Script : How to add a progress bar to XMP Writing script ?

The free ScriptUI for dummies pdf by Peter Kahrel has a section on creating progress bars, and in general is extremely useful for understanding how to make UIs for adobe program scripts.

You can download it from here: http://www.kahrel.plus.com/indesign/scriptui.html

I am using this progress bar on bridge. I don't remember who gave it to me time ago.

Anyway I have adapt it to your script:

#target bridge  

if( BridgeTalk.appName == "bridge" ) { 

descToTitle = MenuElement.create("command", "Log Comment to Description", "at the end of Tools");

}

descToTitle.onSelect = function () {

    if (ExternalObject.AdobeXMPScript == undefined) ExternalObject.AdobeXMPScript = new ExternalObject("lib:AdobeXMPScript");

    var thumb = app.document.selections;

    //

    var progBar = new createProgressWindow("Work in Progress", "Please wait", false);

    for (var s in thumb) {

        if(thumb.hasMetadata) {

            var selectedFile = thumb.spec;

            var myXmpFile = new XMPFile( selectedFile.fsName, XMPConst.UNKNOWN, XMPConst.OPEN_FOR_UPDATE);

            var myXmp = myXmpFile.getXMP();

            var LogComment = myXmp.getProperty(XMPConst.NS_DM, "logComment");

            myXmp.deleteProperty(XMPConst.NS_DC, "description");

            myXmp.appendArrayItem(XMPConst.NS_DC, "description", LogComment, 0, XMPConst.ALIAS_TO_ALT_TEXT);

            myXmp.setQualifier(XMPConst.NS_DC, "description[1]", "http://www.w3.org/XML/1998/namespace", "lang", "x-default");

        }

        //

        progBar.updateProgress (Math.floor((Number(s)+1)*(100/thumb.length)), "Waiting, " + Math.floor((Number(s)+1)*(100/thumb.length)) + "% completed.");

        //

        if (myXmpFile.canPutXMP(myXmp)) {

            myXmpFile.putXMP(myXmp);

            myXmpFile.closeFile(XMPConst.CLOSE_UPDATE_SAFELY);

        } else {

            xmpFile.closeFile();

        }

    }

}

//////////////

function createProgressWindow(title, message, hasCancelButton) {

    var win;

    if (title == null) title = "Work in progress";

    if (message == null) message = "Please wait...";

    if (hasCancelButton == null) hasCancelButton = false;

    win = new Window("palette", "" + title, undefined);

    win.bar = win.add("progressbar", {x: 20,y: 12,width: 300,height: 20}, 0, 100);

    win.stMessage = win.add("statictext", {x: 10,y: 36,width: 320,height: 20}, "" + message);

    win.stMessage.justify = 'center';

    if (hasCancelButton) {

        win.cancelButton = win.add('button', undefined, 'Cancel');

        win.cancelButton.onClick = function() {

            win.close();

            throw new Error('User canceled the pre-processing!');

        }

    }

    this.reset = function(message) {

        win.bar.value = 0;

        win.stMessage.text = message;

        return win.update();

    }

    this.updateProgress = function(perc, message) {

        if (perc != null) {

            win.bar.value = perc;

        }

        if (message != null) {

            win.stMessage.text = message;

        }

    return win.update();

    }

    this.close = function() {

        return win.close();

    }

    win.center(win.parent);

    return win.show();

}