActive();
// at this stage, app.project.activeItem is necessarily the front comp in the timeline panel
var comp = app.project.activeItem;
var layers = comp.selectedLayers;
}
else{
// ask to activate a comp
};

Xavier

[Dirk De jong]

Thanks very much for the quick reply and useful suggestions. I’ll give these things a try.