OpenJKDF2 is usable as a hook-and-replace DLL with the original JK.EXE (v1.0) to allow for quality-of-life improvements and multiplayer, since the SDL2 and 64-bit versions do not currently have DirectPlay functions implemented.
df2_reimpl supports both the KVM target (OpenJKDF2-KVM) as well as WINE/Windows, though no guarantees are made for the addition of jkgfxmod, nor other patches and hooks. Since KVM has some issues with imports/exports and stdlib, df2_reimpl_kvm.dll is compiled with -Wl,-e_hook_init -nostartfiles, while df2_reimpl.dll is compiled without those linker flags.
Hooking is done by patching JK.EXE with JK-hook.ips (using Lunar IPS or similar). This patch replaces Window_Main at offset 0x10db50 with the following:
68 70 E7 50 00 FF 15 98 05 8F 00 68 80 E7 50 00 50 FF 15 1C 05 8F 00 FF E0 C3 00 00 00 00 00 00 64 66 32 5F 72 65 69 6D 70 6C 2E 64 6C 6C 00 00 68 6F 6F 6B 5F 69 6E 69 74 5F 77 69 6E 00 00 00
which is just some small shellcode for
int (*v1)(void);
v1 = GetProcAddress(LoadLibraryA("df2_reimpl.dll"), "hook_init_win");
return v1();
OpenJKDF2 then calls the necessary VirtualProtect functions from hook_init_win, hooks all the functions it needs and then calls its own implementation of Window_Main which was replaced with the loader.
TL;DR for Windows users
- Patch JK.EXE with
JK-hook.ips - Compile df2_reimpl with
make - Copy
df2_reimpl.dllto the same folder asJK.EXE