Merge pull request #972 from mapbox/log_cleanup

Refactoring of the log system

20 files changed, 199 insertions, 347 deletions

diff --git a/android/cpp/jni.cpp b/android/cpp/jni.cpp
index 8a67c0e876..9cde5d385d 100644
--- a/android/cpp/jni.cpp
+++ b/android/cpp/jni.cpp
@@ -15,7 +15,6 @@
 #include <mbgl/android/jni.hpp>
 #include <mbgl/android/native_map_view.hpp>
 #include <mbgl/map/map.hpp>
-#include <mbgl/platform/android/log_android.hpp>
 #include <mbgl/platform/event.hpp>
 #include <mbgl/platform/log.hpp>
 #include <mbgl/storage/network_status.hpp>
@@ -806,8 +805,6 @@ jobject JNICALL nativeLatLngForPixel(JNIEnv *env, jobject obj, jlong nativeMapVi
 extern "C" {
 
 extern "C" JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM *vm, void *reserved) {
-    mbgl::Log::Set<mbgl::AndroidLogBackend>();
-
     mbgl::Log::Debug(mbgl::Event::JNI, "JNI_OnLoad");
 
     JNIEnv *env = nullptr;
diff --git a/bin/render.cpp b/bin/render.cpp
index 71981b9d96..01f6929092 100644
--- a/bin/render.cpp
+++ b/bin/render.cpp
@@ -5,15 +5,10 @@
 
 #include <mbgl/platform/default/headless_view.hpp>
 #include <mbgl/platform/default/headless_display.hpp>
+#include <mbgl/platform/log.hpp>
 #include <mbgl/storage/default_file_source.hpp>
 #include <mbgl/storage/default/sqlite_cache.hpp>
 
-#if __APPLE__
-#include <mbgl/platform/darwin/log_nslog.hpp>
-#else
-#include <mbgl/platform/default/log_stderr.hpp>
-#endif
-
 #pragma GCC diagnostic push
 #ifndef __clang__
 #pragma GCC diagnostic ignored "-Wunused-local-typedefs"
@@ -71,13 +66,6 @@ int main(int argc, char *argv[]) {
 
     using namespace mbgl;
 
-
-#if __APPLE__
-    Log::Set<NSLogBackend>();
-#else
-    Log::Set<StderrLogBackend>();
-#endif
-
     mbgl::SQLiteCache cache(cache_file);
     mbgl::DefaultFileSource fileSource(&cache);
 
diff --git a/include/mbgl/platform/android/log_android.hpp b/include/mbgl/platform/android/log_android.hpp
deleted file mode 100644
index 94d90a9b36..0000000000
--- a/include/mbgl/platform/android/log_android.hpp
+++ /dev/null
@@ -1,24 +0,0 @@
-#ifndef MBGL_PLATFORM_ANDROID_LOG_ANDROID
-#define MBGL_PLATFORM_ANDROID_LOG_ANDROID
-
-#include <mbgl/platform/log.hpp>
-
-namespace mbgl {
-
-class AndroidLogBackend : public LogBackend {
-private:
-    int severityToPriority(EventSeverity severity);
-
-public:
-    inline ~AndroidLogBackend() = default;
-
-    void record(EventSeverity severity, Event event, const std::string &msg);
-    void record(EventSeverity severity, Event event, const char* format, ...);
-    void record(EventSeverity severity, Event event, int64_t code);
-    void record(EventSeverity severity, Event event, int64_t code, const std::string &msg);
-};
-
-
-}
-
-#endif
diff --git a/include/mbgl/platform/darwin/log_nslog.hpp b/include/mbgl/platform/darwin/log_nslog.hpp
deleted file mode 100644
index d40f963036..0000000000
--- a/include/mbgl/platform/darwin/log_nslog.hpp
+++ /dev/null
@@ -1,21 +0,0 @@
-#ifndef MBGL_COMMON_NSLOG_LOG
-#define MBGL_COMMON_NSLOG_LOG
-
-#include <mbgl/platform/log.hpp>
-
-namespace mbgl {
-
-class NSLogBackend : public LogBackend {
-public:
-    inline ~NSLogBackend() = default;
-
-    void record(EventSeverity severity, Event event, const std::string &msg);
-    void record(EventSeverity severity, Event event, const char* format, ...);
-    void record(EventSeverity severity, Event event, int64_t code);
-    void record(EventSeverity severity, Event event, int64_t code, const std::string &msg);
-};
-
-
-}
-
-#endif
diff --git a/include/mbgl/platform/default/log_stderr.hpp b/include/mbgl/platform/default/log_stderr.hpp
deleted file mode 100644
index 45f76f0d1a..0000000000
--- a/include/mbgl/platform/default/log_stderr.hpp
+++ /dev/null
@@ -1,21 +0,0 @@
-#ifndef MBGL_COMMON_STDERR_LOG
-#define MBGL_COMMON_STDERR_LOG
-
-#include <mbgl/platform/log.hpp>
-
-namespace mbgl {
-
-class StderrLogBackend : public LogBackend {
-public:
-    inline ~StderrLogBackend() = default;
-
-    void record(EventSeverity severity, Event event, const std::string &msg);
-    void record(EventSeverity severity, Event event, const char* format, ...);
-    void record(EventSeverity severity, Event event, int64_t code);
-    void record(EventSeverity severity, Event event, int64_t code, const std::string &msg);
-};
-
-
-}
-
-#endif
diff --git a/include/mbgl/platform/log.hpp b/include/mbgl/platform/log.hpp
index 8b58921bbe..de7f131714 100644
--- a/include/mbgl/platform/log.hpp
+++ b/include/mbgl/platform/log.hpp
@@ -10,16 +10,19 @@
 
