Open Shell Vista Taskbar

[Gauthier Zitnik]

TheQuick Launch bar, available in versions of Windows earlier than Windows 7, contains shortcuts to applications. Windows provides default entries, such as Windows Internet Explorer, and the user can add any further shortcuts that they choose. Icons in this area respond to a single click. In Windows 7 and later, this functionality is included in the taskbar buttons.

Applications can put icons in the notification area to indicate the status of an operation or to notify the user about an event. For example, an application might put a printer icon in the notification area to show that a print job is under way. However, in Windows 7 and later, some of the information previously provided by the notification area should be provided through an application's taskbar button. The notification area is located at the right edge of the taskbar (if the taskbar is horizontal) or at the bottom (if the taskbar is vertical). For more information, see Notifications and the Notification Area.

The user can right-click the taskbar to display the shortcut menu. The shortcut menu includes commands to cascade windows, stack windows, show windows side-by-side, show the desktop, start Task Manager, and set taskbar properties. The shortcut menu also provides the option to add or remove a set of toolbars from the taskbar. You can add new toolbars to this menu by registering them under the CATID_DeskBand category. For more information, see Implementing Band Objects. Note that as of Windows 7, the taskbar and the notification area have separate shortcut menus. These shortcut menus share some options, such as window arrangement, and add others.

The taskbar supports two display options: Auto-Hide and, in Windows Vista and earlier only, Always On Top (the taskbar is always in this mode in Windows 7 and later). To set these options, the user must open the taskbar shortcut menu, click Properties, and select or clear the Auto-hide the taskbar check box or the Keep the taskbar on top of other windows check box. To retrieve the state of these display options, use the ABM_GETSTATE message. If you would like to be notified when the state of these display options changes, process the ABN_STATECHANGE notification message in your window procedure. To change the state of these display options, use the ABM_SETSTATE message.

The work area is the portion of the screen not obscured by the taskbar. To retrieve the size of the work area, call the SystemParametersInfo function with the SPI_GETWORKAREA value set. To retrieve the rectangle coordinates that describe the location of the taskbar, use the ABM_GETTASKBARPOS message.

It is possible to cover the taskbar by explicitly setting the size of the window rectangle equal to the size of the screen with SetWindowPos. For Windows 2000 systems or later, the window must lack either WS_CAPTION or WS_THICKFRAME, or else the window must be sized so that the client area covers the entire screen. Also particular to those systems, if the taskbar is set to Always On Top, it will remain hidden only while the application is the foreground application.

The Shell creates a button on the taskbar whenever an application creates a window that isn't owned. To ensure that the window button is placed on the taskbar, create an unowned window with the WS_EX_APPWINDOW extended style. To prevent the window button from being placed on the taskbar, create the unowned window with the WS_EX_TOOLWINDOW extended style. As an alternative, you can create a hidden window and make this hidden window the owner of your visible window.

The Shell will remove a window's button from the taskbar only if the window's style supports visible taskbar buttons. If you want to dynamically change a window's style to one that does not support visible taskbar buttons, you must hide the window first (by calling ShowWindow with SW_HIDE), change the window style, and then show the window.

If you want your application to get the user's attention when the window is not active, use the FlashWindow function to let the user know that a message is waiting. This function flashes the window button. Once the user clicks the window button to activate the window, your application can display the message.

Version 4.71 and later of Shell32.dll adds the capability to modify the contents of the taskbar. From an application, you can now add, remove, and activate taskbar buttons. Activating the item does not activate the window; it shows the item as pressed on the taskbar.

The taskbar modification capabilities are implemented in a Component Object Model (COM) object (CLSID_TaskbarList ) that exposes the ITaskbarList interface (IID_ITaskbarList). You must call the ITaskbarList::HrInit method to initialize the object. You can then use the methods of the ITaskbarList interface to modify the contents of the taskbar.

Use the Shell_NotifyIcon function to add, modify, or delete icons from the notification area. The dwMessage parameter of Shell_NotifyIcon is a message to the taskbar that specifies the action to be taken. The pnid parameter is a pointer to a NOTIFYICONDATA structure that is used to identify the icon and pass any additional information that is needed for the system to process the message.

When you have completed a user interface operation, return focus to the notification area by calling Shell_NotifyIcon with dwMessage set to NIM_SETFOCUS. For example, you could do this when a taskbar icon displays a shortcut menu, but the user cancels it by pressing the ESCAPE key.

Applications commonly put icons in the notification area of the taskbar to serve as status indicators. You can provide additional information when the user performs mouse actions, such as moving the mouse pointer over the icon or clicking the icon.

The system notifies you of mouse and keyboard events by sending an application-defined callback message that is associated with a particular icon. In this way, the system can notify an application when the user, for instance, clicks the icon or selects it by pressing a key.

You define an icon's callback message when you add the icon to the taskbar. The callback message identifier is specified in the uCallbackMessage member of the NOTIFYICONDATA structure passed with NIM_ADD. When an event occurs, the system sends the callback message to the window procedure of the window specified by the hWnd member. The wParam parameter of the message contains the identifier of the taskbar icon in which the event occurred. The lParam parameter holds the mouse or keyboard message associated with the event. For example, when the mouse pointer moves onto a taskbar icon, lParam contains WM_MOUSEMOVE.

Typically, clicking the icon causes the application to display a window with additional information, right-clicking displays a shortcut menu, and double-clicking executes the default shortcut menu command.

Versions 5.0 and later of the Shell handle Shell_NotifyIcon mouse and keyboard events in different ways than earlier Shell versions found on Windows NT 4.0, Windows 95, and Windows 98. The differences are as follows:

You can select which way the Shell should behave by calling Shell_NotifyIcon with dwMessage set to NIM_SETVERSION. Set the uVersion member of the NOTIFYICONDATA structure to indicate whether you want version 5.0 or pre-version 5.0 behavior.

With Microsoft Internet Explorer 4.0 and later, the Shell notifies applications that the taskbar has been created. When the taskbar is created, it registers a message with the TaskbarCreated string and then broadcasts this message to all top-level windows. When your taskbar application receives this message, it should assume that any taskbar icons it added have been removed and add them again. This feature generally applies only to services that are already running when the Shell launches. The following example shows a very simplified method for handling this case.

You add an icon to the taskbar notification area by filling in a NOTIFYICONDATA structure and then passing the structure to Shell_NotifyIcon with dwMessage set to NIM_ADD. The structure members must specify the handle to the window that is adding the icon, as well as the icon identifier and icon handle. You can also specify tooltip text for the icon. If you need to receive mouse messages for the icon, specify the identifier of the callback message that the system should use to send the message to the window procedure.

If you specify a callback message for a taskbar icon, the system sends the message to your application whenever a mouse event occurs in the icon's bounding rectangle. The wParam parameter of the message specifies the identifier of the taskbar icon, and the lParam parameter of the message specifies the message that the system generated as a result of the mouse event.

The function in the following example is from an application that adds both battery and printer icons to the taskbar. The application calls the function when it receives a callback message. The function determines whether the user has clicked one of the icons and, if a click has occurred, calls an application-defined function to display status information.

Since @Mr. Fox showed an interest in these customization in a different thread and mentioned how others might also like to know, figured i'd write a little guide. Also figured this could be a combo thread for those who would like to show off their Windows specific themes/customizations and overlays etc.

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