Mail Archives: djgpp/1997/03/04/10:34:37
Paul Derbyshire (ao950 AT FreeNet DOT Carleton DOT CA) wrote:
: I have several questions about Allegro, mostly out of curiosity...
: * Why, when using a SVGA mode e.g. GFX_AUTODETECT 640x480, does a
: fade_in(palette) or a fade_out() seem to do 4 fades in series instead of
: just 1? Fades work as expected in GFX_MODEX. Is it a bug or a "feature"?
Most likely, you're defining the colour strenghts in your palette from
0 to 255; this is incorrect, the VGA hardware only recognises values from
0 to 63. For example, white is (63,63,63) [R,G,B], red is (63,0,0), orange
is (63,31,0), ...
: * Is the video manipulation ultimately done with super-fast nearptrs or far
: pointers? Near pointers are thought not to work on some DPMI hosts,
: so an optimal Allegro would detect the DPMI host, if it is a known safe
: one i.e. cwsdpmi use nearptrs, else use farptrs for safety...
: * What functions in allegro are typically inlined?
: * Which graphics functions use inline asm for optimisation?
Read the sources for answers to those three.
: * Was Allegro compiled with -m486?
Read the makefile.
: * When an allegro program that uses sound starts, there is a popping noise.
: The noise also happens at exit. I have learned to dread this pop, since
: usually if it happens when I'm not expecting it, I find myself staring at
: a stack dump a few seconds later. What is it?
It's your sound card; probably objecting to the change in mixer settings.
Some cards make a pop when they receive initialisation commands, some don't.
: * There is a definite link between using allegro and GCC making funny noises
: during compile. For instance, using RHIDE and Allegro, I ran a program,
: and it hit a breakpoint. I inspected a few variables, then changed some
: source and ran Make. GCC was called, and five seconds into the compile a
: bunch of queer repeating and *LOUD* sound effects started coming from my SB!
: It has happened a total of 3 times now. All 3 times after an allegro
: program a) used sound and b) never got to allegro_exit.
If the program doesn't exit smoothly, it's not surprising that it leaves
a mess. BTW my Allegro programs always seem to say "Shutting down Allegro"
when they crash; don't yours? If not, try making a short program which
initialises Allegro and the sound card, then exits. When your programs die
you can run this program, and it might tidy up a bit.
--
George Foot <gfoot AT mc31 DOT merton DOT ox DOT ac DOT uk>
Merton College, Oxford.
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