如何编码减少闪烁？需要你的代码帮助.win32 VC++闪烁

Question

我试图用鼠标movemont将位图缩放到鼠标光标位置.但是有闪烁的问题.

我读过关于双缓冲以减少闪烁,但我不知道如何...这会导致极度闪烁.我已经阅读了关于双缓冲以减少闪烁,但我不确定如何在此示例中实现它.你能帮忙吗？谢谢

这是下面的代码.谢谢你的帮助!

// screen blinks.trying to use double buffer so solve this problem.
#include <windows.h>
HDC bufferDC = NULL;
HDC           hdc=GetWindowDC(NULL) ;
HDC hammerDC = NULL; 
HBITMAP hammer1BMP = NULL;
HBITMAP bufferBMP = NULL;
POINT cursorpoint;

LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
{
     static TCHAR szAppName[] = TEXT ("DigClock") ;
     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_APPLICATION);
     wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;
     wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;
     wndclass.lpszMenuName  = NULL ;
     wndclass.lpszClassName = szAppName ;

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

     hwnd = CreateWindow (szAppName, TEXT ("Digital Clock"),
                          WS_OVERLAPPEDWINDOW,
                          CW_USEDEFAULT, CW_USEDEFAULT,
                          CW_USEDEFAULT, CW_USEDEFAULT,
                          NULL, NULL, hInstance, NULL) ;

     ShowWindow (hwnd, iCmdShow) ;
     UpdateWindow (hwnd) ;


     bufferDC=CreateCompatibleDC(hdc);
     hammerDC=CreateCompatibleDC(hdc);
     hammer1BMP=(HBITMAP)LoadImage(NULL,"star.bmp",IMAGE_BITMAP,160,160,LR_LOADFROMFILE);
     SelectObject(hammerDC,hammer1BMP);

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

LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
     static BOOL   f24Hour, fSuppress ;
     static HBRUSH hBrushRed ;
     static int    cxClient, cyClient ;
     HDC           hdc ;
     PAINTSTRUCT   ps ;
     TCHAR         szBuffer [2] ;

     switch (message)
     {
     case WM_CREATE:
          hBrushRed = CreateSolidBrush (RGB (255, 0, 0)) ;
          SetTimer (hwnd, ID_TIMER, 1000/24,NULL) ;//1000

                                                  // fall through

     case WM_SETTINGCHANGE:

          InvalidateRect (hwnd, NULL, TRUE) ;
          return 0 ;

     case WM_SIZE:
          cxClient = LOWORD (lParam) ;
          cyClient = HIWORD (lParam) ;
          return 0 ;

     case WM_TIMER:
          InvalidateRect (hwnd, NULL, TRUE) ;
          return 0 ;

     case WM_PAINT:
          hdc = BeginPaint (hwnd, &ps) ;
          bufferBMP=CreateCompatibleBitmap(hdc,cxClient,cyClient);
          SelectObject(bufferDC,bufferBMP);
          // SelectObject(bufferDC,hammer1BMP); 
          GetCursorPos(&cursorpoint);
          BitBlt(bufferDC,0,0,cxClient,cyClient,hammerDC,0,0,SRCCOPY);
          BitBlt(hdc,cursorpoint.x,cursorpoint.y,cxClient,cyClient,bufferDC,0,0,SRCCOPY);


          EndPaint (hwnd, &ps) ;
          return 0 ;
     case WM_LBUTTONDOWN:
         // GetCursorPos(&cursorpoint);
          //BitBlt(hdc,cursorpoint.x,cursorpoint.y,cxClient,cyClient,hammerDC,0,0,SRCCOPY);
          return 0;
     case WM_DESTROY:
          KillTimer (hwnd, ID_TIMER) ;
          DeleteDC(hammerDC);
          DeleteObject (hBrushRed) ;
          PostQuitMessage (0) ;
          return 0 ;
     }
     return DefWindowProc (hwnd, message, wParam, lParam) ;
}

Answer 1

在这种情况下,看起来你真的不需要双缓冲 - 事实上,它可能根本不会帮助你.

闪烁的主要原因是擦除背景,然后立即将其覆盖.由于您显然是在WM_PAINT中绘制窗口的整个客户区域,因此只需为WM_ERASEBKGND添加一个处理程序,该处理程序除了返回TRUE以表示背景已被删除外什么都不做.

编辑(回复评论):

更完整,几乎每次用一种颜色绘制区域时都会产生闪烁效果,然后用另一种颜色快速重新绘制.双重缓冲有助于当/如果您的前景具有多个不同颜色的重叠元素.您将(至少)覆盖区域绘制到后台缓冲区中,然后只有当您拥有正确的颜色时,才将它们绘制到屏幕上.在这种情况下,原始代码会进行双重缓冲,但它仍然会绘制背景,然后是前景,并且仍然会闪烁.

另一个答案提到将false作为第二个参数传递给InvalidateRect.这将有很大帮助,因为它不会重新绘制背景以响应InvalidateRect.只会绘制前景,所以它将无闪烁.不幸的是,当窗口的矩形(至少部分)由于任何其他原因而无效时,你仍然会闪烁,因为它仍然会绘制背景,然后是前景.