Altering font size to fit the field size -- Flash CS3

Given a width in pixels and a maximum number of lines to display, the HeadlineTextField alters the font size to make the text fit the field. If the text is short the font size will be very large, creating a tabloid-style headline. If the text is long the font size will of course be smaller.

public function fitText(msg:String, maxLines:uint = 1, toUpper:Boolean = false, targetWidth:Number = -1):uint
{
    this.text = toUpper ? msg.toUpperCase() : msg;
    
    if (targetWidth == -1)
    {
        targetWidth = this.width;
    }
    
    var pixelsPerChar:Number = targetWidth / msg.length;
    
    var pointSize:Number = Math.min(MAX_POINT_SIZE, Math.round(pixelsPerChar * 1.8 * maxLines));
    
    if (pointSize < 6)
    {
        // the point size is too small
        return pointSize;
    }
    
    this.changeSize(pointSize);
    
    if (this.numLines > maxLines)
    {
        return shrinkText(--pointSize, maxLines);
    }
    else
    {
        return growText(pointSize, maxLines);
    }
}

public function growText(pointSize:Number, maxLines:uint = 1):Number
{
    if (pointSize >= MAX_POINT_SIZE)
    {
        return pointSize;
    }
    
    this.changeSize(pointSize + 1);
    
    if (this.numLines > maxLines)
    {
        // set it back to the last size
        this.changeSize(pointSize);
        return pointSize;
    }
    else
    {
        return growText(pointSize + 1, maxLines);
    }
}

public function shrinkText(pointSize:Number, maxLines:uint=1):Number
{
    if (pointSize <= MIN_POINT_SIZE)
    {
        return pointSize;
    }
    
    this.changeSize(pointSize);
    
    if (this.numLines > maxLines)
    {
        return shrinkText(pointSize - 1, maxLines);
    }
    else
    {
        return pointSize;
    }
}

The HeadlineTextField.fitText() method uses a simple recursive technique to size the font. First it guesses an average number of pixels per character in the text and from there calculates a starting point size. Then it changes the text field's font size and checks whether the text has word wrapped to create more than the maximum number of text lines. If there are too many lines it calls the shrinkText() method to decrease the font size and try again. If there are not too many lines it calls the growText() method to increase the font size and try again. The process stops at the point where incrementing the font size by one more point would create too many lines.