ActionScript for Flash MX: The Definitive Guide, Second Edition

TextField.type Property

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depending on font size, case, and even the intrinsic width of the character itself. For

example, in 12-point Times New Roman:

• The character “a” has a width of 5.

• The character “A” has a width of 9.

• The character “i” has a width of 3.

• The character “w” has a width of 9.

When the

autoSize property is true, textWidth is always 4 pixels less than _width, leaving a

small gutter between the field’s longest line of text and the right and left borders.

To determine the width of a string before assigning it to a text field, use TextFormat.

getTextExtent().

Example

The textWidth property can be used to create horizontal scrolling interfaces or to scale

graphic elements to match the size of a line of text. The following code creates a text field

and then draws a line above the field that matches its text’s width. Notice that the gutter is

accommodated by the line-width calculation:

// Create the text field

this.createTextField("theField_txt", 1, 0, 0, 200, 20);

theField_txt.text = "Welcome to my web site";

theField_txt.autoSize = true;

// Set the line thickness

this.lineStyle(3);

// Position the start point

this.moveTo(theField_txt._x + 2, theField_txt._y);

// Draw the line to the end point

this.lineTo(theField_txt._x + theField_txt.textWidth, ...