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Our Application with Clicks What do we need to display the locations of our clicks An application to act as main and instantiate the window Derive and instantiate a class from CWinApp Some mechanism of associating a mouse click message (or event) to a method (message or event handler)

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our application with clicks
Our Application with Clicks

What do we need to display the locations of our clicks

  • An application to act as main and instantiate the window
    • Derive and instantiate a class from CWinApp
  • Some mechanism of associating a mouse click message (or event) to a method (message or event handler)
    • We’ll need another Message Map to do this
  • A way to display the contents of our window
    • Some way to represent get the coordinates of our click
    • Clean way to convert these numerical points to a character array
capturing mouse clicks
Capturing Mouse Clicks
  • System has built-in routines to capture mouse clicks
    • OnLButtonDown, OnLButtonUp
    • OnRButtonDown, OnRButtonUp
  • All four routines take two parameters
    • UINT flags, a 32-bit unsigned integer
    • CPoint point, a class for points, x and y coordinates are available (can retrieve), as well as other operations
program captures mouse clicks
#include <afxwin.h>

#include <string>

using namespace std;

class CMouseWin : publicCFrameWnd{

public:CMouseWin();afx_msg void OnLButtonDown(UINT, CPoint);afx_msg void OnRButtonDown(UINT, CPoint);afx_msg void OnLButtonUp(UINT, CPoint);afx_msg void OnRButtonUp(UINT, CPoint);

private:void showUp(CPoint);void showDown(CPoint);DECLARE_MESSAGE_MAP( )


Our class will provide new methods for processing the various mouse click events

Utilizes two private methods to process these mouse clicks (showUp and showDown)

Program captures mouse clicks
program body part one
#include <strstrea.h>

#include "example.h"

CMouseWin::CMouseWin() {

Create(NULL, "Mouse Click Example", WS_OVERLAPPEDWINDOW,

CRect(100,100,500,500)); }

afx_msg void CMouseWin::OnLButtonDown(UINT uFlags, CPoint point){ showDown(point); }

afx_msg void CMouseWin::OnLButtonUp(UINT uFlags, CPoint point) { showUp(point); }

afx_msg void CMouseWin::OnRButtonDown(UINT uFlags, CPoint point) { showDown(point); }

afx_msg void CMouseWin::OnRButtonUp(UINT uFlags, CPoint point) { showUp(point); }

One new header file (will use it shortly)

Constructor creates a standard window

Four methods defined to capture each of the four mouse actions

Two methods call the showDown method (press mouse button)

Two methods call the showUp method (release mouse button)

Program Body (part one)
program body part two
void CMouseWin::showDown(CPoint point) {

CClientDC dc(this);

ostrstream s;

s << "(" << point.x << ",“ << point.y << ")";

dc.TextOut(50,50,s.str(), s.pcount());


void CMouseWin::showUp(CPoint point) {

CClientDC dc(this);

char carText[32];

ostrstream s(carText, sizeof(carText));

s << "(" << point.x << ",“ << point.y << ")";

dc.TextOut(200,200,carText, s.pcount());


New concept here (writing to a string)

Already seen writing to files and stdout

Can also write to an array of chars


Declare array

Declare output stream

Write to it (s.pcount has count of chars written)

Take this array (with the output that was written to it) and display it in the window

Program Body (part two)
program body part three

( CMouseWin,CFrameWnd)






class CMouseApp : publicCWinApp{


BOOL InitInstance( ) {

m_pMainWnd= new CMouseWin;

m_pMainWnd->ShowWindow (m_nCmdShow);


return TRUE; }

} mouseApp;

Message map section defines four events that this program is watching out for (all related to mouse buttons). All four are built into the system, you don’t need to define further

Standard clause at the end of the program to get things started (register mouseApp with WinMain and have it invoked when the program starts)