 namespace mbgl {
 
-class LogBackend {
+class Log {
 public:
-    virtual inline ~LogBackend() = default;
-    virtual void record(EventSeverity severity, Event event, const std::string &msg) = 0;
-    virtual void record(EventSeverity severity, Event event, const char* format, ...) = 0;
-    virtual void record(EventSeverity severity, Event event, int64_t code) = 0;
-    virtual void record(EventSeverity severity, Event event, int64_t code, const std::string &msg) = 0;
-};
+    class Observer {
+    public:
+        virtual ~Observer() = default;
+
+        // When an observer is set, this function will be called for every log
+        // message. Returning true will consume the message.
+        virtual bool onRecord(EventSeverity severity, Event event, int64_t code, const std::string &msg) = 0;
+    };
+
+    static void setObserver(std::unique_ptr<Observer> Observer);
 
-class Log {
 private:
     template <typename T, size_t N>
     constexpr static bool includes(const T e, const T (&l)[N], const size_t i = 0) {
@@ -52,20 +55,20 @@ public:
         if (!includes(severity, disabledEventSeverities) &&
             !includes(event, disabledEvents) &&
             !includes({ severity, event }, disabledEventPermutations)) {
-            if (Backend) {
-                Backend->record(severity, event, ::std::forward<Args>(args)...);
-            }
+                record(severity, event, ::std::forward<Args>(args)...);
         }
     }
 
-    template<typename T, typename ...Args>
-    static inline const T &Set(Args&& ...args) {
-        Backend = util::make_unique<T>(::std::forward<Args>(args)...);
-        return *reinterpret_cast<T *>(Backend.get());
-    }
-
 private:
-    static std::unique_ptr<LogBackend> Backend;
+    static void record(EventSeverity severity, Event event, const std::string &msg);
+    static void record(EventSeverity severity, Event event, const char* format, ...);
+    static void record(EventSeverity severity, Event event, int64_t code);
+    static void record(EventSeverity severity, Event event, int64_t code, const std::string &msg);
+
+    // This method is the data sink that must be implemented by each platform we
+    // support. It should ideally output the error message in a human readable
+    // format to the developer.
+    static void platformRecord(EventSeverity severity, Event event, int64_t code, const std::string &msg);
 };
 
