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In lugnet.robotics.nxt, John Hansen wrote:
> Unfortunately, there isn't really an easier way to clear the screen other than
> to use some sort of system call which draws on the screen. That's because only
> those system calls set the display as "dirty" and if that doesn't happen then
> the firmware will not do the right thing when you draw directly to the screen
> memory. There isn't any way to directly set the dirty flag because it is not
> exposed via the IOMAP structure.
>
> John Hansen
Thanks for your response, John.
That tip about the dirty flag not being IOMAPpable is very, very useful; I could
have wasted a lot of time working that out the hard way.
I'm working on a graphical display widget to show a 'radar' (well, sonar) screen
on a portion of the full screen. I was trying to figure out how to cleanly and
quickly redraw the radar screen when new data became available.
My experience with the IOMAP calls is that they're pretty slow - it must be
doing some costly address lookup each time? Anyway, I'm leaning toward storing
a <=800 byte copy of screen memory down in local memory, and just making one to
eight syscalls to copy the relevant portions, rather than trying to write a
smaller but significant number of individual bytes.
I guess I should do some time trials to test this theory out :)
Just received my rechargeable battery, colour sensor and compass. Time for
mischief.
Jeff Elliott
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Message has 1 Reply:
Message is in Reply To:
 | | Re: What do these macros do?
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| (...) Lots of very cool stuff deleted. Sorry I missed your original message, Jeff. You can write to both the Normal and Popup screen memory and toggle back and forth between which one gets displayed. This code flips between the two buffers for 10 (...) (18 years ago, 16-Jan-07, to lugnet.robotics.nxt, lugnet.robotics)
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