控件背景透明代码

procedure DrawParentBackground(Control: TControl; DC: HDC; R: PRect = nil; bDrawErasebkgnd: Boolean = False);
var
SaveIndex: Integer;
MemDC: HDC;
MemBmp: HBITMAP;
begin
if R <> nil then
begin
MemDC := CreateCompatibleDC(DC);
MemBmp := CreateCompatibleBitmap(DC, Control.Width, Control.Height);
SelectObject(MemDC, MemBmp);
try
with Control.BoundsRect.TopLeft do
SetWindowOrgEx(MemDC, X, Y, nil);
if bDrawErasebkgnd then
Control.Parent.Perform(WM_ERASEBKGND, Integer(MemDC), Integer(MemDC));
Control.Parent.Perform(WM_PAINT, Integer(MemDC), Integer(MemDC));
with Control.BoundsRect.TopLeft do
BitBlt(DC, R^.Left, R^.Top, R^.Right - R^.Left, R^.Bottom - R^.Top, MemDC, X + R^.Left, Y + R^.Top, SRCCOPY);
finally
DeleteObject(MemBmp);
DeleteDC(MemDC);
end;
Exit;
end;
SaveIndex := SaveDC(DC);
try
with Control.BoundsRect.TopLeft do
SetWindowOrgEx(DC, X, Y, nil);
if bDrawErasebkgnd then
Control.Parent.Perform(WM_ERASEBKGND, Integer(DC), Integer(DC));
Control.Parent.Perform(WM_PAINT, Integer(DC), Integer(DC));
finally
RestoreDC(DC, SaveIndex);
end;
end;