This is an old thread, but came up with another question. To speed up my scripts to avoid redraws, I use code to turn on and off action steps:
//function to set action playback to step by step so the screen refreshes when a dialog box comes up
function setActionToStep(){
var idsetd = charIDToTypeID( "setd" );
var desc1 = new ActionDescriptor();
var idnull = charIDToTypeID( "null" );
var ref1 = new ActionReference();
var idPrpr = charIDToTypeID( "Prpr" );
var idPbkO = charIDToTypeID( "PbkO" );
ref1.putProperty( idPrpr, idPbkO );
var idcapp = charIDToTypeID( "capp" );
var idOrdn = charIDToTypeID( "Ordn" );
var idTrgt = charIDToTypeID( "Trgt" );
ref1.putEnumerated( idcapp, idOrdn, idTrgt );
desc1.putReference( idnull, ref1 );
var idT = charIDToTypeID( "T " );
var desc2 = new ActionDescriptor();
var idperformance = stringIDToTypeID( "performance" );
var idperformance = stringIDToTypeID( "performance" );
var idstepByStep = stringIDToTypeID( "stepByStep" );
desc2.putEnumerated( idperformance, idperformance, idstepByStep );
var idPbkO = charIDToTypeID( "PbkO" );
desc1.putObject( idT, idPbkO, desc2 );
executeAction( idsetd, desc1, DialogModes.NO );
}//end function
// function to return action to accelerated mode - no refresh of screen for each step.=======================================================
function setActionToAcc(){
var idsetd = charIDToTypeID( "setd" );
var desc3 = new ActionDescriptor();
var idnull = charIDToTypeID( "null" );
var ref2 = new ActionReference();
var idPrpr = charIDToTypeID( "Prpr" );
var idPbkO = charIDToTypeID( "PbkO" );
ref2.putProperty( idPrpr, idPbkO );
var idcapp = charIDToTypeID( "capp" );
var idOrdn = charIDToTypeID( "Ordn" );
var idTrgt = charIDToTypeID( "Trgt" );
ref2.putEnumerated( idcapp, idOrdn, idTrgt );
desc3.putReference( idnull, ref2 );
var idT = charIDToTypeID( "T " );
var desc4 = new ActionDescriptor();
var idperformance = stringIDToTypeID( "performance" );
var idperformance = stringIDToTypeID( "performance" );
var idaccelerated = stringIDToTypeID( "accelerated" );
desc4.putEnumerated( idperformance, idperformance, idaccelerated );
var idPbkO = charIDToTypeID( "PbkO" );
desc3.putObject( idT, idPbkO, desc4 );
executeAction( idsetd, desc3, DialogModes.NO );
}//end function