Do logging on a background thread

Makes logging actually thread-safe and slightly improves performance.

aegisub/libaegisub/common/log.cpp

@@ -22,6 +22,7 @@
 
 #include "libaegisub/cajun/elements.h"
 #include "libaegisub/cajun/writer.h"
+#include "libaegisub/dispatch.h"
 #include "libaegisub/io.h"
 #include "libaegisub/util.h"
 
@@ -31,6 +32,7 @@
 #include <boost/range/algorithm.hpp>
 #include <cstring>
 #include <functional>
+#include <mutex>
 
 namespace agi {
 	namespace log {
@@ -42,30 +44,45 @@ LogSink *log;
 /// Keep this ordered the same as Severity
 const char *Severity_ID = "EAWID";
 
+LogSink::LogSink()
+: messages(250)
+, queue(dispatch::Create())
+{ }
+
 LogSink::~LogSink() {
 	// The destructor for emitters may try to log messages, so disable all the
 	// emitters before destructing any
 	std::vector<Emitter*> emitters_temp;
-	swap(emitters_temp, emitters);
+	queue->Sync([&]{ swap(emitters_temp, emitters); });
 	util::delete_clear(emitters_temp);
 }
 
 void LogSink::Log(SinkMessage const& sm) {
-	messages.push_back(sm);
+	queue->Async([=]{
-	boost::for_each(emitters, [=](Emitter *em) { em->log(&messages.back()); });
+		messages.push_back(sm);
+		boost::for_each(emitters, [=](Emitter *em) { em->log(&messages.back()); });
+	});
 }
 
 void LogSink::Subscribe(Emitter *em) {
 	LOG_D("agi/log/emitter/subscribe") << "Subscribe: " << this;
-	emitters.push_back(em);
+	queue->Sync([=] { emitters.push_back(em); });
 }
 
 void LogSink::Unsubscribe(Emitter *em) {
-	emitters.erase(remove(emitters.begin(), emitters.end(), em), emitters.end());
+	queue->Sync([=] {
-	delete em;
+		emitters.erase(remove(emitters.begin(), emitters.end(), em), emitters.end());
+		delete em;
+	});
 	LOG_D("agi/log/emitter/unsubscribe") << "Un-Subscribe: " << this;
 }
 
+decltype(LogSink::messages) LogSink::GetMessages() const {
+	decltype(LogSink::messages) ret;
+	queue->Sync([&] { ret = messages; });
+	return ret;
+}
+
 Message::Message(const char *section, Severity severity, const char *file, const char *func, int line)
 : msg(nullptr, 1024)
 {

aegisub/libaegisub/include/libaegisub/log.h

@@ -47,6 +47,8 @@
 #define LOG_D_IF(cond, section) if (cond) LOG_SINK(section, agi::log::Debug)
 
 namespace agi {
+	namespace dispatch { class Queue; }
+
 	namespace log {
 class LogSink;
 
@@ -82,12 +84,13 @@ class Emitter;
 /// Log sink, single destination for all messages
 class LogSink {
 	boost::circular_buffer<SinkMessage> messages;
+	std::unique_ptr<dispatch::Queue> queue;
 
 	/// List of pointers to emitters
 	std::vector<Emitter*> emitters;
 
 public:
-	LogSink() : messages(250) { }
+	LogSink();
 	~LogSink();
 
 	/// Insert a message into the sink.
@@ -105,7 +108,7 @@ public:
 
 	/// @brief @get the complete (current) log.
 	/// @return Const pointer to internal sink.
-	decltype(messages) const& GetSink() const { return messages; }
+	decltype(messages) GetMessages() const;
 };
 
 /// An emitter to produce human readable output for a log sink.

aegisub/src/dialog_log.cpp

@@ -39,6 +39,7 @@
 #include "compat.h"
 #include "include/aegisub/context.h"
 
+#include <libaegisub/dispatch.h>
 #include <libaegisub/log.h>
 
 #include <algorithm>
@@ -57,7 +58,7 @@ public:
 	EmitLog(wxTextCtrl *t)
 	: text_ctrl(t)
 	{
-		for (auto sm : agi::log::log->GetSink())
+		for (auto sm : agi::log::log->GetMessages())
 			log(&sm);
 	}
 
@@ -86,7 +87,11 @@ public:
 			sm->line,
 			to_wx(sm->message));
 #endif
-		text_ctrl->AppendText(log);
+
+		if (wxIsMainThread())
+			text_ctrl->AppendText(log);
+		else
+			agi::dispatch::Main().Async([=]{ text_ctrl->AppendText(log); });
 	}
 };