 }
diff --git a/linux/main.cpp b/linux/main.cpp
index 6688905ea9..6a2be43d7c 100644
--- a/linux/main.cpp
+++ b/linux/main.cpp
@@ -1,9 +1,9 @@
 #include <mbgl/mbgl.hpp>
 #include <mbgl/util/uv.hpp>
+#include <mbgl/platform/log.hpp>
 #include <mbgl/platform/platform.hpp>
 #include <mbgl/platform/default/settings_json.hpp>
 #include <mbgl/platform/default/glfw_view.hpp>
-#include <mbgl/platform/default/log_stderr.hpp>
 #include <mbgl/storage/default_file_source.hpp>
 #include <mbgl/storage/default/sqlite_cache.hpp>
 
@@ -26,8 +26,6 @@ void quit_handler(int) {
 }
 
 int main(int argc, char *argv[]) {
-    mbgl::Log::Set<mbgl::StderrLogBackend>();
-
     int fullscreen_flag = 0;
     std::string style;
 
diff --git a/macosx/main.mm b/macosx/main.mm
index f59fbda6a8..087544f7c4 100644
--- a/macosx/main.mm
+++ b/macosx/main.mm
@@ -1,6 +1,6 @@
+#include <mbgl/platform/log.hpp>
 #include <mbgl/platform/platform.hpp>
 #include <mbgl/platform/darwin/settings_nsuserdefaults.hpp>
-#include <mbgl/platform/darwin/log_nslog.hpp>
 #include <mbgl/platform/darwin/Reachability.h>
 #include <mbgl/platform/default/glfw_view.hpp>
 #include <mbgl/storage/default_file_source.hpp>
@@ -101,8 +101,6 @@ const std::string &defaultCacheDatabase() {
 }
 
 int main() {
-    mbgl::Log::Set<mbgl::NSLogBackend>();
-
     GLFWView view;
 
     mbgl::SQLiteCache cache(defaultCacheDatabase());
diff --git a/platform/android/log_android.cpp b/platform/android/log_android.cpp
index 5e40ce33bd..9de8232bac 100644
--- a/platform/android/log_android.cpp
+++ b/platform/android/log_android.cpp
@@ -1,7 +1,5 @@
-#include <mbgl/platform/android/log_android.hpp>
+#include <mbgl/platform/log.hpp>
 
-#include <iostream>
-#include <cstdarg>
 #define __STDC_FORMAT_MACROS // NDK bug workaround: https://code.google.com/p/android/issues/detail?id=72349
 #include <cinttypes>
 
@@ -9,7 +7,9 @@
 
 namespace mbgl {
 
-int AndroidLogBackend::severityToPriority(EventSeverity severity) {
+namespace {
+
+int severityToPriority(EventSeverity severity) {
     switch(severity) {
     case EventSeverity::Debug:
         return ANDROID_LOG_DEBUG;
@@ -28,31 +28,9 @@ int AndroidLogBackend::severityToPriority(EventSeverity severity) {
     }
 }
 
-void AndroidLogBackend::record(EventSeverity severity, Event event, const std::string &msg) {
-    __android_log_print(severityToPriority(severity), EventClass(event).c_str(), "%s", msg.c_str());
-}
-
-void AndroidLogBackend::record(EventSeverity severity, Event event, const char* format, ...) {
-    va_list args;
-    va_start(args, format);
-
-    const int len = vsnprintf(nullptr, 0, format, args) + 1;
-    char* buf = new char[len];
-    vsnprintf(buf, len, format, args);
-
-    va_end(args);
-
-    __android_log_print(severityToPriority(severity), EventClass(event).c_str(), "%s", buf);
-
-    delete buf;
-    buf  = nullptr;
-}
-
-void AndroidLogBackend::record(EventSeverity severity, Event event, int64_t code) {
-    __android_log_print(severityToPriority(severity), EventClass(event).c_str(), "(%" PRId64 ")", code);
-}
+} // namespace
 
-void AndroidLogBackend::record(EventSeverity severity, Event event, int64_t code, const std::string &msg) {
+void Log::platformRecord(EventSeverity severity, Event event, int64_t code, const std::string &msg) {
     __android_log_print(severityToPriority(severity), EventClass(event).c_str(), "(%" PRId64 ") %s", code, msg.c_str());
 }
 
diff --git a/platform/darwin/log_nslog.mm b/platform/darwin/log_nslog.mm
index a82d78a01f..5d53ed812f 100644
--- a/platform/darwin/log_nslog.mm
+++ b/platform/darwin/log_nslog.mm
@@ -1,37 +1,11 @@
-#include <mbgl/platform/darwin/log_nslog.hpp>
+#include <mbgl/platform/log.hpp>
 
