Scaling Label text size to fit available area

Working with text in Flex 3 can be difficult. Especially if you want to scale text to fit an area (a task I recently discovered was not intuitive at all). Should you scale the text control? Convert the contents to a bitmap and resize it? Set the fontSize and test it’s width against the parent container?

The cleanest solution I found was to use was to compare the textWidth property of the Label against the parent container’s width (the available area), and then scale the Label component based on that comparison.

Here’s the running example (the default font size is 36 pts, but you can see that the second and third labels are scaled according to how much text is in the Label):

There’s a bit of a caveat to this, which is that in general, this will not be a “UI best practice”. A list of text items, where the text varies in size for each item in the list, is not the most readable or user friendly way to present information.

The main app and custom component files are below, but here’s a few lines to show you how it’s done.

In the Label tag, trigger a function on the creationComplete event:

<mx:Label id="myLabel"
x="101" y="22"
fontSize="36"
text="{title}"
width="100%" truncateToFit="false"
creationComplete="scaleLabelToFit()"
/>

You should also set truncateToFit to false so that a Label whose text comes close to the edge does not get truncated.

The scaleLabelToFit() function calculates the ratio of the main component’s width to the width of the Label’s text (textWidth):

var ratio:Number = ((this.width - myImage.width) - 10) / myLabel.textWidth;

This line subtracts the width of the image and an additional 10 pixels to account for padding.

Then, if the ratio is less than 1, scale the text control. If the ratio were greater than 1, you would not want to scale the text up, so just ignore that case.

if (ratio < 1) {
myLabel.scaleX = ratio;
myLabel.scaleY = ratio;
}

That’s it. Here’s a ZIP of the entire app, including images:

ScaleLabelSizes.zip