What why and when charIDToTypeID ?

As c.pfaffenbichler said, 4 chars strings are converted via charIDToTypeID to numbers. In effect "save" is easier to remember than 1935767141.

typeIDs are used in ActionManager code (have a look at it in the log of the ScriptingListener plugin), which is an alternative way to drive Photoshop - that is, without using the DOM.

Everything you can do with the DOM, you can reply via AM - not the reverse, though.

Even more user friendly that charID are, in my opinion, stringIDs.

For instance, while "save" is meaningful, "#Rlt" not so (it's "distanceUnit", as a stringID).

A charIDToStringID function can be implemented easily:

var c2s = function(charID) { return app.typeIDToStringID(app.charIDToTypeID(charID)) };

As follows for instance the default output of the ScriptingListener for the PS "File - New" command:

// =======================================================
var idMk = charIDToTypeID( "Mk  " );
    var desc78 = new ActionDescriptor();
    var idNw = charIDToTypeID( "Nw  " );
        var desc79 = new ActionDescriptor();
        var idpreset = stringIDToTypeID( "preset" );
        desc79.putString( idpreset, """Default Photoshop Size""" );
    var idDcmn = charIDToTypeID( "Dcmn" );
    desc78.putObject( idNw, idDcmn, desc79 );
executeAction( idMk, desc78, DialogModes.NO );
// =======================================================

which can be rewritten as:

var d1 = new ActionDescriptor();
var d2 = new ActionDescriptor();
d2.putString( s2t("preset"), "Default Photoshop Size" );
d1.putObject( s2t("new"), s2t("document"), d2 );
executeAction( s2t("make"), d1, DialogModes.NO);

and it's possibly a bit more readable by humans ;-)

Davide Barranca

www.davidebarranca.com

Quote from the Object Model Viewer:

Converts from a four character code to a runtime ID.

I think the character IDs were introduced to make things easier as they should be more easy to remember than the corresponding numbers.