 #import <Foundation/Foundation.h>
 
-#include <cstdarg>
-
 namespace mbgl {
 
-void NSLogBackend::record(EventSeverity severity, Event event, const std::string &msg) {
-    NSString *message =
-        [[NSString alloc] initWithBytes:msg.data() length:msg.size() encoding:NSUTF8StringEncoding];
-    NSLog(@"[%s] %s: %@", EventSeverityClass(severity).c_str(), EventClass(event).c_str(), message);
-}
-
-void NSLogBackend::record(EventSeverity severity, Event event, const char *format, ...) {
-    va_list args;
-    va_start(args, format);
-    const size_t len = vsnprintf(NULL, 0, format, args);
-    va_end(args);
-    std::unique_ptr<char[]> buffer(new char[len + 1]);
-    va_start(args, format);
-    vsnprintf(buffer.get(), len + 1, format, args);
-    va_end(args);
-    NSLog(@"[%s] %s: %s", EventSeverityClass(severity).c_str(), EventClass(event).c_str(),
-          buffer.get());
-}
-
-void NSLogBackend::record(EventSeverity severity, Event event, int64_t code) {
-    NSLog(@"[%s] %s: (%lld)", EventSeverityClass(severity).c_str(), EventClass(event).c_str(),
-          code);
-}
-
-void NSLogBackend::record(EventSeverity severity, Event event, int64_t code,
-                          const std::string &msg) {
+void Log::platformRecord(EventSeverity severity, Event event, int64_t code,
+                         const std::string &msg) {
     NSString *message =
         [[NSString alloc] initWithBytes:msg.data() length:msg.size() encoding:NSUTF8StringEncoding];
     NSLog(@"[%s] %s: (%lld) %@", EventSeverityClass(severity).c_str(), EventClass(event).c_str(),
diff --git a/platform/default/log_stderr.cpp b/platform/default/log_stderr.cpp
index 62938b6d63..3305176d96 100644
--- a/platform/default/log_stderr.cpp
+++ b/platform/default/log_stderr.cpp
@@ -1,30 +1,11 @@
-#include <mbgl/platform/default/log_stderr.hpp>
+#include <mbgl/platform/log.hpp>
 
 #include <iostream>
-#include <cstdarg>
 
 namespace mbgl {
 
-void StderrLogBackend::record(EventSeverity severity, Event event, const std::string &msg) {
-    std::cerr << "[" << severity << "] " << event << ": " << msg << std::endl;
-}
-
-void StderrLogBackend::record(EventSeverity severity, Event event, const char* format, ...) {
-    std::cerr << "[" << severity << "] " << event << ": ";
-    va_list args;
-    va_start(args, format);
-    vfprintf(stderr, format, args);
-    va_end(args);
-    std::cerr << std::endl;
-}
-
-void StderrLogBackend::record(EventSeverity severity, Event event, int64_t code) {
-    std::cerr << "[" << severity << "] " << event << ": (" << code << ")" << std::endl;
-}
-
-void StderrLogBackend::record(EventSeverity severity, Event event, int64_t code, const std::string &msg) {
+void Log::platformRecord(EventSeverity severity, Event event, int64_t code, const std::string &msg) {
     std::cerr << "[" << severity << "] " << event << ": (" << code << ") " << msg << std::endl;
-
 }
 
 }
diff --git a/platform/ios/MGLMapView.mm b/platform/ios/MGLMapView.mm
index 3629430263..57760717d9 100644
--- a/platform/ios/MGLMapView.mm
+++ b/platform/ios/MGLMapView.mm
@@ -1,6 +1,6 @@
 #import "MGLMapView.h"
 
-#import <mbgl/platform/darwin/log_nslog.hpp>
+#import <mbgl/platform/log.hpp>
 #import <mbgl/platform/gl.hpp>
 
