Add configurable Renderer backend

There are still some initialization errors to work through, such as
config not being initialized properly by the time GPU tries to utilize
it too. Also some life-time issues. But manually forcing it to use the
Null backnd successfully works and allows games to be "played"
headlessly.

include/config.hpp

@@ -1,9 +1,12 @@
 #pragma once
 #include <filesystem>
 
+#include "renderer.hpp"
+
 // Remember to initialize every field here to its default value otherwise bad things will happen
 struct EmulatorConfig {
 	bool shaderJitEnabled = false;
+	RendererType rendererType = RendererType::OpenGL;
 
 	void load(const std::filesystem::path& path);
 	void save(const std::filesystem::path& path);

include/emulator.hpp

@@ -70,8 +70,8 @@ class Emulator {
   public:
 	// Decides whether to reload or not reload the ROM when resetting. We use enum class over a plain bool for clarity.
 	// If NoReload is selected, the emulator will not reload its selected ROM. This is useful for things like booting up the emulator, or resetting to
-	// change ROMs. If Reload is selected, the emulator will reload its selected ROM. This is useful for eg a "reset" button that keeps the current ROM
-	// and just resets the emu
+	// change ROMs. If Reload is selected, the emulator will reload its selected ROM. This is useful for eg a "reset" button that keeps the current
+	// ROM and just resets the emu
 	enum class ReloadOption { NoReload, Reload };
 
 	Emulator();

include/renderer.hpp

@@ -6,6 +6,12 @@
 #include "PICA/regs.hpp"
 #include "helpers.hpp"
 
+enum class RendererType : s8 {
+	// Todo: Auto = -1,
+	Null = 0,
+	OpenGL = 1,
+};
+
 class GPU;
 
 class Renderer {

src/config.cpp

@@ -31,6 +31,7 @@ void EmulatorConfig::load(const std::filesystem::path& path) {
 		if (gpuResult.is_ok()) {
 			auto gpu = gpuResult.unwrap();
 
+			rendererType = RendererType(toml::find_or<toml::integer>(gpu, "Renderer", int64_t(rendererType)));
 			shaderJitEnabled = toml::find_or<toml::boolean>(gpu, "EnableShaderJIT", false);
 		}
 	}
@@ -54,6 +55,7 @@ void EmulatorConfig::save(const std::filesystem::path& path) {
 		printf("Saving new configuration file %s\n", path.string().c_str());
 	}
 
+	data["GPU"]["Renderer"] = static_cast<s8>(rendererType);
 	data["GPU"]["EnableShaderJIT"] = shaderJitEnabled;
 
 	std::ofstream file(path, std::ios::out);

src/core/PICA/gpu.cpp

@@ -7,7 +7,7 @@
 
 #include "PICA/float_types.hpp"
 #include "PICA/regs.hpp"
-
+#include "renderer_null/renderer_null.hpp"
 #ifdef PANDA3DS_ENABLE_OPENGL
 #include "renderer_gl/renderer_gl.hpp"
 #endif
@@ -20,10 +20,22 @@ GPU::GPU(Memory& mem, EmulatorConfig& config) : mem(mem), config(config) {
 	vram = new u8[vramSize];
 	mem.setVRAM(vram);  // Give the bus a pointer to our VRAM
 
-	// TODO: Configurable backend
+	switch (config.rendererType) {
+		case RendererType::Null: {
+			renderer.reset(new RendererNull(*this, regs));
+			break;
+		}
 #ifdef PANDA3DS_ENABLE_OPENGL
-	renderer.reset(new RendererGL(*this, regs));
+		case RendererType::OpenGL: {
+			renderer.reset(new RendererGL(*this, regs));
+			break;
+		}
 #endif
+		default: {
+			Helpers::panic("Invalid rendering backend index: %d", static_cast<s8>(config.rendererType));
+			break;
+		}
+	}
 }
 
 void GPU::reset() {

src/emulator.cpp

@@ -26,24 +26,26 @@ Emulator::Emulator() : kernel(cpu, memory, gpu), cpu(memory, kernel), gpu(memory
 	}
 
 #ifdef PANDA3DS_ENABLE_OPENGL
-	// Request OpenGL 4.1 Core (Max available on MacOS)
-	// MacOS gets mad if we don't explicitly demand a core profile
-	SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
-	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 4);
-	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 1);
-	window = SDL_CreateWindow("Alber", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, width, height, SDL_WINDOW_OPENGL);
+	if (config.rendererType == RendererType::OpenGL) {
+		// Request OpenGL 4.1 Core (Max available on MacOS)
+		// MacOS gets mad if we don't explicitly demand a core profile
+		SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
+		SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 4);
+		SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 1);
+		window = SDL_CreateWindow("Alber", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, width, height, SDL_WINDOW_OPENGL);
 
-	if (window == nullptr) {
-		Helpers::panic("Window creation failed: %s", SDL_GetError());
-	}
+		if (window == nullptr) {
+			Helpers::panic("Window creation failed: %s", SDL_GetError());
+		}
 
-	glContext = SDL_GL_CreateContext(window);
-	if (glContext == nullptr) {
-		Helpers::panic("OpenGL context creation failed: %s", SDL_GetError());
-	}
+		glContext = SDL_GL_CreateContext(window);
+		if (glContext == nullptr) {
+			Helpers::panic("OpenGL context creation failed: %s", SDL_GetError());
+		}
 
-	if (!gladLoadGL(reinterpret_cast<GLADloadfunc>(SDL_GL_GetProcAddress))) {
-		Helpers::panic("OpenGL init failed: %s", SDL_GetError());
+		if (!gladLoadGL(reinterpret_cast<GLADloadfunc>(SDL_GL_GetProcAddress))) {
+			Helpers::panic("OpenGL init failed: %s", SDL_GetError());
+		}
 	}
 #endif
 
@@ -56,7 +58,6 @@ Emulator::Emulator() : kernel(cpu, memory, gpu), cpu(memory, kernel), gpu(memory
 		}
 	}
 
-	config.load(std::filesystem::current_path() / "config.toml");
 	reset(ReloadOption::NoReload);
 }
 

src/main.cpp

@@ -1,9 +1,9 @@
 #include "emulator.hpp"
 
-int main (int argc, char *argv[]) {
-    Emulator emu;
+int main(int argc, char *argv[]) {
+	Emulator emu;
 
-    emu.initGraphicsContext();
+	emu.initGraphicsContext();
 
 	if (argc > 1) {
 		auto romPath = std::filesystem::current_path() / argv[1];