C / C++ / MFC

Member 4253145 wrote:

Can you please explain,

i) why this OnSelchanged() method is getting called multiple times whenever myCtrl.SetItemState( itemID, LVIS_SELECTED, LVIS_SELECTED );line of code gets executed.

BOOL DrawTransparentBitmap(HDC hdc, 
		   HBITMAP hBitmap, 
		   __int32 xStart,
		   __int32 yStart, 
		   COLORREF cTransparentColor)
{

	BITMAP     bm;
	COLORREF   cColor;
	HBITMAP    bmAndBack, bmAndObject, bmAndMem, bmSave;			// lots of storage
	HBITMAP    bmBackOld, bmObjectOld, bmMemOld, bmSaveOld, bmTempOld;
	HDC        hdcMem, hdcBack, hdcObject, hdcTemp, hdcSave;		// lots of dc's
	POINT      ptSize;
	
	int iCaps = ::GetDeviceCaps(hdc, RASTERCAPS);
	if ((iCaps & RC_BITBLT) != RC_BITBLT)
	{
		return FALSE;
	}
	
	if ((iCaps & RC_BITMAP64) != RC_BITMAP64)
	{
		return FALSE;
	}
	
	hdcTemp = CreateCompatibleDC(hdc);
	
	if (hdcTemp==NULL) 
        {
		return FALSE;
	}
	
	bmTempOld = (HBITMAP)SelectObject(hdcTemp, hBitmap);   // Select the bitmap
	
	if (GetObject(hBitmap, sizeof(BITMAP), (LPSTR)&bm) != sizeof(BITMAP))
   {
                DeleteDC(hdcTemp);
		return FALSE;
   }

	ptSize.x = bm.bmWidth;            // Get width of bitmap
	ptSize.y = bm.bmHeight;           // Get height of bitmap
	DPtoLP(hdcTemp, &ptSize, 1);      // Convert from device
	// to logical points
	
	// Create some DCs to hold temporary data.
	hdcBack   = CreateCompatibleDC(hdc);
	hdcObject = CreateCompatibleDC(hdc);
	hdcMem    = CreateCompatibleDC(hdc);
	hdcSave   = CreateCompatibleDC(hdc);
	
	// Create a bitmap for each DC. DCs are required for a number of
	// GDI functions.
	
	// Monochrome DC
	bmAndBack   = CreateBitmap(ptSize.x, ptSize.y, 1, 1, NULL);
	
	// Monochrome DC
	bmAndObject = CreateBitmap(ptSize.x, ptSize.y, 1, 1, NULL);
	
	bmAndMem    = CreateCompatibleBitmap(hdc, ptSize.x, ptSize.y);
	bmSave      = CreateCompatibleBitmap(hdc, ptSize.x, ptSize.y);
	
	// Each DC must select a bitmap object to store pixel data.
	// (HBITMAP) Casts added by CDL, 3/26/96
	bmBackOld   = (HBITMAP)SelectObject(hdcBack, bmAndBack);
	bmObjectOld = (HBITMAP)SelectObject(hdcObject, bmAndObject);
	bmMemOld    = (HBITMAP)SelectObject(hdcMem, bmAndMem);
	bmSaveOld   = (HBITMAP)SelectObject(hdcSave, bmSave);
	
	// Set proper mapping mode.
	SetMapMode(hdcTemp, GetMapMode(hdc));
	
	// Save the bitmap sent here, because it will be overwritten.
	BitBlt(hdcSave, 0, 0, ptSize.x, ptSize.y, hdcTemp, 0, 0, SRCCOPY);
	
	// Set the background color of the source DC to the color.
	// contained in the parts of the bitmap that should be transparent
	cColor = SetBkColor(hdcTemp, cTransparentColor);
	
	// Create the object mask for the bitmap by performing a BitBlt
	// from the source bitmap to a monochrome bitmap.
	BitBlt(hdcObject, 0, 0, ptSize.x, ptSize.y, hdcTemp, 0, 0,
		SRCCOPY);
	
	// Set the background color of the source DC back to the original
	// color.
	SetBkColor(hdcTemp, cColor);
	
	// Create the inverse of the object mask.
	BitBlt(hdcBack, 0, 0, ptSize.x, ptSize.y, hdcObject, 0, 0, NOTSRCCOPY);
	
	// Copy the background of the main DC to the destination.
	BitBlt(hdcMem, 0, 0, ptSize.x, ptSize.y, hdc, xStart, yStart, SRCCOPY);
	
	// Mask out the places where the bitmap will be placed.
	BitBlt(hdcMem, 0, 0, ptSize.x, ptSize.y, hdcObject, 0, 0, SRCAND);
	
	// Mask out the transparent colored pixels on the bitmap.
	BitBlt(hdcTemp, 0, 0, ptSize.x, ptSize.y, hdcBack, 0, 0, SRCAND);
	
	// XOR the bitmap with the background on the destination DC.
	BitBlt(hdcMem, 0, 0, ptSize.x, ptSize.y, hdcTemp, 0, 0, SRCPAINT);
	
	// Copy the destination to the screen.
	BitBlt(hdc, xStart, yStart, ptSize.x, ptSize.y, hdcMem, 0, 0, SRCCOPY);
	
	// Place the original bitmap back into the bitmap sent here.
	BitBlt(hdcTemp, 0, 0, ptSize.x, ptSize.y, hdcSave, 0, 0, SRCCOPY);
	
	// Delete the memory bitmaps.
	DeleteObject(SelectObject(hdcBack, bmBackOld));
	DeleteObject(SelectObject(hdcObject, bmObjectOld));
	DeleteObject(SelectObject(hdcMem, bmMemOld));
	DeleteObject(SelectObject(hdcSave, bmSaveOld));
        SelectObject(hdcTemp, bmTempOld);

	// Delete the memory DCs.
	DeleteDC(hdcMem);
	DeleteDC(hdcBack);
	DeleteDC(hdcObject);
	DeleteDC(hdcSave);
	DeleteDC(hdcTemp);

    return TRUE;
}