[AD] vidpages idea

["Robin Burrows" <rburrows@xxxxxxxxxx>]

I didn't really get a reply to my vidpages post (attached for ref.) but
here's another idea:

set_gfx_mode (w, h, vw, vh);

Why not use vw for number of videopages as 2 or 3 are still valid for
minimum width? This would nicely fix the problem of not knowing how many
pages to allocate (and is easy to add to the win driver).

My other post:
Some gfx drivers have problems with the current windows bodge of allocating
3 video pages that causes pageflip to flicker. This is fixed by only
allocating 2 buffers, which is currently not possible as it is unknown if
the programme will use triple buffering. I am posting this here for thoughts
on the best solution:

1) Do nothing, and update the docs to explain this problem and that
programmes should always offer triple buffer (which always works) too. I was
thinking of writing a framework C file that does all the initing of gfx,
timers etc and users just include it in their project, along with their C
files and this framework will call gameinit() then gameloop() at intervals
set by the user (say 100hz, and would pageflip/tripbuf/double buf
automatically) until gameloop() returns -1 then call gameexit(). This would
solve a lot of problems allegro coders make for themselves, but I only want
to do this if there is a good chance it will be put in the Allegro library
distro.

2) Add a var or set_video_pages (int numpages); function (like
set_color_depth) to be called before set_gfx_mode.

3) Use a scheme like the older allegro virtualpage pageflip:
set_gfx_mode (GFX_AUTODETECT, 640, 480, 0, 0); //use current method, alloc 2
bb
set_gfx_mode (GFX_AUTODETECT, 640, 480, 640, 960); //alloc 1 bb (pageflip)
set_gfx_mode (GFX_AUTODETECT, 640, 480, 640, 1440); //alloc 2 bb (triple
buf)
This should be clearly mentioned and explained in the docs and examples.
Also mention the first calls to create_video_bitmap should be for the vid
pages.

4) Allocate 2 pages (1 backbuffer) so pageflip works on call to
set_gfx_mode, then release DD and re-init DD with 2 backbuffers if it turns
out a 2nd is needed for triple buffer (3rd call to create_video_bitmap with
screen dimensions with no intervening call(s) to create_video_bitmap with <>
screen dimensions). "Nightmare!" - Eric Botcazou

Robin