Simple Gui in C

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Simple Gui in C
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Project Selecting
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(No Transcript)
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So Far

• Registering the window class
• Creating the window

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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

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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

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Message Queue

• There are no interrupts
• When messages are posted they are added to the
  message queue
• After handling them handle them they are removed

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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_NOMOVESWP_NOZORDER)
• Determines the window position and size.

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Painting

• When does painting occurs?
• After receiving WM_PAINT

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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)

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Painting functions

• LineTo(hdc, int x, int y)
• Line from current position to (x,y)
• MoveToEx(hdc, int x, int y, NULL)
• Move the cursor to (x,y)

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• 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_NOMOVESWP_NOZORDER)

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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

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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

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Adding Options
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For more Information

• A simple tutorial
• MSDN!!!

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Java - Graphics

• Working with Graphics object
• Graphics g
• DrawLine
• DrawRect
• SetColor
• .

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Applet

• An applet is a small, embeddable Java Program.
• Usually implementing a subclass of applet.

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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