SDL2 port for DOS (DJGPP and VBE 2.0+) #13906
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Timers remain unsupported due to lack of multithreading.
A few other minor style things were tweaked too.
This implementation is probably wrong, but it lays the foundation for doing it better, eventually.
Windows are now always created with the fullscreen flag.
It ain't pretty though!
Key release events do not seem to be visible via _bios_keybrd. This will probably change to use a keyboard interrupt handler.
It doesn't seem to be necessary.
Example toolchain file:
```bash
set(CMAKE_SYSTEM_NAME Generic)
set(CMAKE_SYSTEM_VERSION 1)
if($ENV{DJGPP_PREFIX})
set(DJGPP_PREFIX "$ENV{DJGPP_PREFIX}")
else()
set(DJGPP_PREFIX "/opt/i386-pc-msdosdjgpp-toolchain")
endif()
set(CMAKE_C_COMPILER "${DJGPP_PREFIX}/bin/i386-pc-msdosdjgpp-gcc")
set(CMAKE_CXX_COMPILER "${DJGPP_PREFIX}/bin/i386-pc-msdosdjgpp-g++")
set(CMAKE_STRIP "${DJGPP_PREFIX}/bin/i386-pc-msdosdjgpp-strip")
set(PKG_CONFIG_EXECUTABLE "${DJGPP_PREFIX}/bin/i386-pc-msdosdjgpp-pkg-config" CACHE STRING "Path to pkg-config")
set(CMAKE_EXE_LINKER_FLAGS_INIT "-static")
set(DJGPP_ROOT "${DJGPP_PREFIX}/i386-pc-msdosdjgpp")
set(CMAKE_FIND_ROOT_PATH "${DJGPP_ROOT}")
set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)
link_directories("${DJGPP_ROOT}/lib")
include_directories(BEFORE SYSTEM "${DJGPP_ROOT}/sys-include" "${DJGPP_ROOT}/include")
```
Example invocation:
```bash
cmake -S. -Bbuild-dos -DCMAKE_TOOLCHAIN_FILE="path/to/djcpp.toolchain.cmake" -DDOS=ON
```
Makes the arrow keys and page up/down work.
Basic TEXTINPUT event firing that assumes US keyboard layout.
This allows S3 trio video cards to work
Calling out via real-mode bridge would kill performance when color cycling. Luckily, VBE 2.0 provides protected mode interface for some of the functions, and setting the palette is one of them. The asm code is based on Allegro 4.2 `vesa_set_palette_range`. Luckily, Allegro license is extremely permissive.
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I have a from-scratch DOS port of SDL3 sitting in https://github.com/icculus/SDL/tree/sdl3-dos ... we should compare notes. |
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@icculus That's awesome! I've had a look at your branch:
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palettized 8bpp is still supported in SDL3 |
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What a bunch of mad lads 🤠. I know it's not relevant for your Diablo port, but I also had a branch off my VBE work that was for plain old VGA mode 13h. It could serve as a fallback if VBE isn't available for increased compatibility. It keeps its back buffer in RAM (not VGA) though, so it's not as optimal as page-flipping with VBE. I recently migrated the game I'm working on from SDL 2 to 3, so I guess I'll have to check out @icculus's branch now. 👀 |
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A similar solution could be used for supporting vba 2.0 or systems with no double buffer modes |
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So which one of us is going to be the first to hook the timer interrupt and implement threading? :) |
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@AJenbo and I took @jayschwa's SDL2 DOS port from a few years ago, rebased it onto the current SDL2, and got palettized output and keyboard fully working.
I understand that the current SDL development focuses on SDL3. I'm posting this PR here for visibility, in case someone might be interested in using it, improving it further, or forward-porting it to SDL3.
Supported
Not supported
Here is a screenshot of DevilutionX running in DOSBox. We also tested on real hardware (hit and miss depending on the graphics card).
The performance is pretty good when using the 640x480 8-bit palettized mode.
Building instructions are here in the "DOS" section: https://github.com/diasurgical/DevilutionX/blob/master/docs/building.md