Simple Gui in C++

Project Selecting

So Far

• Registering the window class

• Creating the window

So Far

The major function/Handling Messages

• WndProc• Return value: LRESULT CALLBACK• Parameters: HWND hWnd

UINT message WPARAM wParam LPARAM lParam):• The function handles all events (message):

– WM_CREATE– WM_PAINT– WM_LBUTTONUP

Handling Messages(Cont)

• Historically wParam 16 bit lParam 32 bit; Today both 32 bit

• Each message use those parameters differently

• For example– WM_LBUTTON - lParam stores coordinates

• LOWORD, HIWORD – extract two words

Message Queue

• There are no interrupts

• When messages are posted they are added to the message queue

• After handling them they are removed

Working with Rectangles

• GetWindowRect(m_hWnd,&rt1) – return the window rectangle in screen

coordinates

• GetClientRect(m_hWnd,&rt2) – return window rectangle in "itself" coordinates

• SetWindowPos(m_hWnd,NULL,0,0,x,y ,SWP_NOMOVE|SWP_NOZORDER);– Determines the window position and size.

Painting

• When does painting occur?

• After receiving WM_PAINT

How to Paint

• First get an handle to the screen

hdc = BeginPaint(hWnd, &ps);

• Using hdc in each “painting” function.

• Do not forget– EndPaint(hWnd, &ps);

Painting functions

• LineTo(hdc, int x, int y);– Line from current position to (x,y)

• MoveToEx(hdc, int x, int y, NULL)– Move the position to (x,y)

case WM_PAINT:hdc = BeginPaint(hWnd, &ps);// TODO: Add any drawing code here...RECT rt,rt1;GetClientRect(hWnd, &rt);GetWindowRect(hWnd, &rt1);int x, y;y = (rt1.bottom - rt1.top) - rt.bottom;x = (rt1.right - rt1.left) - rt.right;

//DrawText(hdc, szHello, strlen(szHello), &rt, DT_CENTER);MoveToEx(hdc,0,0, NULL);LineTo(hdc, 100,0);LineTo(hdc, 100,100);LineTo(hdc, 0,100);LineTo(hdc,0,0);

SetWindowPos(hWnd,NULL,0,0,100 + x + 1, 100 + y + 1,SWP_NOMOVE|SWP_NOZORDER);

EndPaint(hWnd, &ps);

Painting (Cont)

• CreatePen( int nPenStyle, int nWidth, COLORREF crColor )– Can paint in different styles and colors

• SelectObject(hdc, HPEN pen) – The next object will be painted by pen

• Ellipse(x,y,x1,y1)– The coordinates of the bounding rectangle

Alternative Ways• CPen* SelectObject( hdc, CPen* pPen );

• CBrush* SelectObject( hdc, CBrush* pBrush );

• CBitmap* SelectObject(hdc, CBitmap* pBitmap );

• Etc…

Working with Bitmap(See Roy Bubis and Keren Michaeli

Proj)• Insert Bitmaps to Resources• LoadImage• CreateCompatibleDC ( hdc ); -

– Working on another hdc to avoid flickering

• SelectObject(memdc, bmp); • TransparentBlt(hdc,x,y, dx, dy,

memdc,0,0,width, height, RGB(255,0,0));• //passing the content of medc to hdc•

Forcing RePaint

• InvalidateRect(m_hWnd,&rect,TRUE); – signal the OS that this window is invalid and

need to be repaint. – The OS send all the invalid windows the

WM_PAINT message

How does it look?

Adding Options

For more Information

• A simple tutorial

• MSDN!!!

Java - Graphics

• Working with Graphics object

• Graphics g– DrawLine– DrawRect– SetColor– ….

Applet

• An applet is a small, embeddable Java Program.

• “Usually” implementing a subclass of applet.

Handling events

• The events that we want to handle should be define in our subclass

• boolean mouseDown(Event e, int x, int y)

• Boolean mouseDrag(Event e, int x, int y)

• boolean keyDown(Event e, int x, int y)

• Etc…