Supporting the ShowSounds Flag
To convey complex information to users who cannot rely on audible forms, the computer industry has standardized a concept called "ShowSounds." ShowSounds is a global flag that can be set by the user to indicate that he or she needs important information displayed by visual means. It requests applications to display the equivalent of closed captions for their sounds.
Applications can check the ShowSounds flag by calling the SystemParametersInfo function with the SPI_GETSHOWSOUNDS value.
Use of the ShowSounds flag does not mean that sounds cannot be presented normally. In fact, redundant use of sound and visuals generally increases the usability of an application. The user should be able to request visual feedback independently of whether they want audible feedback.
The ShowSounds flag is only applicable to applications that would normally present important information by sound alone. The application is responsible for determining how to convey the information in visual form. Examples in the following sections can help you determine behavior appropriate to your situation.
Audible alerts
To attract the user's attention, such as when new email arrives, an application might use the following techniques:
- Flash its title bar by using the FlashWindow function. If the window is not visible, the function will automatically flash the application's button on the taskbar.
- Display a message box that acquires the activation and keyboard focus. This technique should be avoided if the user might be typing into another application at the time.
- Display a status indicator on the notification area of the taskbar. This indicator should also flash when initially displayed to help attract the user's attention.
Redundant sounds
Applications often make a sound to indicate an error status — for example, when the user types an invalid character. In these cases, the application might flash its title bar by using the FlashWindow function. If the window is not visible, it will automatically flash the application's button on the taskbar.
Playing a video clip
Applications that display multimedia animation of video clips should support the ShowSounds flag with true closed captioning. Microsoft Video for Windows supports creating a separate, synchronized data stream for captioning information, although the application is responsible for displaying the information on the screen. Captioning is only necessary if the video clip has an audio track containing important information.
Playing an audio wave file
Applications that play audio wave files containing important information should display closed captions for that information. However, it may be difficult in some cases to synchronize the captions with the audio. For brief wave files, the captions can be displayed in a status bar or elsewhere in the application window, or in a floating window similar to a tool tip control. Longer descriptions can be displayed in a separate window. The user should be able to scroll through the information at his or her own pace. In hypertext applications, a link can be used to take the user to a separate screen containing the textual descriptions.