 #import <GLKit/GLKit.h>
@@ -181,10 +181,6 @@ mbgl::DefaultFileSource *mbglFileSource = nullptr;
 
 - (BOOL)commonInit
 {
-    // set logging backend
-    //
-    mbgl::Log::Set<mbgl::NSLogBackend>();
-
     // create context
     //
     _context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
diff --git a/src/mbgl/platform/log.cpp b/src/mbgl/platform/log.cpp
index b83c7a9322..e9712f727c 100644
--- a/src/mbgl/platform/log.cpp
+++ b/src/mbgl/platform/log.cpp
@@ -1,7 +1,43 @@
 #include <mbgl/platform/log.hpp>
 
+#include <cstdarg>
+
 namespace mbgl {
 
-std::unique_ptr<LogBackend> Log::Backend;
+namespace {
+
+static std::unique_ptr<Log::Observer> currentObserver;
+
+}
+
+void Log::setObserver(std::unique_ptr<Observer> observer) {
+    currentObserver = std::move(observer);
+}
+
+void Log::record(EventSeverity severity, Event event, const std::string &msg) {
+    record(severity, event, -1, msg);
+}
+
+void Log::record(EventSeverity severity, Event event, const char* format, ...) {
+    va_list args;
+    va_start(args, format);
+    char msg[4096];
+    vsnprintf(msg, sizeof(msg), format, args);
+    va_end(args);
+
+    record(severity, event, -1, msg);
+}
+
+void Log::record(EventSeverity severity, Event event, int64_t code) {
+    record(severity, event, code, std::string());
+}
+
+void Log::record(EventSeverity severity, Event event, int64_t code, const std::string &msg) {
+    if (currentObserver && currentObserver->onRecord(severity, event, code, msg)) {
+        return;
+    }
+
+    platformRecord(severity, event, code, msg);
+}
 
