From a7e5e42a188f9e6ab13706a15e6b50f36f0e00e8 Mon Sep 17 00:00:00 2001
From: rtk0c <mail.tianyig@gmail.com>
Date: Sun, 28 Mar 2021 15:13:05 -0700
Subject: Fix backend compiling/loading mechanism

---
 core/src/Entrypoint/main.cpp | 135 ++++++++++++++++++++++++++++---------------
 1 file changed, 90 insertions(+), 45 deletions(-)

(limited to 'core/src/Entrypoint/main.cpp')

diff --git a/core/src/Entrypoint/main.cpp b/core/src/Entrypoint/main.cpp
index 3adf757..b82214d 100644
--- a/core/src/Entrypoint/main.cpp
+++ b/core/src/Entrypoint/main.cpp
@@ -13,9 +13,98 @@
 #include <argparse/argparse.hpp>
 #include <iostream>
 #include <memory>
+#include <stdexcept>
 #include <string>
+#include <string_view>
 
 using namespace std::literals::string_literals;
+using namespace std::literals::string_view_literals;
+
+static std::unique_ptr<RenderingBackend> CreateDefaultBackend() {
+#if PLATFORM_WIN32
+#	if BUILD_CORE_WITH_DX12_BACKEND
+	try {
+		auto backend = std::make_unique<DirectX12Backend>();
+		return backend;
+	} catch (const std::exception&) {
+	}
+#	elif BUILD_CORE_WITH_DX11_BACKEND
+	try {
+		auto backend = std::make_unique<DirectX11Backend>();
+		return backend;
+	} catch (const std::exception&) {
+	}
+#	elif BUILD_CORE_WITH_VULKAN_BACKEND
+	try {
+		auto backend = std::make_unique<VulkanBackend>();
+		return backend;
+	} catch (const std::exception&) {
+	}
+#	elif BUILD_CORE_WITH_OPENGL3_BACKEND
+	try {
+		auto backend = std::make_unique<OpenGL3Backend>();
+		return backend;
+	} catch (const std::exception&) {
+	}
+#	elif BUILD_CORE_WITH_OPENGL2_BACKEND
+	try {
+		auto backend = std::make_unique<OpenGL2Backend>();
+		return backend;
+	} catch (const std::exception&) {
+	}
+#	endif
+#elif PLATFORM_MACOS
+	// We currently only support using metal on macos
+	backend = std::make_unique<MetalBackend>();
+#elif PLATFORM_LINUX
+#	if BUILD_CORE_WITH_VULKAN_BACKEND
+	try {
+		auto backend = std::make_unique<VulkanBackend>();
+		return backend;
+	} catch (const std::exception&) {
+	}
+#	elif BUILD_CORE_WITH_OPENGL3_BACKEND
+	try {
+		auto backend = std::make_unique<OpenGL3Backend>();
+		return backend;
+	} catch (const std::exception&) {
+	}
+#	elif BUILD_CORE_WITH_OPENGL2_BACKEND
+	try {
+		auto backend = std::make_unique<OpenGL2Backend>();
+		return backend;
+	} catch (const std::exception&) {
+	}
+#	endif
+#endif
+
+	return nullptr;
+}
+
+static std::unique_ptr<RenderingBackend> CreateBackend(std::string_view option) {
+	if (option == "default") {
+		return CreateDefaultBackend();
+	} else if (option == "opengl2") {
+		return std::make_unique<OpenGL2Backend>();
+	} else if (option == "opengl3") {
+		return std::make_unique<OpenGL3Backend>();
+	} else if (option == "vulkan") {
+		return std::make_unique<VulkanBackend>();
+	} else if (option == "dx11") {
+		return std::make_unique<DirectX11Backend>();
+	} else if (option == "dx12") {
+		return std::make_unique<DirectX12Backend>();
+	} else if (option == "metal") {
+		return std::make_unique<MetalBackend>();
+	} else {
+		std::string message;
+		message += "Unknown backend '";
+		message += option;
+		message += "'.\n";
+		throw std::runtime_error(message);
+		return nullptr;
+	}
+}
 
 int main(int argc, char* argv[]) {
 	argparse::ArgumentParser parser;
@@ -31,59 +120,15 @@ int main(int argc, char* argv[]) {
 		return -1;
 	}
 
-	std::unique_ptr<RenderingBackend> backend;
 	auto backendOption = parser.get<std::string>("--rendering-backend");
-	if (backendOption == "default") {
-		// TODO better api selection mechanism, use lower tier if higher tier is unavilable instead of bailing
-#if PLATFORM_WIN32
-#	if IMGUI_INCLUDE_DX12_BACKEND
-		backend = std::make_unique<DirectX12Backend>();
-#	elif IMGUI_INCLUDE_DX11_BACKEND
-		backend = std::make_unique<DirectX11Backend>();
-#	elif IMGUI_INCLUDE_VULKAN_BACKEND
-		backend = std::make_unique<VulkanBackend>();
-#	elif IMGUI_INCLUDE_OPENGL3_BACKEND
-		backend = std::make_unique<OpenGL3Backend>();
-#	elif IMGUI_INCLUDE_OPENGL2_BACKEND
-		backend = std::make_unique<OpenGL2Backend>();
-#	endif
-#elif PLATFORM_MACOS
-		backend = std::make_unique<MetalBackend>();
-#elif PLATFORM_LINUX
-#	if IMGUI_INCLUDE_VULKAN_BACKEND
-		backend = std::make_unique<VulkanBackend>();
-// #	elif IMGUI_INCLUDE_OPENGL3_BACKEND
-// 		backend = std::make_unique<OpenGL3Backend>();
-#	elif IMGUI_INCLUDE_OPENGL2_BACKEND
-		backend = std::make_unique<OpenGL2Backend>();
-#	endif
-#endif
-	} else if (backendOption == "opengl2") {
-		backend = std::make_unique<OpenGL2Backend>();
-	} else if (backendOption == "opengl3") {
-		backend = std::make_unique<OpenGL3Backend>();
-	} else if (backendOption == "vulkan") {
-		backend = std::make_unique<VulkanBackend>();
-	} else if (backendOption == "dx11") {
-		backend = std::make_unique<DirectX11Backend>();
-	} else if (backendOption == "dx12") {
-		backend = std::make_unique<DirectX12Backend>();
-	} else if (backendOption == "metal") {
-		backend = std::make_unique<MetalBackend>();
-	} else {
-		std::cout << "Unknown backend '" << backendOption << "'.\n";
-		return -1;
-	}
+	auto backend = CreateBackend(backendOption);
 
 	auto& io = ImGui::GetIO();
 	io.Fonts->AddFontFromFileTTF("fonts/NotoSansSC-Regular.otf", 18, nullptr, io.Fonts->GetGlyphRangesChineseSimplifiedCommon());
 
 	auto window = backend->GetWindow();
-	bool showDemo = true;
 	while (!glfwWindowShouldClose(window)) {
 		backend->BeginFrame();
-		if (showDemo)
-			ImGui::ShowDemoWindow(&showDemo);
 		backend->EndFrame();
 	}
 
-- 
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