Re: Neil ain't so bad afterall...some explanation still needed
>
> There are few things that are needing tought some explanation...
> 1. How does mode X, vesa, and gfx modes differ from each others?
> Deltailed explanation, including working with different kinds of
> videocards/machines, needed.
Mode X should work with any VGA-compatible card, and *most* monitors.
Mode X is actually 320x200 mode 19, but with the video registers
reprogrammed with different timings to generate different resolutions.
Some older monitors do not support certain vertical frequencies and may
either blank or whine at you, or display a rolling screen. Newer
multi-syncing monitors should not have this problem. Mode X also switches
the memory layout to a planar addressing, so that the number of pixels on
the screen can be up to quadruple the amount in mode 19. A special method
of switching the registers is necessary to select the planes, and
modex_blit was written for this task.
Vesa modes are available to most super-vga cards, adding higher
resolutions than vga and hi-color(15,16bit) and true-color(24,32). Some
cards allow access to video ram through the A0000 memory segment, using an
interrupt to select which bank of ram to access. Newer cards support
mapping the whole of video memory to somewhere else in memory so it can be
accessed linearly, hence the name linear frame buffer. Banked_blit
handles banked vesa modes, and the regular blit is used for linear.
Neil also handles regular mode 19, and offers two other tweaked modes
similar to mode x, but without the yucky planar stuff. They are 256x256
resolution and 256x240 (SNES) modes. These are all addressed linearly.
> 2. are 32-bit color dephts still same than 24-bit ones?
> I saw somewhere how Neil does linear banking:
> 24-bit was something like: BBBBBBBB GGGGGGGG RRRRRRRR
> 32-bit was smthng like: BBBBBBBB GGGGGGGG RRRRRRRR XXXXXXXX
> where X was unused
Right. 32 and 24 bit modes are effectively the same. 32-bit is somewhat
faster than 24-bit, due to pixel being aligned on a 4-byte boundary.
24-bit does save space though. And most video cards I've seen only
support one or the other. It is not strictly necessary to know this to
use the library btw.
> 3.I've read neil.faq and neil.doc .... is there something else important
> I should know before adding Neil in my programs?
You need to know that Neil is free, and written in someone's spare time to
benefit other Euphoria programmers. There are also other libraries
available, such as Hawke''s TrueColor lib (originally Chris Street's), or
Mic's Mode19 lib, and can't forget Hollow Horse's mode19 lib too. Other
libraries may be easier to use or even faster in some cases (where's your
benchmarks, Hawke'?) but Neil offers the most features as far as I've
seen.
> --Tapani
Regards,
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