implement system fonts search for Linux

openVulkanoCpp/Host/Linux/SystemInfo.cpp

@@ -16,6 +16,9 @@
 #include <sys/utsname.h>
 #include <unistd.h>
 #include <thread>
+#include <filesystem>
+#include <functional>
+#include <map>
 
 namespace OpenVulkano
 {
@@ -397,6 +400,34 @@ namespace OpenVulkano
 
 	std::string SystemInfo::GetSystemFontPath(const std::string& fontName)
 	{ 
+		// fontName -> fontPath
+		static std::map<std::string, std::string> fontFilesMapping;
+		if (fontFilesMapping.empty())
+		{
+			const std::filesystem::path fontsDir = "/usr/share/fonts/truetype";
+			std::function<void(const std::filesystem::path)> GetFontFiles;
+			GetFontFiles = [&](const std::filesystem::path& dir)
+			{
+				for (const auto& file : std::filesystem::directory_iterator(dir))
+				{
+					if (file.is_directory())
+					{
+						GetFontFiles(dir / file);
+					}
+					else if (file.path().extension() == ".ttf")
+					{
+						// store font name without extension
+						fontFilesMapping[file.path().stem()] = file.path();
+					}
+				}
+			};
+			GetFontFiles(fontsDir);
+		}
+
+		if (fontFilesMapping.contains(fontName))
+		{
+			return fontFilesMapping.at(fontName);
+		}
 		return "";
 	}