LDoubleBuffer::End

#include "ltwrappr.h"

virtual L_INT LDoubleBuffer::End(hDC)

HDC hDC;

handle to the target device context

Displays the double buffered paint operations.

Parameter

Description

hDC

Handle to the original target device context

Returns

SUCCESS

The function was successful.

< 1

An error occurred. Refer to Return Codes.

Comments

Use LDoubleBuffer::End when ready to paint all that has been double-buffered to the target hDC. All double buffered paint operations should be wrapped in LDoubleBuffer::Begin and LDoubleBuffer::End calls.

The hDC argument is the device context that you want to double buffer, which in this case should be the same as the hDC argument that was passed to LDoubleBuffer::Begin.

Note that you must create a double buffer handle with LDoubleBuffer::CreateHandle before calling this function.

For more information, see the topic Minimizing Flicker with Double Buffering.

Required DLLs and Libraries

LTDIS

For a listing of the exact DLLs and Libraries needed, based on the toolkit version, refer to Files To Be Included With Your Application.

Platforms

Win32, x64.

See Also

Functions:

Class Members

Topics:

Raster Image Functions: Displaying Images

 

Minimizing Flicker with Double Buffering

Example

This sample illustrates double buffering by bouncing a ball around a window that contains an image For simplicity, we assume both the window the hDC are 24 bit Run the example twice --

  • once with bDoubleBuffer set to FALSE
  • once with bDoubleBuffer set to TRUE to see the difference hWnd -- window to paint image and bounce ball pszFile -- file name of image to load bDoubleBuffer - flag saying whether or not to double buffer the paints#define BALL_RADIUS 30
    L_INT LDoubleBuffer__EndExample(HWND hWnd, L_TCHAR *pszFile, L_BOOL bDoubleBuffer)  
    { 
       HBRUSH hBrush;  
       LBitmap Bitmap;  
       LDoubleBuffer LDoubleBufferObj;  
       L_INT cx, cy;  
       HDC hDC, hMemDC;  
       RECT rcClient;  
       RECT rcBitmap;  
       RECT rcBall;  
       L_INT dx, dy;  
       L_INT i;  
       L_INT nRet;  
     
       nRet = Bitmap.Load(pszFile, 0, ORDER_BGRORGRAY, NULL, NULL);  
       if (nRet != SUCCESS)  
       { 
          MessageBox(hWnd, TEXT("Failed to load image"), TEXT("Error"), MB_OK);  
          return nRet;  
       } 
     
       hBrush = CreateSolidBrush( RGB(100,100,100));  
       LDoubleBufferObj.CreateHandle(); 
     
       LDoubleBufferObj.EnableDoubleBuffer(bDoubleBuffer);  
     
       GetClientRect(hWnd, &rcClient);  
       cx = rcClient.right  - rcClient.left;  
       cy = rcClient.bottom - rcClient.top;  
       hDC = GetDC(hWnd);  
     
       rcBitmap.left = 0;  
       rcBitmap.top = 0;  
       rcBitmap.right = Bitmap.GetHeight(); 
       rcBitmap.bottom = Bitmap.GetWidth(); 
     
       SetRect(&rcBall, 0, 0, 75, 75);  
       dx = dy = 1;  
       for (i=0; i<2000; i++) 
       { 
          // Double buffer painting the image and the moving ball 
          hMemDC = LDoubleBufferObj.Begin(hDC, cx, cy);  
          FillRect(hMemDC, &rcClient, hBrush);  
          nRet = Bitmap.SetDstRect(&rcBitmap);  
          if(nRet != SUCCESS) 
             return nRet; 
     
          LPaint MyPaint(&Bitmap, hMemDC);  
     
          nRet = MyPaint.PaintDC(); 
          if(nRet != SUCCESS) 
             return nRet; 
     
          Ellipse(hMemDC, rcBall.left, rcBall.top, rcBall.right, rcBall.bottom);  
     
          nRet = LDoubleBufferObj.End(hDC);  
          if(nRet != SUCCESS) 
             return nRet; 
     
          if ((rcBall.bottom) > rcClient.bottom)  
             dy = -1;  
          if (rcBall.top < 0)  
             dy = 1;  
          if (rcBall.left < 0)  
             dx = 1;  
          if ((rcBall.right) > rcClient.right)  
             dx = -1;  
          OffsetRect(&rcBall, dx, dy);  
       } 
     
       // Cleanup 
       nRet = Bitmap.Free(); 
       if(nRet != SUCCESS) 
          return nRet; 
     
       nRet = LDoubleBufferObj.DestroyHandle(); 
       if(nRet != SUCCESS) 
          return nRet; 
     
       DeleteObject(hBrush);  
     
       return SUCCESS; 
    } 
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