 }
diff --git a/test/fixtures/fixture_log.cpp b/test/fixtures/fixture_log.cpp
deleted file mode 100644
index 02715fd43d..0000000000
--- a/test/fixtures/fixture_log.cpp
+++ /dev/null
@@ -1,96 +0,0 @@
-#include "fixture_log.hpp"
-
-namespace mbgl {
-
-FixtureLogBackend::LogMessage::LogMessage(EventSeverity severity_, Event event_, int64_t code_,
-                                          const std::string &msg_)
-    : severity(severity_), event(event_), code(code_), msg(msg_) {
-}
-FixtureLogBackend::LogMessage::LogMessage(EventSeverity severity_, Event event_, int64_t code_)
-    : severity(severity_), event(event_), code(code_), msg() {
-}
-FixtureLogBackend::LogMessage::LogMessage(EventSeverity severity_, Event event_,
-                                          const std::string &msg_)
-    : severity(severity_), event(event_), code(), msg(msg_) {
-}
-
-FixtureLogBackend::LogMessage::LogMessage(EventSeverity severity_, Event event_)
-    : severity(severity_), event(event_), code(), msg() {
-}
-
-bool FixtureLogBackend::LogMessage::operator==(const LogMessage &rhs) const {
-    return (!severity || !rhs.severity || severity.get() == rhs.severity.get()) &&
-           (!event || !rhs.event || event.get() == rhs.event.get()) &&
-           (!code || !rhs.code || code.get() == rhs.code.get()) &&
-           (!msg || !rhs.msg || msg.get() == rhs.msg.get());
-}
-
-FixtureLogBackend::~FixtureLogBackend() {
-    std::cerr << unchecked();
-}
-
-void FixtureLogBackend::record(EventSeverity severity, Event event, const std::string &msg) {
-    messages.emplace_back(severity, event, msg);
-}
-
-void FixtureLogBackend::record(EventSeverity severity, Event event, const char *format, ...) {
-    va_list args;
-    va_start(args, format);
-    const size_t len = vsnprintf(NULL, 0, format, args);
-    va_end(args);
-    std::unique_ptr<char[]> buffer(new char[len + 1]);
-    va_start(args, format);
-    vsnprintf(buffer.get(), len + 1, format, args);
-    va_end(args);
-    messages.emplace_back(severity, event, std::string{ buffer.get(), len });
-}
-
-void FixtureLogBackend::record(EventSeverity severity, Event event, int64_t code) {
-    messages.emplace_back(severity, event, code);
-}
-
-void FixtureLogBackend::record(EventSeverity severity, Event event, int64_t code,
-                               const std::string &msg) {
-    messages.emplace_back(severity, event, code, msg);
-}
-
-size_t FixtureLogBackend::count(const LogMessage &message) const {
-    size_t message_count = 0;
-    for (const LogMessage &msg : messages) {
-        if (msg == message) {
-            message_count++;
-            msg.checked = true;
-        }
-    }
-    return message_count;
-}
-
-std::vector<FixtureLogBackend::LogMessage> FixtureLogBackend::unchecked() const {
-    std::vector<LogMessage> unchecked_messages;
-    for (const LogMessage &msg : messages) {
-        if (!msg.checked) {
-            unchecked_messages.push_back(msg);
-            msg.checked = true;
-        }
-    }
-    return unchecked_messages;
-}
-
-::std::ostream &operator<<(::std::ostream &os,
-                           const std::vector<FixtureLogBackend::LogMessage> &messages) {
-    for (const FixtureLogBackend::LogMessage &message : messages) {
-        os << "- " << message;
-    }
-    return os;
-}
-
-::std::ostream &operator<<(::std::ostream &os, const FixtureLogBackend::LogMessage &message) {
-    os << "[\"" << message.severity.get() << "\", \"" << message.event.get() << "\"";
-    if (message.code)
-        os << ", " << message.code.get();
-    if (message.msg)
-        os << ", \"" << message.msg.get() << "\"";
-    return os << "]" << std::endl;
-}
-
-}
\ No newline at end of file
diff --git a/test/fixtures/fixture_log.hpp b/test/fixtures/fixture_log.hpp
deleted file mode 100644
index bc7c9fab31..0000000000
--- a/test/fixtures/fixture_log.hpp
+++ /dev/null
@@ -1,52 +0,0 @@
-#ifndef MBGL_TEST_FIXTURE_LOG
-#define MBGL_TEST_FIXTURE_LOG
-
-#include <mbgl/platform/log.hpp>
-#include <mbgl/util/noncopyable.hpp>
-#include <mbgl/util/optional.hpp>
-
-#include <vector>
-#include <cstdarg>
-#include <iostream>
-
-namespace mbgl {
-
-class FixtureLogBackend : public LogBackend, private util::noncopyable {
-public:
-    struct LogMessage {
-        LogMessage(EventSeverity severity_, Event event_, int64_t code_, const std::string &msg_);
-        LogMessage(EventSeverity severity_, Event event_, int64_t code_);
-        LogMessage(EventSeverity severity_, Event event_, const std::string &msg_);
-        LogMessage(EventSeverity severity_, Event event_);
-
-        bool operator==(const LogMessage &rhs) const;
-
-        const mapbox::util::optional<EventSeverity> severity;
-        const mapbox::util::optional<Event> event;
-        const mapbox::util::optional<int64_t> code;
-        const mapbox::util::optional<std::string> msg;
-
-        mutable bool checked = false;
-    };
-
-    ~FixtureLogBackend();
-
-    inline void record(EventSeverity severity, Event event, const std::string &msg);
