Visual C++ and MFC Programming 2nd Edition

Visual C++ and MFC Fundamentals Chapter 5: The Document/View Architecture

Imagine the user has located a position or an item on a document and presses one of the

mouse buttons. While the button is pressed and is down, a button-down message is sent,

depending on the button that was pressed.

If the left mouse button was pressed, an ON_WM_LBUTTONDOWN message is sent.

The syntax of this message is:

afx_msg void OnLButtonDown(UINT nFlags, CPoint point);

If the right mouse button was pressed, an ON_WM_RBUTTONDOWN message is sent.

Its syntax is:

afx_msg void OnRButtonDown(UINT nFlags, CPoint point);

The first argument, nFlags, specifies what button is down or what keyboard key and what

mouse button are down. It is a constant integer that can have one of the following values:

Value Description

MK_CONTROL A Ctrl key is held down

MK_LBUTTON The left mouse button is down

MK_MBUTTON The middle mouse button is down

MK_RBUTTON The right mouse button is down

MK_SHIFT A Shift key is held down

The point argument specifies the measure from the left and the top borders of the window

to the mouse pointer.

Practical Learning: Sending a Mouse Down Message

1. To experiment with the mouse down effect, change the program as follows:

#include <afxwin.h>

class CMainFrame : public CFrameWnd

{

public:

CMainFrame ();

protected:

afx_msg int OnCreate(LPCREATESTRUCT lpCreateStruct);

afx_msg void OnKeyDown(UINT nChar, UINT nRepCnt, UINT nFlags);

afx_msg void OnLButtonDown(UINT nFlags, CPoint point);

DECLARE_MESSAGE_MAP()

};

CMainFrame::CMainFrame()

{

// Create the window's frame

Create(NULL, "Windows Application", WS_OVERLAPPEDWINDOW,

CRect(120, 100, 700, 480), NULL);

}

class CExerciseApp: public CWinApp

{

public:

BOOL InitInstance();