Add software renderer implementation for SDL 1.2 backend

CMakeLists.txt

@@ -228,14 +228,24 @@ if(PLATFORM STREQUAL "glfw")
             $<TARGET_FILE_DIR:butterscotch>/gamecontrollerdb.txt
     )
 elseif(PLATFORM STREQUAL "sdl")
-    if (NOT ENABLE_LEGACY_GL)
-        message(FATAL_ERROR "SDL requires legacy GL!")
+    option(ENABLE_SW_RENDERER "Enable the software renderer (SDL 1.2 only)" ON)
+
+    if (NOT ENABLE_LEGACY_GL AND NOT ENABLE_SW_RENDERER)
+        message(FATAL_ERROR "SDL requires legacy GL or the software renderer!")
+    endif()
+
+    if(ENABLE_LEGACY_GL)
+        file(GLOB GL_SOURCES src/gl_legacy/*.c src/gl_common/*.c src/image/*.c)
+        target_include_directories(butterscotch PRIVATE ${CMAKE_SOURCE_DIR}/src/gl_legacy)
+        target_include_directories(butterscotch PRIVATE ${CMAKE_SOURCE_DIR}/src/gl_common)
+        target_sources(butterscotch PRIVATE ${GL_SOURCES})
+        target_include_directories(butterscotch PRIVATE ${CMAKE_SOURCE_DIR}/src/gl)
+    elseif(ENABLE_SW_RENDERER)
+        file(GLOB SWR_SOURCES src/sw/*.c src/image/*.c)
+        add_compile_definitions(ENABLE_SW_RENDERER)
+        target_sources(butterscotch PRIVATE ${SWR_SOURCES})
+        target_include_directories(butterscotch PRIVATE ${CMAKE_SOURCE_DIR}/src/sw)
     endif()
-    file(GLOB GL_SOURCES src/gl_legacy/*.c src/gl_common/*.c src/image/*.c)
-    target_include_directories(butterscotch PRIVATE ${CMAKE_SOURCE_DIR}/src/gl_legacy)
-    target_include_directories(butterscotch PRIVATE ${CMAKE_SOURCE_DIR}/src/gl_common)
-    target_sources(butterscotch PRIVATE ${GL_SOURCES})
-    target_include_directories(butterscotch PRIVATE ${CMAKE_SOURCE_DIR}/src/gl)
     target_include_directories(butterscotch PRIVATE ${CMAKE_SOURCE_DIR}/src/image)
 
     # Butterscotch VM/interpreter profiler

Makefile

@@ -39,6 +39,15 @@ ifndef DISABLE_BC17
 DEFINES += -DENABLE_BC17
 endif
 
+ifndef DISABLE_SW_RENDERER
+ifeq ($(PLATFORM),sdl)
+DEFINES += -DENABLE_SW_RENDERER
+SRCS += $(wildcard src/sw/*.c)
+INCLUDES += -Isrc/sw
+HEADERS += $(wildcard src/sw/*.h)
+endif
+endif
+
 # GNU make doesn't have a way to do OR in conditionals, stupid language for clowns
 ifndef DISABLE_LEGACY_GL
 ENABLE_GL := 1

src/sdl/main.c

@@ -1216,7 +1216,7 @@ int main(int argc, char* argv[]) {
         if (!args.headless && runner->currentRoom->speed > 0) {
             static bool fastForwardActive = false;
             static bool fastForwardTabPrev = false;
-            bool fastForwardTabNow = false;
+            bool fastForwardTabNow = RunnerKeyboard_checkPressed(runner->keyboard, '\t');
             if (args.fastForwardSpeed > 0.0 && fastForwardTabNow && !fastForwardTabPrev) {
                 fastForwardActive = !fastForwardActive;
                 lastFrameTime = (SDL_GetTicks()/1000.0f);

src/sw/defines.h

@@ -0,0 +1,8 @@
+#pragma once
+
+#define LIKELY(cond)   __builtin_expect(!!(cond), 1)
+#define UNLIKELY(cond) __builtin_expect(!!(cond), 0)
+
+#define UNUSED __attribute__ ((unused))
+#define FORCE_INLINE static inline __attribute__((always_inline))
+

src/sw/pixel_convert.h

@@ -0,0 +1,90 @@
+#pragma once
+
+#include "defines.h"
+
+// CONFIG: Change the size of a pixel.
+//
+// 32-bit: 0xAARRGGBB
+// 16-bit: 0b0RRRRRGGGGGBBBBB
+// 8-bit:  0bBBGGGRRR
+#define PIXEL_SIZE 32
+//#define PIXEL_SIZE 16
+//#define PIXEL_SIZE 8
+
+#if PIXEL_SIZE == 32
+typedef uint32_t uintpixel_t;
+#elif PIXEL_SIZE == 16
+typedef uint16_t uintpixel_t;
+#elif PIXEL_SIZE == 8
+typedef uint8_t uintpixel_t;
+#define PXL_TRANSPARENT (0b10101010)
+#else
+#error "Unknown pixel size!"
+#endif
+
+typedef union
+{
+	struct {
+		uint8_t r, g, b, a;
+	} p;
+	uint32_t l;
+}
+Pixel32ABGR;
+
+typedef union
+{
+	struct {
+		uint8_t b, g, r, a;
+	} p;
+	uint32_t l;
+}
+Pixel32ARGB;
+
+FORCE_INLINE UNUSED
+uint16_t abgr8888_to_rgb1555(uint32_t xl)
+{
+	Pixel32ABGR x;
+	x.l = xl;
+	return (x.p.b >> 3) | ((x.p.g >> 3) << 5) | ((x.p.r >> 3) << 10) | ((x.p.a >> 7) << 15);
+}
+
+FORCE_INLINE UNUSED
+uint8_t abgr8888_to_rgb332(uint32_t xl)
+{
+	Pixel32ABGR x;
+	x.l = xl;
+
+#if PIXEL_SIZE == 8
+	//check if transparent
+	if (x.p.a < 128)
+		return PXL_TRANSPARENT;
+#endif
+
+	uint8_t pxl = (x.p.r >> 5) | ((x.p.g >> 5) << 3) | ((x.p.b >> 6) << 6);
+
+#if PIXEL_SIZE == 8
+	//hacky fixup
+	if (pxl == PXL_TRANSPARENT)
+		pxl++;
+#endif
+
+	return pxl;
+}
+
+FORCE_INLINE UNUSED
+uintpixel_t swrConvertPixelTexture(uint32_t gmPixel)
+{
+#if PIXEL_SIZE == 32
+	return (gmPixel & 0xFF00FF00) | ((gmPixel & 0xFF) << 16) | ((gmPixel >> 16) & 0xFF);
+#elif PIXEL_SIZE == 16
+	return abgr8888_to_rgb1555(gmPixel);
+#elif PIXEL_SIZE == 8
+	return abgr8888_to_rgb332(gmPixel);
+#endif
+}
+
+#if PIXEL_SIZE == 8
+#define swrConvertPixel(x) swrConvertPixelTexture((x) | 0xFF000000)
+#else
+#define swrConvertPixel swrConvertPixelTexture
+#endif