Add SDL3 GPU backend (Vulkan/Metal) with OpenGL fallback

src/rendering/shader_backend.cpp

@@ -0,0 +1,99 @@
+#include "rendering/shader_backend.hpp"
+
+#include <algorithm>
+#include <fstream>
+#include <sstream>
+
+namespace Rendering {
+
+    namespace {
+
+        auto trimString(const std::string& str) -> std::string {
+            const std::size_t start = str.find_first_not_of(" \t\r\n");
+            const std::size_t end = str.find_last_not_of(" \t\r\n");
+            if (start != std::string::npos && end != std::string::npos) {
+                return str.substr(start, end - start + 1);
+            }
+            return "";
+        }
+
+    }  // namespace
+
+    auto loadFileToString(const std::filesystem::path& path, std::string& out) -> bool {
+        std::ifstream ifs(path, std::ios::in | std::ios::binary);
+        if (!ifs) { return false; }
+        std::ostringstream ss;
+        ss << ifs.rdbuf();
+        out = ss.str();
+        return true;
+    }
+
+    auto parseMetaFile(const std::filesystem::path& meta_path) -> ShaderMetadata {
+        ShaderMetadata metadata;
+        std::ifstream ifs(meta_path);
+        if (!ifs) { return metadata; }
+
+        std::string line;
+        while (std::getline(ifs, line)) {
+            const std::size_t colon = line.find(':');
+            if (colon == std::string::npos) { continue; }
+
+            std::string key = line.substr(0, colon);
+            std::string value = trimString(line.substr(colon + 1));
+
+            std::transform(key.begin(), key.end(), key.begin(),
+                [](unsigned char c) { return static_cast<char>(std::tolower(c)); });
+            key = trimString(key);
+
+            if (key == "name") { metadata.name = value; }
+            else if (key == "author") { metadata.author = value; }
+            else if (key == "ichannel0") { metadata.iChannel0 = value; }
+            else if (key == "ichannel1") { metadata.iChannel1 = value; }
+            else if (key == "ichannel2") { metadata.iChannel2 = value; }
+            else if (key == "ichannel3") { metadata.iChannel3 = value; }
+        }
+        return metadata;
+    }
+
+    auto extractShaderMetadata(const std::string& source) -> ShaderMetadata {
+        ShaderMetadata metadata;
+
+        std::istringstream stream(source);
+        std::string line;
+        int line_count = 0;
+        constexpr int MAX_LINES_TO_CHECK = 30;
+
+        while (std::getline(stream, line) && line_count < MAX_LINES_TO_CHECK) {
+            line_count++;
+
+            const std::size_t pos = line.find("//");
+            if (pos == std::string::npos) { continue; }
+
+            const std::string comment = line.substr(pos + 2);
+            std::string lower = comment;
+            std::transform(lower.begin(), lower.end(), lower.begin(),
+                [](unsigned char c) { return static_cast<char>(std::tolower(c)); });
+
+            auto valueAfterColon = [&]() {
+                return trimString(comment.substr(comment.find(':') + 1));
+            };
+
+            if (lower.find("name:") != std::string::npos) {
+                metadata.name = valueAfterColon();
+            } else if (lower.find("author:") != std::string::npos) {
+                metadata.author = valueAfterColon();
+            } else if (lower.find("ichannel0:") != std::string::npos) {
+                metadata.iChannel0 = valueAfterColon();
+            } else if (lower.find("ichannel1:") != std::string::npos) {
+                metadata.iChannel1 = valueAfterColon();
+            } else if (lower.find("ichannel2:") != std::string::npos) {
+                metadata.iChannel2 = valueAfterColon();
+            } else if (lower.find("ichannel3:") != std::string::npos) {
+                metadata.iChannel3 = valueAfterColon();
+            }
+        }
+
+        return metadata;
+    }
+
+}  // namespace Rendering