Status Bars

It has become common, even expected, for Windows applications to include status bars that display context-sensitive help for toolbar buttons and menu items. SDK-style Windows applications customarily display descriptive help text for menu items by trapping WM_MENUSELECT messages and updating the status bar. MFC provides an easier way. When a CStatusBar is connected to a frame window, it automatically displays a string of help text when a menu item is highlighted. If the application includes a toolbar, and if the toolbar style includes a CBRS_FLYBY flag, the status bar also displays flyby text for toolbar buttons. The best part is that all you're responsible for besides creating and initializing the status bar (something that requires just a few lines of code) is providing the help text in the form of string resources in your application's RC file. The framework does the rest.

Status bars can do much more than just display help text, of course. A status bar can be divided into one or more areas that are variously referred to as panes, panels, or indicators. The text of each pane can be set individually, so one pane can display the current line number or page number in a document while another displays menu and toolbar help and still others display the current Caps Lock and Num Lock states. Some status bars even contain progress controls that report percentage-complete figures for potentially lengthy operations such as document saving and loading.

Creating and Initializing a Status Bar

In MFC, a status bar is an instance of CStatusBar. An application that uses a status bar typically declares a CStatusBar object as a member of the frame window class. Then the frame window's OnCreate handler creates the status bar with a statement like this one:

m_wndStatusBar.Create (this);

The lone argument passed to Create identifies the status bar's parent window. Passing a this pointer referring to a frame window makes the status bar a child of the frame window. A status bar created in this way doesn't need to be destroyed before the application terminates because it's destroyed automatically when its parent is destroyed. CStatusBar::Create also accepts parameters specifying the status bar's style and child window ID, but the default values MFC provides for these parameters do quite nicely for most applications.

After it's created, a status bar is initialized by calling CStatusBar::SetIndicators. SetIndicators specifies the number of panes the status bar will contain and optionally assigns string resources to individual panes. The statements

UINT nIndicator = ID_SEPARATOR;m_wndStatusBar.Create (this);m_wndStatusBar.SetIndicators (&nIndicator, 1);

create a simple status bar containing just one pane. ID_SEPARATOR is a generic ID that says no string resource is associated with this pane. You can create a simple "binary" pane that indicates whether a particular feature of your application is on or off by specifying a string resource ID instead of ID_SEPARATOR and connecting the pane to an update handler that uses CCmdUI::Enable to enable and disable the pane. An enabled pane displays the string resource assigned to it, but a disabled pane is blank. The status bar created by the following code sample includes a pane that displays the text string "INS" when the application is in ins

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