photoshop text overflow

I've solved a related problem in doing contact sheet thumbnail captions. In my case, I know the bounds of the caption and need to fit the name of the image in that bounds. If I can't scale it to fit, I truncate it and append '...' until it fits. The performance is not what I would like, but it's not unreasonable.

ContactSheetII.prototype.insertCaption = function(doc, csOpts, bnds, file,  image) {
  var self = this;
  if (file == undefined) {
    file = File(image.name);
  }
  var caption = decodeURI(file.name);
  if (csOpts.captionFilename) {
    if (csOpts.noExtensions) {
      caption = file.strf("%f");
    }
  } else {
    caption = '';
  }
//   LogFile.write("Inserting caption " + caption + " at " + bnds);
  app.activeDocument = doc;
  var layer = doc.artLayers.add();
  layer.kind = LayerKind.TEXT;
  layer.name = decodeURI(file.name);
  var titem = layer.textItem;
  if (csOpts.autoscaleCaptions) {
    titem.minimumGlyphScaling = 50;
    titem.desiredGlyphScaling = 100;
  }
  titem.contents = caption;
  if (!csOpts._fontColor) {
    csOpts._fontColor = psx.colorFromString(csOpts.fontColor);
  }
  titem.color = csOpts._fontColor;
  titem.size = csOpts.fontSizePX;
  titem.font = csOpts.font;
  titem.kind = TextType.PARAGRAPHTEXT;
  var captionWidth = bnds[2]-bnds[0];
  // Check to see if the caption is too wide
  var twidth = Math.round(titem.width);
  if (csOpts.autoscaleCaptions) {
    // try to scale the glyph width to make it fit
    if (twidth > captionWidth) {
      if ((captionWidth / twidth) > 0.5) {
        titem.desiredGlyphScaling = (100 * captionWidth) / twidth;
      } else {
        titem.desiredGlyphScaling = 50;
      }
    }
    // switching the kind forces PS to recompute the text size
    titem.kind = TextType.POINTTEXT;
    titem.kind = TextType.PARAGRAPHTEXT;
    twidth = Math.round(titem.width);
  }
  if (csOpts.dotTruncate) {
    // truncate the text until it fits
    if (twidth > captionWidth) {
      if (caption.length <= 4) {
        // handle the deviant case here
        titem.contents = caption[0] + '...';
      } else {

        // estimate the string length...
        var len = Math.round((captionWidth/twidth) * caption.length);
        var str = caption.substring(0, len-4) + '...';
        // take off the file extension first
        while (twidth > captionWidth+4) {
          titem.contents = str;
          if (str.length <= 4) {
            break;
          }
          titem.kind = TextType.POINTTEXT;
          titem.kind = TextType.PARAGRAPHTEXT;
          twidth = Math.round(titem.width);
          
          str = str.substring(0, str.length-4) + '...';
        }
      }
    }
  }
  titem.justification = Justification.CENTERJUSTIFIED;
  titem.width = bnds[2]-bnds[0];
  titem.position = [bnds[0], bnds[1]];
  var style = csOpts.captionStyle;
  if (style && style != CSII.NO_CAPTION_STYLE) {
    layer.applyStyle(style);
  }
  return layer;
};