Creating Drag Image for a CTreeCtrl without images

CodeGuru content and product recommendations are editorially independent. We may make money when you click on links to our partners. Learn More.

The method CreateDragImage is used during drag’n drop to create a
drag image. The problem is that it only works for a CTreeCtrl with
images. The following method, CreateDragImageEx, checks whether the
CTreeCtrl has a valid normal CImageList. If so, it just calls the
standard CreateDragImage method and returns.

If, on the other hand, no valid CImageList is found, a bitmap is created
based on the size of item rect, and the item text is drawn into it.
Then a CImageList is created and the bitmap is added to it.

CImageList* CTreeCtrlEx::CreateDragImageEx(HTREEITEM hItem)
{
	if(GetImageList(TVSIL_NORMAL) != NULL)
		return CreateDragImage(hItem);

	CRect rect;
	GetItemRect(hItem, rect, TRUE);
	rect.top = rect.left = 0;

	// Create bitmap
	CClientDC	dc (this);
	CDC 		memDC;

	if(!memDC.CreateCompatibleDC(&dc))
		return NULL;

	CBitmap bitmap;
	if(!bitmap.CreateCompatibleBitmap(&dc, rect.Width(), rect.Height()))
		return NULL;

	CBitmap* pOldMemDCBitmap = memDC.SelectObject( &bitmap );
	CFont* pOldFont = memDC.SelectObject(GetFont());

	memDC.FillSolidRect(&rect, RGB(0, 255, 0)); // Here green is used as mask color
	memDC.SetTextColor(GetSysColor(COLOR_GRAYTEXT));
	memDC.TextOut(rect.left, rect.top, GetItemText(hItem));

	memDC.SelectObject( pOldFont );
	memDC.SelectObject( pOldMemDCBitmap );

	// Create imagelist
	CImageList* pImageList = new CImageList;
	pImageList->Create(rect.Width(), rect.Height(),
	 ILC_COLOR | ILC_MASK, 0, 1);
	pImageList->Add(&bitmap, RGB(0, 255, 0)); // Here green is used as mask color

	return pImageList;
}