L_DoubleBufferEnd

#include "l_bitmap.h"

L_INT EXT_FUNCTION L_DoubleBufferEnd(hDoubleBufferHandle, hDC)

L_HANDLE hDoubleBufferHandle;	/* double buffering handle */
HDC hDC;	/* handle to the target device context */

Displays the double buffered paint operations. This function is available in the Document/Medical Toolkits.

Parameter	Description
hDoubleBufferHandle	Handle that identifies the double buffering process.
hDC	Handle to the original target device context.

Returns

SUCCESS	The function was successful.
< 1	An error occurred. Refer to Return Codes.

Comments

Use L_DoubleBufferEnd when ready to paint all that has been double-buffered to the target hDC. All double buffered paint operations should be wrapped in L_DoubleBufferBegin and L_DoubleBufferEnd 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 L_DoubleBufferBegin.

Note that you must create a double buffer handle with L_DoubleBufferCreateHandle 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

Windows 95 / 98 / Me, Windows 2000 / XP.

See Also

Functions:	L_DoubleBufferEnable, L_DoubleBufferCreateHandle, L_DoubleBufferDestroyHandle, L_DoubleBufferBegin
Topics:	Raster Image Functions: Displaying Images
	Minimizing Flicker With Double Buffering

Example

To see how double buffering can be used in an application, see the source code for the API annotation demo.

// 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_VOID SampleDoubleBuffer(HWND hWnd, L_TCHAR *pszFile, L_BOOL bDoubleBuffer)
{
   HBRUSH hBrush;
   BITMAPHANDLE Bitmap;
   L_HANDLE hDoubleBufferHandle;
   L_INT cx, cy;
   HDC hDC, hMemDC;
   RECT rcClient;
   RECT rcBitmap;
   RECT rcBall;
   L_INT dx, dy;
   L_INT i;
   L_INT nRet;

   nRet = L_LoadBitmap(pszFile, &Bitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGRORGRAY, NULL, NULL);
   if (nRet != SUCCESS)
   {
      MessageBox(hWnd, TEXT("Failed to load image"), TEXT("Error"), MB_OK);
      return;
   }

   hBrush = CreateSolidBrush( RGB(100,100,100));
   L_DoubleBufferCreateHandle(&hDoubleBufferHandle);

   L_DoubleBufferEnable(hDoubleBufferHandle, 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 = BITMAPWIDTH(&Bitmap);
   rcBitmap.bottom = BITMAPWIDTH(&Bitmap);

   SetRect(&rcBall, 0, 0, BALL_RADIUS, BALL_RADIUS);
   dx = dy = 1;
   for (i=0; i<2000; i++)
   {
      // Double buffer painting the image and the moving ball
      hMemDC = L_DoubleBufferBegin(hDoubleBufferHandle, hDC, cx, cy);
      FillRect(hMemDC, &rcClient, hBrush);
      L_PaintDC(hMemDC, &Bitmap, NULL, NULL, &rcBitmap, NULL, SRCCOPY);
      Ellipse(hMemDC, rcBall.left, rcBall.top, rcBall.right, rcBall.bottom);
      L_DoubleBufferEnd(hDoubleBufferHandle, hDC);

      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
   L_FreeBitmap(&Bitmap);
   L_DoubleBufferDestroyHandle(hDoubleBufferHandle);
   DeleteObject(hBrush);
}