Add new thread-safe error logging API

include/SFML/System/Err.hpp

@@ -40,6 +40,12 @@ namespace sf
 ////////////////////////////////////////////////////////////
 [[nodiscard]] SFML_SYSTEM_API std::ostream& err();
 
+////////////////////////////////////////////////////////////
+/// \brief Specify buffer to which warnings and errors are logged
+///
+////////////////////////////////////////////////////////////
+SFML_SYSTEM_API void setErrorBuffer(std::streambuf* streamBuffer);
+
 } // namespace sf
 
 

src/SFML/System/CMakeLists.txt

@@ -12,6 +12,7 @@ set(SRC
     ${INCROOT}/Err.hpp
     ${INCROOT}/Export.hpp
     ${INCROOT}/InputStream.hpp
+    ${SRCROOT}/Logging.hpp
     ${INCROOT}/NativeActivity.hpp
     ${SRCROOT}/Sleep.cpp
     ${INCROOT}/Sleep.hpp

src/SFML/System/Err.cpp

@@ -26,8 +26,10 @@
 // Headers
 ////////////////////////////////////////////////////////////
 #include <SFML/System/Err.hpp>
+#include <SFML/System/Logging.hpp>
 
 #include <iostream>
+#include <mutex>
 #include <streambuf>
 
 #include <cstdio>
@@ -96,6 +98,25 @@ private:
 
 namespace sf
 {
+namespace priv
+{
+////////////////////////////////////////////////////////////
+std::mutex& errorStreamMutex()
+{
+    static std::mutex mutex;
+    return mutex;
+}
+
+
+////////////////////////////////////////////////////////////
+std::ostream& errorStream()
+{
+    static std::ostream errorStream(std::cerr.rdbuf());
+    return errorStream;
+}
+} // namespace priv
+
+
 ////////////////////////////////////////////////////////////
 std::ostream& err()
 {
@@ -106,4 +127,12 @@ std::ostream& err()
 }
 
 
+////////////////////////////////////////////////////////////
+void setErrorBuffer(std::streambuf* streamBuffer)
+{
+    const std::lock_guard lock(priv::errorStreamMutex());
+    priv::errorStream().rdbuf(streamBuffer);
+}
+
+
 } // namespace sf

src/SFML/System/Logging.hpp

@@ -0,0 +1,62 @@
+////////////////////////////////////////////////////////////
+//
+// SFML - Simple and Fast Multimedia Library
+// Copyright (C) 2007-2024 Laurent Gomila (laurent@sfml-dev.org)
+//
+// This software is provided 'as-is', without any express or implied warranty.
+// In no event will the authors be held liable for any damages arising from the use of this software.
+//
+// Permission is granted to anyone to use this software for any purpose,
+// including commercial applications, and to alter it and redistribute it freely,
+// subject to the following restrictions:
+//
+// 1. The origin of this software must not be misrepresented;
+//    you must not claim that you wrote the original software.
+//    If you use this software in a product, an acknowledgment
+//    in the product documentation would be appreciated but is not required.
+//
+// 2. Altered source versions must be plainly marked as such,
+//    and must not be misrepresented as being the original software.
+//
+// 3. This notice may not be removed or altered from any source distribution.
+//
+////////////////////////////////////////////////////////////
+
+#pragma once
+
+////////////////////////////////////////////////////////////
+// Headers
+////////////////////////////////////////////////////////////
+#include <SFML/System/Export.hpp>
+
+#include <mutex>
+#include <ostream>
+
+
+namespace sf::priv
+{
+////////////////////////////////////////////////////////////
+/// \brief Get mutex for locking error stream
+///
+////////////////////////////////////////////////////////////
+SFML_SYSTEM_API std::mutex& errorStreamMutex();
+
+////////////////////////////////////////////////////////////
+/// \brief Get error stream
+///
+////////////////////////////////////////////////////////////
+SFML_SYSTEM_API std::ostream& errorStream();
+
+////////////////////////////////////////////////////////////
+/// \brief Log warning or error to a given stream
+///
+////////////////////////////////////////////////////////////
+template <typename... Args>
+void log(Args&&... args)
+{
+    const std::lock_guard lock(errorStreamMutex());
+    (errorStream() << ... << std::forward<Args>(args));
+    errorStream() << std::endl;
+}
+
+} // namespace sf::priv

src/SFML/Window/Context.cpp

@@ -28,7 +28,7 @@
 #include <SFML/Window/Context.hpp>
 #include <SFML/Window/GlContext.hpp>
 
