Adobe 38039481 User Guide - Page 486

FLASH CS3 480 User Guide Note: Do not type a description in the Description field of the Accessibility panel for instances (such as text) that the screen reader reads aloud. See also "Using Flash to enter accessibility information for screen readers" on page 355 Using color You must make decisions about using colors in an accessible file. You must not rely only on color to communicate particular information or directives to users. A color-blind user cannot operate a page if it asks to click on the blue area to launch a new page or the red area to hear music. Offer text equivalents on the page or in an alternate version to make your site accessible. Also, check that significant contrast exists between foreground and background colors to enhance readability. If you place light gray text on a white background, users cannot easily read it. Similarly, small text is difficult for many visitors to read. Using high-contrast and large or resizable text benefits most users, even those without impairments. Ordering, tabbing, and the keyboard Reading order and tabbing are important considerations for making accessible Flash websites. When you design an interface, the order that it appears on the page might not match the order in which the screen reader describes each instance. You can control and test reading order, as well as control tabbing in the SWF file. Controlling reading order The default reading order is not predictable and does not always match the placement of your assets or the visual layout of the page. Keeping the layout simple can help create a logical reading order without using ActionScript. However, you have more control over reading order if you use ActionScript and test the reading order in your SWF files. Important: Do not miss ordering a single instance in your SWF file, or the reading order reverts to the default (and unpredictable) reading order. Controlling tabbing and content Visitors who rely on screen readers to describe a site's content typically use tabbing and keyboard controls to navigate the operating system and web pages, because using the mouse is not useful when the screen cannot be seen. Use the tabIndex and tabEnabled properties with the movie clip, button, text field, or component instances to offer intelligent tabbing control in accessible SWF files. In addition to tabbing, you can use any key-press actions to navigate through the SWF file, but you must communicate that information using the Accessibility panel. Use the Key class in ActionScript to add key-press scripts to the SWF file. Select the object for which you want to use the key-press script, and add the shortcut key in the Shortcut field on the Accessibility panel. Add keyboard shortcuts to essential and frequently used buttons in your SWF file. Note: In ActionScript 3.0, tabIndex and tabEnabled are properties of the InteractiveObject class. In ActionScript 2.0, they do not require a class reference. Note: Avoid invisible buttons in accessible SWF files, because screen readers do not recognize these buttons. (Invisible buttons are buttons for which you define only a hit area, the clickable region, for the button.) Many SWF files have a rapid succession of information, and screen readers frequently cannot keep up with this pace. Provide controls for the SWF file, letting the user use buttons to navigate through the file at their own pace, and letting them pause the process if necessary.