X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?p=dosdemo;a=blobdiff_plain;f=README.md;h=b3a41a1e2e394608b01c718de18a05340b331d35;hp=102090e24e0ec3dc198f7e7bcb14f90990a5b17f;hb=59c564d8a2077ce90e7c83fdb276b80c9bfa238c;hpb=c1029b14c3fde9c98d524f17201364c695b6b117

diff --git a/README.md b/README.md
index 102090e..b3a41a1 100644
--- a/README.md
+++ b/README.md
@@ -1,8 +1,17 @@
 Unnamed Mindlapse DOS demo for Pentium 133
 ------------------------------------------
 The demo requires VESA Bios Extensions (VBE) 2.0. If your graphics card doesn't
-support VBE 2.0 or greater, then make sure to run the `univbe` TSR first, or
-the demo will fail to find a usable LFB video mode.
+support VBE 2.0 or greater, then make sure to load the `univbe` TSR first.
+
+Source structure
+----------------
+ - src/          cross-platform demo framework and miscellaneous utility code
+ - src/scr/      demo screens (parts) and effects support code
+ - src/dos/      DOS platform code
+ - src/sdl/      SDL 1.x platform code (windows/UNIX version)
+ - libs/cgmath/  math library, header-file only
+ - libs/imago/   image loading library (includes libpng, zlib, libjpeg)
+ - libs/anim/    keyframe animation library
 
 Building on DOS with Watcom
 ---------------------------
@@ -120,3 +129,21 @@ U-only pairable instructions:
  - adc, sbb
  - shr, sar, shl, sal with immediate
  - ror, rol, rcr, rcl with immediate=1
+
+Notes about DJGPP & CWSDPMI
+---------------------------
+Can't use the `hlt` instruction for waiting for interrupts, because we're
+running in ring3 by default. I surrounded all the `hlt` instructions with a
+`USE_HLT` conditional, which is undefined when building with DJGPP.
+
+It's possible to arrange for our code to run on ring0 by changing the DPMI
+provider from `cwsdpmi.exe` to `cwsdpr0.exe` by running:
+`stubedit demo.exe dpmi=cwsdpr0.exe`, but I haven't tested under win9x to see if
+it still works if we do that.
+
+Our fucking segments don't start at 0 ... to access arbitrary parts of physical
+memory we need to call `__djgpp_nearptr_enable()` and use the following macros I
+defined in `cdpmi.h`:
+
+    #define virt_to_phys(v)	((v) + __djgpp_base_address)
+    #define phys_to_virt(p)	((p) - __djgpp_base_address)