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The text classes included in the AutoFitText package automatically set their font size to fill up their available space without truncation. Provide explicit dimensions to fit an exact area.

Creating the AutoFitText components

The package includes 3 components: (1) The AutoFitRichText that extends the Spark RichText component, (2) the AutoFitLabel that extends the Spark Label component, and (3) the AutoFitFTETextField that extends the Spark FTETextField component.

Using the AutoFitText component

All of the components will fit the available space automatically, even when resized.

Fitting Process

Fitting works by using a recursive function to locate a non-truncating size. The "maxFontSize" and "minFontSize" properties determine the start and end bounds of the search.

Performance Considerations

Reduce the space between the "maxFontSize" and "minFontSize" to increase performance. E.G. if it is known that the desired text size will be within 10 - 20 pixels, then set the min/max to 10 to 20 to decrease the fit time.

The number of line breaks cannot exceed the number of words. This is to prevent the default behaviour that may split one long word into multiple lines. Also, small words should not be wrapped. Use the "ignoreWordLength" property to skip small length words in the word count. The default is to not count words less than 4 characters in length.

The "precisionThreshold" property is used to determine when the fit is 'good enough', measured in font pixel size. Higher values will increase performance but not fit as optimally.

Measured Dimensions

Since the components fit the available space, measured dimensions have no purpose or meaning so developers should not rely on them for layout.


Scaling will not work because the entire component will scale, not just the text.


Slower than the AutoFitLabel and the AutoFitFTETextField but supports the Text Layout Framework ("TLF").

RichText does a better job of not wrapping intra-word than the Label via support for the "breakOpportunity" style which is set by default to "auto".


Faster than the AutoFitRichText component, but since the Spark Label does not support TLF, intra-word wrapping cannot be stopped via the "breakOpportunity" style.


AutoFitFTETextfield is very fast. Much, much faster than the AutoFitLabel or AutoFitRichText, but it does not implement IVisualElement so it can only be added to DisplayObjectContainers. Also, AutoFitFTETextfield instances do not participate in layout or CSS, so any changes in size/position/styling need to be accomplished manually in the parent and parent layout. Also, the fitText() method must be called manually because it will not be called in response to size changes.

Therefore, the primary purpose of the AutoFitFTETextField is as a label in an item renderer extending UIComponent. The focus is on performance and not simplicity.

The parent must call the fitText() method manually when any relevant property changes.

Since the FTETextField does not support TLF, intra-word wrapping cannot be stopped via the "breakOpportunity" style. RichText does support the "breakOpportunity" style.

See the TreeMap demo for an example of large numbers of AutoFitFTETextField components.

Intra-word Line Breaks

If there is a problem, use the AutoFitRichText component.


See the AutoFitText demo application for example code.

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