-    inline void record(EventSeverity severity, Event event, const char *format, ...);
-    inline void record(EventSeverity severity, Event event, int64_t code);
-    inline void record(EventSeverity severity, Event event, int64_t code, const std::string &msg);
-
-    size_t count(const LogMessage &message) const;
-    std::vector<LogMessage> unchecked() const;
-
-public:
-    std::vector<LogMessage> messages;
-};
-
-::std::ostream &operator<<(::std::ostream &os,
-                           const std::vector<FixtureLogBackend::LogMessage> &messages);
-::std::ostream &operator<<(::std::ostream &os, const FixtureLogBackend::LogMessage &message);
-
-}
-
-#endif
diff --git a/test/fixtures/fixture_log_observer.cpp b/test/fixtures/fixture_log_observer.cpp
new file mode 100644
index 0000000000..08a6415643
--- /dev/null
+++ b/test/fixtures/fixture_log_observer.cpp
@@ -0,0 +1,68 @@
+#include "fixture_log_observer.hpp"
+#include "../fixtures/util.hpp"
+
+namespace mbgl {
+
+FixtureLogObserver::LogMessage::LogMessage(EventSeverity severity_, Event event_, int64_t code_,
+                                          const std::string &msg_)
+    : severity(severity_), event(event_), code(code_), msg(msg_) {
+}
+
+bool FixtureLogObserver::LogMessage::operator==(const LogMessage &rhs) const {
+    return (!severity || !rhs.severity || severity.get() == rhs.severity.get()) &&
+           (!event || !rhs.event || event.get() == rhs.event.get()) &&
+           (!code || !rhs.code || code.get() == rhs.code.get()) &&
+           (!msg || !rhs.msg || msg.get() == rhs.msg.get());
+}
+
+FixtureLogObserver::~FixtureLogObserver() {
+    std::cerr << unchecked();
+}
+
+bool FixtureLogObserver::onRecord(EventSeverity severity, Event event, int64_t code,
+                                  const std::string &msg) {
+    messages.emplace_back(severity, event, code, msg);
+
+    return true;
+}
+
+size_t FixtureLogObserver::count(const LogMessage &message) const {
+    size_t message_count = 0;
+    for (const LogMessage &msg : messages) {
+        if (msg == message) {
+            message_count++;
+            msg.checked = true;
+        }
+    }
+    return message_count;
+}
+
+std::vector<FixtureLogObserver::LogMessage> FixtureLogObserver::unchecked() const {
+    std::vector<LogMessage> unchecked_messages;
+    for (const LogMessage &msg : messages) {
+        if (!msg.checked) {
+            unchecked_messages.push_back(msg);
+            msg.checked = true;
+        }
+    }
+    return unchecked_messages;
+}
+
+::std::ostream &operator<<(::std::ostream &os,
+                           const std::vector<FixtureLogObserver::LogMessage> &messages) {
+    for (const FixtureLogObserver::LogMessage &message : messages) {
+        os << "- " << message;
+    }
+    return os;
+}
+
+::std::ostream &operator<<(::std::ostream &os, const FixtureLogObserver::LogMessage &message) {
+    os << "[\"" << message.severity.get() << "\", \"" << message.event.get() << "\"";
+    if (message.code)
+        os << ", " << message.code.get();
+    if (message.msg)
+        os << ", \"" << message.msg.get() << "\"";
+    return os << "]" << std::endl;
+}
+
+}
diff --git a/test/fixtures/fixture_log_observer.hpp b/test/fixtures/fixture_log_observer.hpp
new file mode 100644
index 0000000000..bdb7ea2ca3
--- /dev/null
+++ b/test/fixtures/fixture_log_observer.hpp
@@ -0,0 +1,47 @@
+#ifndef MBGL_TEST_FIXTURE_LOG_OBSERVER
+#define MBGL_TEST_FIXTURE_LOG_OBSERVER
+
+#include <mbgl/platform/log.hpp>
+#include <mbgl/util/noncopyable.hpp>
+#include <mbgl/util/optional.hpp>
+
+#include <vector>
+#include <cstdarg>
+#include <iostream>
+
+namespace mbgl {
+
+class FixtureLogObserver : public Log::Observer, private util::noncopyable {
+public:
+    struct LogMessage {
+        LogMessage(EventSeverity severity_, Event event_, int64_t code_, const std::string &msg_);
+
+        bool operator==(const LogMessage &rhs) const;
+
+        const mapbox::util::optional<EventSeverity> severity;
+        const mapbox::util::optional<Event> event;
+        const mapbox::util::optional<int64_t> code;
+        const mapbox::util::optional<std::string> msg;
+
+        mutable bool checked = false;
+    };
+
+    ~FixtureLogObserver();
+
+    // Log::Observer implementation
+    virtual bool onRecord(EventSeverity severity, Event event, int64_t code, const std::string &msg) override;
+
+    size_t count(const LogMessage &message) const;
+    std::vector<LogMessage> unchecked() const;
+
+public:
+    std::vector<LogMessage> messages;
+};
+
+::std::ostream &operator<<(::std::ostream &os,
+                           const std::vector<FixtureLogObserver::LogMessage> &messages);
+::std::ostream &operator<<(::std::ostream &os, const FixtureLogObserver::LogMessage &message);
+
+}
+
+#endif
diff --git a/test/headless/headless.cpp b/test/headless/headless.cpp
index bf04cbcb4b..c47b9349a8 100644
--- a/test/headless/headless.cpp
+++ b/test/headless/headless.cpp
@@ -1,5 +1,5 @@
 #include "../fixtures/util.hpp"
-#include "../fixtures/fixture_log.hpp"
+#include "../fixtures/fixture_log_observer.hpp"
 