Program Body (part three)
class exercises
Class Exercises
  • Modify the code from the previous “catching mouse clicks example” so that:
    • The right mouse button down and up locations are printed at the top of the window (in the left and right corners)
    • The left mouse button down and up locations are printed at the bottom of the window (in the left and right corners)
    • Files
      • MouseWin.h
      • MouseWin.cpp
drawing on the window
Drawing on the window
  • Similar to writing text on the window

CClientDC dc(this); // get window context

dc.TextOut( … ) // write out some text

  • Routines exist to do almost anything
  • We will focus on routines to:
    • Move to a given location
    • Draw a line from where you are to another location
    • Create a filled rectangle of some color
sample drawing program
Sample drawing program
  • Want to be able to write text on the screen
    • Already seen this (Menu example)
  • New capabilities
    • Want to be able to draw lines on the screen
    • Want to be able to draw shapes on the screen
  • Example
    • Extremely “simplistic” version of tic-tac-toe
    • Menu with two options (“new” and “quit”)
    • Draw a simple board, click to indicate moves

Use red and blue blocks instead of X’s and O’s

header file for program
#include <afxwin.h>

class CTTTWin : public CFrameWnd {

public:CTTTWin();~CTTTWin();afx_msg void OnExit();afx_msg void OnNew();afx_msg void OnLButtonDown (UINT uFlags, CPoint point);

private:void DrawBoard();int m_iToggle;DECLARE_MESSAGE_MAP( )


Standard class header

Handle two “menu events” (new and quit)

Handle the left mouse down event (processing occurs as soon as you press the mouse button)

Private routine DrawBoard is used to draw an image on the window

Header file for program
program body part one11
#include “TTTWin.h"

#include "menus.h“

CTTTWin::CTTTWin() {


CRect(100,100,410,450), NULL, "MyMenus");

m_iToggle = 0;


CTTTWin::~CTTTWin() { }

afx_msg void CTTTWin::OnNew()

{ m_iToggle = 0; DrawBoard(); }

afx_msg void CTTTWin::OnExit()

{ SendMessage(WM_CLOSE); }

Constructor builds basic window

Our board is 300x300

Need a little extra height as window header stuff counts in overall size

Destructor does nothing

When “new” menu item is selected, draw a new board

Quit program when “quit” option is selected

Program body (part one)
program body part two12
void CTTTWin::DrawBoard() {

CClientDC dc(this);

CBrush *pBrush = new CBrush();


dc.FillRect(CRect(0,0,300,300), pBrush);

CPen *pPen = new CPen;

pPen->CreatePen(PS_SOLID, 1, RGB(0,0,0) );

dc.MoveTo(0,100); dc.LineTo(300,100);

dc.MoveTo(0,200); dc.LineTo(300,200);

dc.MoveTo(100,0); dc.LineTo(100,300);

dc.MoveTo(200,0); dc. LineTo(200,300);


Use CBrush and FillRect to paint full device (window) white

Use Cpen, MoveTo, and LineTo to draw lines for TicTacToe Board

Program body (part two)
program body part three13
afx_msg void CTTTWin::OnLButtonDown (UINT uFlags, CPoint point) {

CClientDC dc(this);

CBrush *pBrush = new CBrush();

if (m_iToggle) {


dc.FillRect(CRect(point.x-20,point.y-20, point.x+20,point.y+20), pBrush);

m_iToggle = 0; }

else {


dc.FillRect(CRect(point.x-20, point.y-20, point.x+20,point.y+20), pBrush);

m_iToggle = 1;



To process a mouse click, we draw a rectangle (using FillRect) around where you clicked and then change colors (assuming the next move is from the other player)

No checking of location of click is done

Program body (part three)
program body part four


class CTTTApp : public CWinApp {


BOOL InitInstance() {m_pMainWnd = new CTTTWin;m_pMainWnd->ShowWindow (m_nCmdShow);m_pMainWnd->UpdateWindow();return TRUE;


} tttApp;

