画线

简单的画线程序。理解下对位图对象的使用。

/*----------------------------------------------------------------------
   	SKETCH.C -- 	Shadow Bitmap Demonstration
               						(c) Charles Petzold, 1998
  -------------------------------------------------------------------*/

#include <windows.h>
#include "resource.h"
LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;
int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    			PSTR szCmdLine, int iCmdShow)
{
     	static TCHAR 	szAppName [] = TEXT ("Sketch") ;
     	HWND         			hwnd ;
     	MSG          			msg ;
     	WNDCLASS     			wndclass ;
	

     	wndclass.style         			= CS_HREDRAW | CS_VREDRAW ;
     	wndclass.lpfnWndProc   			= WndProc ;
     	wndclass.cbClsExtra    			= 0 ;
     	wndclass.cbWndExtra    			= 0 ;
     	wndclass.hInstance     			= hInstance ;
     	wndclass.hIcon         			= LoadIcon (NULL, IDI_INFORMATION) ;
     	wndclass.hCursor       			= LoadCursor (NULL, IDC_ARROW) ;
     	wndclass.hbrBackground 		= (HBRUSH)GetStockObject(WHITE_BRUSH) ;
     	wndclass.lpszMenuName  		= NULL;
     	wndclass.lpszClassName 		= szAppName ;

   	if (!RegisterClass (&wndclass))
     	{
          		MessageBox (NULL, TEXT ("This program requires Windows NT!"),
                      							szAppName, MB_ICONERROR) ;
          		return 0 ;
     }

     	hwnd = CreateWindow (	szAppName, TEXT ("Sketch"),
                              WS_OVERLAPPEDWINDOW,
                          	  CW_USEDEFAULT, CW_USEDEFAULT,
                          	  CW_USEDEFAULT, CW_USEDEFAULT,
                          	  NULL, NULL, hInstance, NULL) ;
		if(hwnd == NULL){
		    MessageBox(NULL, TEXT("Not enough memory to create bitmap!"), szAppName, MB_ICONERROR);
			return 0;
		}

     	ShowWindow (hwnd, iCmdShow) ;
     	UpdateWindow (hwnd) ;
     	while (GetMessage (&msg, NULL, 0, 0))
     {
          			TranslateMessage (&msg) ;
          			DispatchMessage (&msg) ;
     }
   	return msg.wParam ;
}

void GetLargestDisplayMode(int *pcxBitmap, int *pcyBitmap)
{
	  DEVMODE  devmode;
	  int      iModeNum = 0;

	  * pcxBitmap = *pcyBitmap = 0;

	  ZeroMemory(&devmode, sizeof(DEVMODE));
	  devmode.dmSize = sizeof(DEVMODE);

	  while(EnumDisplaySettings(NULL, iModeNum++, &devmode))
	  {
		  *pcxBitmap = max(*pcxBitmap, (int)devmode.dmPelsWidth);
		  *pcyBitmap = max(*pcyBitmap, (int)devmode.dmPelsHeight);
	  }
}

LRESULT CALLBACK WndProc (	HWND hwnd, UINT message, WPARAM wParam,LPARAM lParam)
{       
	    static BOOL      fLeftButtonDown, fRightButtonDown;
		static HBITMAP   hBitmap;
		static HDC       hdcMem;
		static int       cxBitmap, cyBitmap, cxClient, cyClient, xMouse, yMouse;;
		HDC              hdc;
		PAINTSTRUCT      ps;

		switch(message)
		{
		case WM_CREATE:
			   GetLargestDisplayMode(&cxBitmap, &cyBitmap);

			   hdc = GetDC(hwnd);
			   hBitmap = CreateCompatibleBitmap(hdc, cxBitmap, cyBitmap);
			   hdcMem  = CreateCompatibleDC(hdc);
			   ReleaseDC(hwnd, hdc);

			   if(!hBitmap){
			       DeleteDC(hdcMem);
				   return -1;
			   }

			   SelectObject(hdcMem, hBitmap);
			   PatBlt(hdcMem, 0, 0, cxBitmap, cyBitmap, WHITENESS);
			   return 0;
		case WM_SIZE:
			   cxClient = LOWORD(lParam);
			   cyClient = LOWORD(lParam);
			   return 0;
		case WM_LBUTTONDOWN:
			    if(!fRightButtonDown) SetCapture(hwnd);

				xMouse = LOWORD(lParam);
				yMouse = HIWORD(lParam);
				fLeftButtonDown = TRUE;
				return 0;
		case  WM_LBUTTONUP:
			     if(fLeftButtonDown) SetCapture(NULL);
				 fLeftButtonDown = FALSE;
				 return 0;
		case WM_RBUTTONDOWN:
			     if(!fLeftButtonDown) SetCapture(hwnd);

				xMouse = LOWORD(lParam);
				yMouse = HIWORD(lParam);
				fRightButtonDown = TRUE;
				return 0;
		case WM_RBUTTONUP:
			     if(fRightButtonDown) SetCapture(NULL);

				 fRightButtonDown = FALSE;
				 return 0;
		case WM_MOUSEMOVE:
			     if(!fRightButtonDown && !fLeftButtonDown)
					 return 0;

				 hdc = GetDC(hwnd);
				 SelectObject(hdc, GetStockObject(fLeftButtonDown ? BLACK_PEN : WHITE_PEN));
				 SelectObject(hdcMem, GetStockObject(fLeftButtonDown ? BLACK_PEN : WHITE_PEN));

				 MoveToEx(hdc, xMouse, yMouse, NULL);
				 MoveToEx(hdcMem, xMouse, yMouse, NULL);

				 xMouse =(short) LOWORD(lParam);
				 yMouse =(short) HIWORD(lParam);

			     LineTo(hdc, xMouse, yMouse);
				 LineTo(hdcMem, xMouse, yMouse);

				 ReleaseDC(hwnd, hdc);
				 return 0;
		case WM_PAINT:
			     hdc = BeginPaint(hwnd, &ps);
				 BitBlt(hdc, 0, 0, cxClient, cyClient, hdcMem, 0, 0 ,SRCCOPY);

				 EndPaint(hwnd, &ps);
				 return 0;
		case WM_DESTROY:
			     DeleteDC(hdcMem);
				 DeleteObject(hBitmap);
				 PostQuitMessage(0);
				 return 0;

			  
		}
    	

     	return DefWindowProc (hwnd, message, wParam, lParam) ;
}