 #include <mbgl/map/map.hpp>
 #include <mbgl/util/image.hpp>
@@ -101,7 +101,7 @@ TEST_P(HeadlessTest, render) {
     ASSERT_FALSE(infoDoc.HasParseError());
     ASSERT_TRUE(infoDoc.IsObject());
 
-    Log::Set<FixtureLogBackend>();
+    Log::setObserver(util::make_unique<FixtureLogObserver>());
 
     Log::Info(Event::General, "test fixture %s", base.c_str());
 
diff --git a/test/miscellaneous/style_parser.cpp b/test/miscellaneous/style_parser.cpp
index 2cb3056204..f5b9bb7e63 100644
--- a/test/miscellaneous/style_parser.cpp
+++ b/test/miscellaneous/style_parser.cpp
@@ -5,7 +5,7 @@
 
 #include <rapidjson/document.h>
 
-#include "../fixtures/fixture_log.hpp"
+#include "../fixtures/fixture_log_observer.hpp"
 
 #include <iostream>
 #include <fstream>
@@ -36,7 +36,8 @@ TEST_P(StyleParserTest, ParseStyle) {
     std::stringstream stylejson;
     stylejson << stylefile.rdbuf();
 
-    const FixtureLogBackend &log = Log::Set<FixtureLogBackend>();
+    FixtureLogObserver* observer = new FixtureLogObserver();
+    Log::setObserver(std::unique_ptr<Log::Observer>(observer));
 
     Style style;
     style.loadJSON((const uint8_t *)stylejson.str().c_str());
@@ -54,17 +55,18 @@ TEST_P(StyleParserTest, ParseStyle) {
                 ASSERT_EQ(true, js_entry.IsArray());
 
                 const uint32_t count = js_entry[rapidjson::SizeType(0)].GetUint();
-                const FixtureLogBackend::LogMessage message {
+                const FixtureLogObserver::LogMessage message {
                     EventSeverityClass(js_entry[rapidjson::SizeType(1)].GetString()),
                     EventClass(js_entry[rapidjson::SizeType(2)].GetString()),
+                    int64_t(-1),
                     js_entry[rapidjson::SizeType(3)].GetString()
                 };
 
-                EXPECT_EQ(count, log.count(message)) << "Message: " << message << std::endl;
+                EXPECT_EQ(count, observer->count(message)) << "Message: " << message << std::endl;
             }
         }
 
-        const auto &unchecked = log.unchecked();
+        const auto &unchecked = observer->unchecked();
         if (unchecked.size()) {
             std::cerr << "Unchecked Log Messages (" << base << "/" << name << "): " << std::endl << unchecked;
         }
diff --git a/test/test.gyp b/test/test.gyp
index bee2f4c4ef..9e542aec2f 100644
--- a/test/test.gyp
+++ b/test/test.gyp
@@ -32,8 +32,8 @@
         'fixtures/main.cpp',
         'fixtures/util.hpp',
         'fixtures/util.cpp',
-        'fixtures/fixture_log.hpp',
-        'fixtures/fixture_log.cpp',
+        'fixtures/fixture_log_observer.hpp',
+        'fixtures/fixture_log_observer.cpp',
 
         'headless/headless.cpp',