Standard message map, we want to handle two unique menu items, don’t need to worry about mouse clicks (built into system)

Standard clause to invoke/control execution of program (via WinApp)

Program body (part four)
extra menu files needed

#include <afxres.h>

#include "menus.h"

MyMenus MENU{

POPUP "Tic-Tac-Toe" {






#define IDM_EXIT 5000

#define IDM_NEW 5001

Extra “menu” files needed
events messages
Events (messages)
  • Each message has a unique id associated with it
    • Windows-defined
      • ID’s 0 – 1023
    • You-defined
      • Can name between 1024 –65535
  • Naming Convention:
    • ID’s
      • WM_MESSAGE: Windows Message
      • IDM_MESSAGE: Menu Id
    • Handlers (methods)
      • OnMessage
event message handlers
Event/Message Handlers
  • Each unique message ID needs to be associated with message handler (method)
    • MFC-defined
      • Has already been associated
      • Use pre-defined macro ON_WM_MESSAGE()in message to signify it is to be handled in the class specified in the BEGIN_MESSAGE_MAP params
    • You-defined
      • You must make the association
      • Use macro ON_COMMAND(ID, OnMessage)
macros message map
Macros / Message Map
  • The macros we use have already been defined. Before compilation time, there is a text replacement where we use the macro identifier.
  • We have been using the Message Map macros(where we associate a message ID to its handler)

BEGIN_MESSAGE_MAP(owner-class name, base-class name)


ON_WM_MESSAGE() // for pre-defined

ON_COMMAND(ID, OnMessage) //for you-defined


  • For more than you want to know about message maps
    • http://msdn.microsoft.com/library/default.asp?URL=/library/devprods/vs6/visualc/vcmfc/_mfcnotes_tn006.htm
message boxes
Message Boxes
  • Often want to pop up a little window to let the user know something
    • Information
    • Question
    • Notification
  • MessageBox class simplifies this process
    • MessageBox has a title
    • MessageBox displays information
    • MessageBox might have
      • Icons and/or selections for the user to pick
messagebox example
Four basic types of message boxes exist

Our example will generate one of four message boxes depending on which mouse button you click and where you clicked it

Will see a more complete description of message boxes shortly

#include <afxwin.h>

class CMessageWin : publicCFrameWnd {




afx_msg void OnLButtonDown

(UINT uFlags, CPoint point);

afx_msg void OnRButtonDown

(UINT uFlags, CPoint point);




MessageBox example
body of the program 1
#include <afxwin.h>

#include “MessageWin.h"

CMessageWin::CMessageWin() {

Create(NULL, "MessageBox Example",WS_OVERLAPPEDWINDOW,CRect(100,100,500,500));


CMessageWin::~CMessageWin() { }

Standard include files



Body of the program (1)
body of the program 2
Body of the program (2)

afx_msg void CMessageWin::OnLButtonDown(UINT uFlags, CPoint point) { // handle left button click

if (point.x < 200)MessageBox("x coordinate is small", "Stop Message Box", MB_ICONSTOP);

elseMessageBox("x coordinate is large", "Question Message Box", MB_ICONQUESTION);


afx_msg void CMessageWin::OnRButtonDown(UINT uFlags, CPoint point) { // handle right button click

if (point.y < 200) MessageBox("y coordinate is small", "Exclamation Message Box", MB_ICONEXCLAMATION);

elseMessageBox("y coordinate is large", "Info Message Box", MB_ICONINFORMATION);


body of the program 3
BEGIN_MESSAGE_MAP(CMesssageWin, CFrameWnd)




class CMessageApp : public CWinApp



BOOL InitInstance() {m_pMainWnd = new CMessageWin;m_pMainWnd->ShowWindow(m_nCmdShow);m_pMainWnd->UpdateWindow();return TRUE;


} MessageApp;

Our message map section indicates we are interested in capturing two types of events

Left button down

Right button down

Standard main portion

Body of the program (3)