Switch Dreamcast to GPF SDL for DMA video and hardware palette

Replace kos-ports SDL with GPF SDL (SDL-dreamhal--GLDC) which provides
PVR DMA framebuffer transfer and native 8bpp hardware palette support.
This bypasses the manual 8bpp-to-16bpp conversion in dc_video.cpp,
roughly doubling framerate from ~20-25 to ~40-50 FPS.

Signed-off-by: Panagiotis Georgiadis <pgeorgia@redhat.com>

Author: drpaneas

CMake/platforms/dreamcast.cmake

@@ -24,6 +24,12 @@ set(DEFAULT_AUDIO_RESAMPLING_QUALITY 0)
 set(DEFAULT_PER_PIXEL_LIGHTING 0)
 set(DEVILUTIONX_PALETTE_TRANSPARENCY_BLACK_16_LUT ON CACHE BOOL "" FORCE)
 
+# GPF SDL supports 8bpp with hardware palette - lets SDL handle the
+# palette-to-RGB conversion internally via PVR DMA, avoiding the
+# manual 8bpp->16bpp conversion in dc_video.cpp entirely.
+set(SDL1_VIDEO_MODE_BPP 8)
+set(SDL1_VIDEO_MODE_FLAGS SDL_DOUBLEBUF|SDL_HWSURFACE)
+
 set(DEFAULT_WIDTH 640)
 set(DEFAULT_HEIGHT 480)
 
@@ -32,11 +38,12 @@ set(UNPACKED_SAVES ON)
 
 set(DEVILUTIONX_GAMEPAD_TYPE Generic)
 
-set(JOY_BUTTON_A 0)
+# GPF SDL button IDs (from SDL_dreamcast.h SDL_DC_button enum)
+set(JOY_BUTTON_A 2)
 set(JOY_BUTTON_B 1)
-set(JOY_BUTTON_X 2)
-set(JOY_BUTTON_Y 3)
-set(JOY_BUTTON_START 4)
+set(JOY_BUTTON_X 5)
+set(JOY_BUTTON_Y 6)
+set(JOY_BUTTON_START 3)
 
 set(JOY_HAT_DPAD_UP_HAT 0)
 set(JOY_HAT_DPAD_DOWN_HAT 0)

CMake/platforms/dreamcast.toolchain.cmake

@@ -15,10 +15,11 @@ set(DREAMCAST ON)
 
 # 3. Add our include paths
 # KOS ports often hide headers in subdirectories
+# GPF SDL installs to KOS_BASE/addons/include/dreamcast/SDL/
 list(APPEND CMAKE_INCLUDE_PATH
     "$ENV{KOS_PORTS}/include/zlib"
     "$ENV{KOS_PORTS}/include/bzlib"
-    "$ENV{KOS_PORTS}/include/SDL"
+    "$ENV{KOS_BASE}/addons/include/dreamcast/SDL"
 )
 
 # 4. Force libraries (The "Nuclear Option" for sub-projects)
@@ -28,9 +29,10 @@ set(ZLIB_LIBRARY "$ENV{KOS_PORTS}/lib/libz.a" CACHE FILEPATH "ZLIB Library" FORC
 set(BZIP2_INCLUDE_DIR "$ENV{KOS_PORTS}/include/bzlib" CACHE PATH "BZip2 Include Dir" FORCE)
 set(BZIP2_LIBRARIES "$ENV{KOS_PORTS}/lib/libbz2.a" CACHE FILEPATH "BZip2 Library" FORCE)
 
-# 5. Force SDL1 - MUST set SDL_LIBRARY without -lpthreads (KOS has built-in threading)
-set(SDL_INCLUDE_DIR "$ENV{KOS_PORTS}/include/SDL" CACHE PATH "SDL Include Dir" FORCE)
-set(SDL_LIBRARY "$ENV{KOS_PORTS}/lib/libSDL.a" CACHE FILEPATH "SDL Library" FORCE)
+# 5. Force SDL1 - GPF SDL (SDL-dreamhal--GLDC) for DMA video and hardware palette
+# GPF SDL installs via its Makefile.dc to KOS_BASE/addons/{lib,include}/dreamcast/
+set(SDL_INCLUDE_DIR "$ENV{KOS_BASE}/addons/include/dreamcast/SDL" CACHE PATH "SDL Include Dir" FORCE)
+set(SDL_LIBRARY "$ENV{KOS_BASE}/addons/lib/dreamcast/libSDL.a" CACHE FILEPATH "SDL Library" FORCE)
 
 # 6. Fix libfmt and magic_enum compilation
 # Disable long double support because sh4-gcc's long double (64-bit) confuses libfmt

Packaging/dreamcast/.gitignore

@@ -35,6 +35,9 @@ File[0-9]*.xxx
 File[0-9]*.gif
 File[0-9]*.smk
 
+# GPF SDL source (cloned by build.sh)
+SDL-gpf/
+
 # Build tool output
 *.o
 

Packaging/dreamcast/build.sh

@@ -30,6 +30,21 @@ if [ ! -x "${MKDCDISC}" ]; then
     exit 1
 fi
 
+GPF_SDL_DIR="${SCRIPT_DIR}/SDL-gpf"
+GPF_SDL_LIB="${KOS_BASE}/addons/lib/dreamcast/libSDL.a"
+
+if [ ! -f "${GPF_SDL_LIB}" ]; then
+    echo "Building GPF SDL (SDL-dreamhal--GLDC) for DMA video..."
+    if [ ! -d "${GPF_SDL_DIR}" ]; then
+        git clone --depth 1 -b SDL-dreamhal--GLDC \
+            https://github.com/GPF/SDL-1.2 "${GPF_SDL_DIR}"
+    fi
+    make -C "${GPF_SDL_DIR}" -f Makefile.dc -j"$(nproc 2>/dev/null || sysctl -n hw.ncpu 2>/dev/null || echo 4)"
+    echo "GPF SDL installed to ${GPF_SDL_LIB}"
+else
+    echo "GPF SDL already installed at ${GPF_SDL_LIB}"
+fi
+
 rm -rf "${BUILD_DIR}"
 mkdir -p "${BUILD_DIR}"
 

Source/utils/display.cpp

@@ -63,6 +63,10 @@
 #endif
 #endif
 
+#ifdef __DREAMCAST__
+#include <SDL_dreamcast.h>
+#endif
+
 namespace devilution {
 
 extern SDLSurfaceUniquePtr RendererTextureSurface; /** defined in dx.cpp */
@@ -485,6 +489,13 @@ void SetVideoModeToPrimary(bool fullscreen, int width, int height)
 #ifdef __3DS__
 	flags &= ~SDL_FULLSCREEN;
 	flags |= Get3DSScalingFlag(*GetOptions().Graphics.fitToScreen, width, height);
+#endif
+#ifdef __DREAMCAST__
+	SDL_DC_SetVideoDriver(SDL_DC_DMA_VIDEO);
+	SDL_DC_VerticalWait(SDL_FALSE);
+	SDL_DC_ShowAskHz(SDL_FALSE);
+	SDL_DC_EmulateKeyboard(SDL_FALSE);
+	SDL_DC_EmulateMouse(SDL_FALSE);
 #endif
 	SetVideoMode(width, height, SDL1_VIDEO_MODE_BPP, flags);
 	if (OutputRequiresScaling())