As a Windows user, you’re accustomed to seeing controls such as buttons, list boxes, menus, and edit boxes. As Windows developed, however, Microsoft noticed that developers routinely create other types of controls in their programs: toolbars, status bars, progress bars, tree views, and others. To make life easier for Windows programmers, Microsoft included these popular controls as part of the operating environment of Windows 95 (as well as later versions of Windows NT and then Windows 98). Now Windows programmers no longer need to create from scratch their own versions of these controls. This unit introduces you to many of the 32-bit Windows common controls.

This Unit’s sample program is called Common. It demonstrates seven of the Windows 95 common controls: the progress bar, up-down, list view, tree view, rich edit,date picker, and month calendar controls, all of which are shown in Figure 8.1. In the following sections, you learn the basics of creating and using these controls in your own applications.

FIG. 8.1 The Common sample application demonstrates nine Windows 95 common controls.

To make Common, create a new project with AppWizard and name it Common. Choose a single-document interface (SDI) application in Step 1 and accept all the defaults until Step 6. Drop down the Base Class box and choose CScrollView from the list. This ensures that users can see all the controls in the view, even if they have to scroll to do so. Click Finish and then OK to complete the process.

The controls themselves are declared as data members of the view class. Double-click CCommonView in ClassView to edit the header file and add the lines in Listing 8.1 in the Attributes section. As you can see, the progress bar is an object of the CProgressCtrl class. It’s discussed in the next section, and the other controls are discussed in later sections of this Unit.

Expand the CCommonView class. Double-click CCommonView::OnDraw() in ClassView and replace the TODO comment with these lines:

These label the controls that you will add to CCommonView in this Unit.

The common control that’s probably easiest to use is the progress bar, which is nothing more than a rectangle that slowly fills in with colored blocks. The more colored blocks that are filled in, the closer the task is to being complete. When the progress bar is completely filled in, the task associated with the progress bar is also complete. You might use a progress bar to show the status of a sorting operation or to give the user visual feedback about a large file that’s being loaded.

Before you can use a progress bar, you must create it. Often in an MFC program, the controls are created as part of a dialog box. However, Common displays its controls in the application’s main window, the view of this single-document interface (SDI) application. All the controls are created in the view class OnCreate() function, which responds to the WM_CREATE Windows message. To set up this function, right-click CCommonView in ClassView and choose Add Windows Message Handler. Choose WM_CREATE from the list on the left and click Add and Edit. Add this line in place of the TODO comment:

Right-click CCommonView in ClassView again and this time choose Add Member Function. Enter void for the Function Type and enter CreateProgressBar() for the Function Declaration. Leave the access as Public. Click OK to add the function; then add the code in Listing 8.2.

CreateProgressBar() first creates the progress bar control by calling the control’s Create() function. This function’s four arguments are the control’s style flags, the control’s size (as a CRect object), a pointer to the control’s parent window, and the control’s ID. The resource ID, IDC_PROGRESSBAR, is added by hand. To add resource symbols to your own applications, choose View, Resource Symbols and click the New button. Type in a resource ID Name, such as IDC_PROGRESSBAR, and accept the default Value Visual Studio provides.

The style constants are the same constants that you use for creating any type of window (a control is nothing more than a special kind of window, after all). In this case, you need at least the following:

The WS_BORDER is a nice addition because it adds a dark border around the control, setting it off from the rest of the window.

To initialize the control, CCommonView::CreateProgressBar() calls SetRange(), SetStep(), and SetPos(). Because the range and the step rate are related, a control with a range of 1-10 and a step rate of 1 works almost identically to a control with a range of 1-100 and a step rate of 10.

When this sample application starts, the progress bar is already half filled with colored blocks. (This is purely for aesthetic reasons. Usually a progress bar begins its life empty.) It’s half full because CreateProgressBar() calls SetPos() with the value of 50, which is the midpoint of the control’s range.

Normally you update a progress bar as a long task moves toward completion. In this sample, you will fake it by using a timer. When the user clicks in the background of the view, start a timer that generates WM_TIMER messages periodically. Catch these messages and advance the progress bar. Here’s what to do:

This code enables users to turn the timer on or off with a click. The parameter of 500 in the SetTimer call is the number of milliseconds between WM_TIMER messages: This timer will send a message twice a second.

The StepIt() function increments the progress bar control’s value by the step rate, causing new blocks to be displayed in the control as the control’s value setting counts upward. When the control reaches its maximum, it automatically starts over.

Build Common and execute it to see the progress bar in action. Be sure to try stopping the timer as well as starting it.