Add string-based renderer backend configuration

Rather than using integer-indices, just use plaintext case-insensitive
names and leave the actual enum indexes as an implementation detail.

include/renderer.hpp

@@ -12,6 +12,9 @@ enum class RendererType : s8 {
 	OpenGL = 1,
 };
 
+std::optional<RendererType> fromString(std::string inString);
+const char* toString(RendererType rendererType);
+
 class GPU;
 
 class Renderer {

src/config.cpp

@@ -33,7 +33,19 @@ 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)));
+			// Get renderer
+			auto rendererResult = toml::expect<std::string>(gpu, "Renderer");
+			if (rendererResult.is_ok()) {
+				auto rendererName = rendererResult.unwrap();
+				if (auto configRendererType = fromString(rendererName); configRendererType.has_value()) {
+					rendererType = configRendererType.value();
+				} else {
+					Helpers::warn("Invalid renderer specified: %s\n", rendererName.c_str());
+				}
+			} else {
+				Helpers::warn("Renderer not specified: %s\n", rendererResult.unwrap_err());
+			}
+
 			shaderJitEnabled = toml::find_or<toml::boolean>(gpu, "EnableShaderJIT", false);
 		}
 	}
@@ -57,7 +69,7 @@ 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"]["Renderer"] = toString(rendererType);
 	data["GPU"]["EnableShaderJIT"] = shaderJitEnabled;
 
 	std::ofstream file(path, std::ios::out);

src/core/PICA/gpu.cpp

@@ -32,7 +32,7 @@ GPU::GPU(Memory& mem, EmulatorConfig& config) : mem(mem), config(config) {
 		}
 #endif
 		default: {
-			Helpers::panic("Invalid rendering backend index: %d", static_cast<s8>(config.rendererType));
+			Helpers::panic("Rendering backend not supported: %s", toString(config.rendererType));
 			break;
 		}
 	}

src/renderer.cpp

@@ -1,4 +1,24 @@
 #include "renderer.hpp"
 
+std::optional<RendererType> fromString(std::string inString) {
+	// case-insensitive
+	std::transform(inString.begin(), inString.end(), inString.begin(), [](unsigned char c) { return std::tolower(c); });
+
+	if (inString == "null")
+		return RendererType::Null;
+	else if (inString == "opengl")
+		return RendererType::OpenGL;
+
+	return std::nullopt;
+}
+
+const char* toString(RendererType rendererType) {
+	switch (rendererType) {
+		case RendererType::Null: return "null";
+		case RendererType::OpenGL: return "opengl";
+		default: return "Invalid";
+	}
+}
+
 Renderer::Renderer(GPU& gpu, const std::array<u32, regNum>& internalRegs) : gpu(gpu), regs(internalRegs) {}
 Renderer::~Renderer() {}