Mouse Messages

Responding to Mouse Messages

Since Windows is, to a great extent, a mouse-based operating system, all Windows NT programs should respond to mouse input. Because the mouse is so important, there are several different types of mouse messages. The ones discussed in this lecture are:

WM-LBUTTONDBLCK WM_LBUTTONUP WM_LBUTTONDOWN WM_RBUTTONDBLCK WM_RBUTTONUP WM_RBUTTONDOWN
While most computers use a two-button mouse, Windows NT is capable of handling a mouse with up to three buttons. These buttons are called the left, middle, and right. For the rest of this chapter we will only be concerned with the left and right buttons.

Let s begin with the two most common mouse messages, WM_LBUTTONDOWN and WM_RBUTTONDOWN. They are generated when the left button and right button are pressed, respectively.
When either a WM_LBUTTONDOWN or a WM_RBUTTONDOWN message is received, the mouse s current X, Y location is specified in LOWORD(LParam) and HIWORD(lParam), respectively. The value of wParam contains various pieces of status information, which are described in the next section.
The following program responds to mouse messages. Each time you press a mouse button when the program s window contains the mouse cursor, a message will be displayed at the current location of the mouse pointer.