nanogui: How pixmaps will work
Subject:
Re: How pixmaps will work
From:
richardk ####@####.####
Date:
16 Oct 1999 13:20:33 -0000
Message-Id: <380879BB.5AC9D245@crusaders.no>
> >I was referring more to the time/space tradeoff. Keeping bitmaps offscreen
> >will require more memory, doing redraws will require more CPUs. This
> >decision is more important in embedded systems than in larger machines.
> It's not as if it's something that is forced on you. But for many applications
> offscreen pixmaps is a must to get decent performance.
Vidar is right. Nothing suck up more time that writing to screen-memory.
keep in mind that you cant write to display memory while it is being read by some
other device.
I read somewhere ( in a book my Michael Abrash ) that you only get 10 - 20 % of a
complete cycle to write to memory on.
This cause a rather big delay, since the cpu usually wait until it is allowed to
write to that memory.
Offscreen you only get the memory refresh penalty, and the blit itself is so fast
you usually manage to blit everything in that small amount of time we got before
memory is being read again
Keep in mind I am a little out of date on the hardware side, static ram might make
my knowledge obsolete. =)
-Richard
