Speedup of rotated screen

[Staffan Ulfberg]

Matthieu Herrb <matthieu.herrb at laas.fr> writes:

> > I have been hacking a bit on getting the code that blits a rotated
> > shadow onto the display a bit faster and came up with the patch
> > available at https://bugs.freedesktop.org/show_bug.cgi?id=4537

> We also need some tests on other platforms to make sure it doesn't
> create a regression with some other drivers that support rotation.

I have a question myself about the original code: This is the function
call to get the address in the destination frame buffer to write to:

	  win = (FbBits *) (*pBuf->window) (pScreen,
					    scr_y,
					    scr_x << 2,
					    SHADOW_WINDOW_WRITE,
					    &winSize,
					    pBuf->closure);

The "scr_x << 2" part seems, to me, to assume that 
sizeof(FbBits) == 4.  Am I missing something, or is this really 
correct?  Anyway, my patch does not make this problem either better
or worse.

Staffan