From 19a117889c2db6b817af9458c04c04f324162e75 Mon Sep 17 00:00:00 2001
From: Stefan Boberg <stefan.boberg@epicgames.com>
Date: Mon, 9 Mar 2026 10:50:47 +0100
Subject: Eliminate spdlog dependency (#773)

Removes the vendored spdlog library (~12,000 lines) and replaces it with a purpose-built logging system in zencore (~1,800 lines). The new implementation provides the same functionality with fewer abstractions, no shared_ptr overhead, and full control over the logging pipeline.

### What changed

**New logging core in zencore/logging/:**
- LogMessage, Formatter, Sink, Logger, Registry - core abstractions matching spdlog's model but simplified
- AnsiColorStdoutSink - ANSI color console output (replaces spdlog stdout_color_sink)
- MsvcSink - OutputDebugString on Windows (replaces spdlog msvc_sink)
- AsyncSink - async logging via BlockingQueue worker thread (replaces spdlog async_logger)
- NullSink, MessageOnlyFormatter - utility types
- Thread-safe timestamp caching in formatters using RwLock

**Moved to zenutil/logging/:**
- FullFormatter - full log formatting with timestamp, logger name, level, source location, multiline alignment
- JsonFormatter - structured JSON log output
- RotatingFileSink - rotating file sink with atomic size tracking

**API changes:**
- Log levels are now an enum (LogLevel) instead of int, eliminating the zen::logging::level namespace
- LoggerRef no longer wraps shared_ptr - it holds a raw pointer with the registry owning lifetime
- Logger error handler is wired through Registry and propagated to all loggers on registration
- Logger::Log() now populates ThreadId on every message

**Cleanup:**
- Deleted thirdparty/spdlog/ entirely (110+ files)
- Deleted full_test_formatter (was ~80% duplicate of FullFormatter)
- Renamed snake_case classes to PascalCase (full_formatter -> FullFormatter, json_formatter -> JsonFormatter, sentry_sink -> SentrySink)
- Removed spdlog from xmake dependency graph

### Build / test impact

- zencore no longer depends on spdlog
- zenutil and zenvfs xmake.lua updated to drop spdlog dep
- zentelemetry xmake.lua updated to drop spdlog dep
- All existing tests pass, no test changes required beyond formatter class renames
---
 src/zencore/logging/msvcsink.cpp | 80 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 80 insertions(+)
 create mode 100644 src/zencore/logging/msvcsink.cpp

(limited to 'src/zencore/logging/msvcsink.cpp')

diff --git a/src/zencore/logging/msvcsink.cpp b/src/zencore/logging/msvcsink.cpp
new file mode 100644
index 000000000..457a4d6e1
--- /dev/null
+++ b/src/zencore/logging/msvcsink.cpp
@@ -0,0 +1,80 @@
+// Copyright Epic Games, Inc. All Rights Reserved.
+
+#include <zencore/zencore.h>
+
+#if ZEN_PLATFORM_WINDOWS
+
+#	include <zencore/logging/helpers.h>
+#	include <zencore/logging/messageonlyformatter.h>
+#	include <zencore/logging/msvcsink.h>
+
+ZEN_THIRD_PARTY_INCLUDES_START
+#	include <Windows.h>
+ZEN_THIRD_PARTY_INCLUDES_END
+
+namespace zen::logging {
+
+// Default formatter for MSVC debug output: [level] message\n
+// For error/critical messages with source info, prepends file(line): so that
+// the message is clickable in the Visual Studio Output window.
+class DefaultMsvcFormatter : public Formatter
+{
+public:
+	void Format(const LogMessage& Msg, MemoryBuffer& Dest) override
+	{
+		const auto& Source = Msg.GetSource();
+		if (Msg.GetLevel() >= LogLevel::Err && Source)
+		{
+			helpers::AppendStringView(Source.Filename, Dest);
+			Dest.push_back('(');
+			helpers::AppendInt(Source.Line, Dest);
+			Dest.push_back(')');
+			Dest.push_back(':');
+			Dest.push_back(' ');
+		}
+
+		Dest.push_back('[');
+		helpers::AppendStringView(helpers::LevelToShortString(Msg.GetLevel()), Dest);
+		Dest.push_back(']');
+		Dest.push_back(' ');
+		helpers::AppendStringView(Msg.GetPayload(), Dest);
+		Dest.push_back('\n');
+	}
+
+	std::unique_ptr<Formatter> Clone() const override { return std::make_unique<DefaultMsvcFormatter>(); }
+};
+
+MsvcSink::MsvcSink() : m_Formatter(std::make_unique<DefaultMsvcFormatter>())
+{
+}
+
+void
+MsvcSink::Log(const LogMessage& Msg)
+{
+	std::lock_guard<std::mutex> Lock(m_Mutex);
+
+	MemoryBuffer Formatted;
+	m_Formatter->Format(Msg, Formatted);
+
+	// Null-terminate for OutputDebugStringA
+	Formatted.push_back('\0');
+
+	OutputDebugStringA(Formatted.data());
+}
+
+void
+MsvcSink::Flush()
+{
+	// Nothing to flush for OutputDebugString
+}
+
+void
+MsvcSink::SetFormatter(std::unique_ptr<Formatter> InFormatter)
+{
+	std::lock_guard<std::mutex> Lock(m_Mutex);
+	m_Formatter = std::move(InFormatter);
+}
+
+}  // namespace zen::logging
+
+#endif	// ZEN_PLATFORM_WINDOWS
-- 
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