nanogui: Clearing a certain area of a window
Subject:
Re: [nanogui] Clearing a certain area of a window
From:
tj ####@####.####
Date:
1 Oct 2005 04:49:08 +0100
Message-Id: <433E0777.9020901@comcast.net>
Greg Haerr wrote:
>: Is it possible to clear only a certain rectangular area of a window
>: instead of having to use GrClearWindow()? I have used GrFillRect() when
>: the background is solid,
>
>GrClearWindow will clear just a portion of a window, and that should
>be the best choice, if the application never drew the window in the
>first place. If the application used GrFillRect, then that should be
>used to repaint.
>
>
>
I'm confused, my usual state :-). I thought GrClearWindow() basically
"wiped the window clean" leaving only the background. Whether it be a
solid color or a pixmap. How does it clear only a portion of a window
when it only takes the window id, no bounding coordinates, as an argument?
>: but what about when the background is a pixmap,
>: using GrSetBackgroundPixmap()?
>
>GrClearWindow should cause a repaint event such that the
>server executes the same code that drew the background pixmap
>in the first place, tiled, stretched, etc.
>
>
>
That is why I want it to do it.
>:
>: You could GrCopyArea() from the original pixmap to the window, but what
>: is the background is tiled, stretched, etc?
>
>No sense in duplicating server code, IMO.
>
>
>
>
Exactly
>:
>: Be whole lot quicker if it's a small area compared to the entire window.
>: Especially on a several 100Mhz embedded processor.
>
>Are you saying that GrClearWindow doesn't work, or is just
>slow?
>
>
>
No intent to throw anything off on GrClearWindow().
When I started embedded programming more years ago than I care to think
about a 2 Mhz processor was FAST (Remember 8080s, Z80s, 8048s?), and you
are always thinking about how to cut instruction cycles. So in my mind,
if you only need to clear a 200x20 pixel area on a 320x240 window (which
is 5% of total), that saves a bunch of instruction cycles (not having to
clear the other 95%) no matter how well the clearing function works or
how fast it is. Plus, not having to redraw the areas you don't want cleared.
>Regards,
>
>Greg
>
>
>
tj
