Overlay icons are intended to supply important, long-standing status or notifications such as network status, messenger status, or new mail. The application designer must decide during the development cycle which method-icon overlay or notification area status icon-best serves that application. Icon overlays serve as a contextual notification of status, and are intended to negate the need for a separate notification area status icon to communicate that information to the user. The following illustration shows an overlay (the small, green square that indicates the user status as "Available") applied to the far-right taskbar button. These overlays are similar to existing overlays used for shortcut icons or security notifications, displayed at the lower-right corner of the button.
The Windows 7 taskbar allows an application to provide that same sort of user feedback through its taskbar button, centralizing more of the application information in one place. In versions of Windows earlier than Windows 7, applications often used icons in the notification area of the taskbar to display application status and notifications to the user. Otherwise, it returns an HRESULT error code. If this method succeeds, it returns S_OK. This can generally be done after you call SetOverlayIcon because the taskbar makes and uses its own copy of the icon.Ī pointer to a string that provides an alt text version of the information conveyed by the overlay, for accessibility purposes. It is the responsibility of the calling application to free hIcon when it is no longer needed.
How a NULL value is handled depends on whether the taskbar button represents a single window or a group of windows. If an overlay icon is already applied to the taskbar button, that existing overlay is replaced. This should be a small icon, measuring 16x16 pixels at 96 dpi. The handle of an icon to use as the overlay.
This handle must belong to a calling process associated with the button's application and must be a valid HWND or the call is ignored. The handle of the window whose associated taskbar button receives the overlay. ITaskbarList3::SetOverlayIcon method (shobjidl_core.h)Īpplies an overlay to a taskbar button to indicate application status or a notification to the user.
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