nanogui: Drawing modes
Subject:
Drawing modes
From:
Alex Holden ####@####.####
Date:
19 May 1999 00:55:16 -0000
Message-Id: <Pine.LNX.4.04.9905190136090.447-100000@hyperspace>
After spending a while reading the Allegro code, though I don't really
understand the bank code (it seems to be to do with making sure
transactions are properly aligned), it does appear that all the drawing
modes except plain old "set", do in fact read from the buffer, perform the
operation, and then write it back. So if you do an XOR draw to the Frame
buffer, for every pixel you write it reads one from the graphics device
first (well, the banking code will speed things up for hlines() if I
understand it right by reading several pixels at once, but you get the
idea). That doesn't stop you from allocating a memory buffer, performing
the operations on that, and blitting the altered regions to the screen
buffer if you want, but that isn't the way it works normally. I'm going to
get some sleep now, but I'll probably write the other drawing modes when
I get up in the morning.
--------------- Linux- the choice of a GNU generation. --------------
: Alex Holden (M1CJD)- Caver, Programmer, Land Rover nut, Radio Ham :
-------------------- http://www.linuxhacker.org/ --------------------