-#include <SFML/System/Err.hpp>
+#include <SFML/System/Logging.hpp>
 
 #include <ostream>
 #include <utility>
@@ -50,7 +50,7 @@ namespace sf
 Context::Context() : m_context(priv::GlContext::create())
 {
     if (!setActive(true))
-        err() << "Failed to set context as active during construction" << std::endl;
+        priv::log("Failed to set context as active during construction");
 }
 
 
@@ -58,7 +58,7 @@ Context::Context() : m_context(priv::GlContext::create())
 Context::~Context()
 {
     if (m_context && !setActive(false))
-        err() << "Failed to set context as inactive during destruction" << std::endl;
+        priv::log("Failed to set context as inactive during destruction");
 }
 
 
@@ -144,7 +144,7 @@ Context::Context(const ContextSettings& settings, const Vector2u& size) :
 m_context(priv::GlContext::create(settings, size))
 {
     if (!setActive(true))
-        err() << "Failed to set context as active during construction" << std::endl;
+        priv::log("Failed to set context as active during construction");
 }
 
 } // namespace sf

src/SFML/Window/Cursor.cpp

@@ -28,7 +28,7 @@
 #include <SFML/Window/Cursor.hpp>
 #include <SFML/Window/CursorImpl.hpp>
 
-#include <SFML/System/Err.hpp>
+#include <SFML/System/Logging.hpp>
 #include <SFML/System/Vector2.hpp>
 
 #include <memory>
@@ -60,7 +60,7 @@ std::optional<Cursor> Cursor::loadFromPixels(const std::uint8_t* pixels, Vector2
 {
     if ((pixels == nullptr) || (size.x == 0) || (size.y == 0))
     {
-        err() << "Failed to load cursor from pixels (invalid arguments)" << std::endl;
+        priv::log("Failed to load cursor from pixels (invalid arguments)");
         return std::nullopt;
     }
 

src/SFML/Window/EGLCheck.cpp

@@ -28,7 +28,7 @@
 ////////////////////////////////////////////////////////////
 #include <SFML/Window/EGLCheck.hpp>
 
-#include <SFML/System/Err.hpp>
+#include <SFML/System/Logging.hpp>
 
 #include <glad/egl.h>
 
@@ -163,9 +163,17 @@ void eglCheckError(const std::filesystem::path& file, unsigned int line, std::st
         }
 
         // Log the error
-        err() << "An internal EGL call failed in " << file.filename() << " (" << line << ") : "
-              << "\nExpression:\n   " << expression << "\nError description:\n   " << error << "\n   " << description << '\n'
-              << std::endl;
+        priv::log("An internal EGL call failed in ",
+                  file.filename(),
+                  " (",
+                  line,
+                  ") : ",
+                  "\nExpression:\n   ",
+                  expression,
+                  "\nError description:\n   ",
+                  error,
+                  "\n   ",
+                  description);
     }
 }
 

src/SFML/Window/EglContext.cpp

@@ -29,7 +29,7 @@
 #include <SFML/Window/EglContext.hpp>
 #include <SFML/Window/WindowImpl.hpp>
 
-#include <SFML/System/Err.hpp>
+#include <SFML/System/Logging.hpp>
 #include <SFML/System/Sleep.hpp>
 
 #include <memory>
@@ -93,7 +93,7 @@ void ensureInit()
                        {
                            // At this point, the failure is unrecoverable
                            // Dump a message to the console and let the application terminate
-                           sf::err() << "Failed to load EGL entry points" << std::endl;
+                           sf::priv::log("Failed to load EGL entry points");
 
                            assert(false);
 
@@ -177,9 +177,9 @@ EglContext::EglContext(EglContext* /*shared*/, const ContextSettings& /*settings
 {
     EglContextImpl::ensureInit();
 
-    sf::err() << "Warning: context has not been initialized. The constructor EglContext(shared, settings, size) is "
-                 "currently not implemented."
-              << std::endl;
+    sf::priv::log(
+        "Warning: context has not been initialized. The constructor EglContext(shared, settings, size) is "
+        "currently not implemented.");
 }
 
 
@@ -424,7 +424,7 @@ XVisualInfo EglContext::selectBestVisual(::Display* xDisplay, unsigned int bitsP
     if (nativeVisualId == 0)
     {
         // Should never happen...
-        err() << "No EGL visual found. You should check your graphics driver" << std::endl;
+        priv::log("No EGL visual found. You should check your graphics driver");
 
         return {};
     }
@@ -439,7 +439,7 @@ XVisualInfo EglContext::selectBestVisual(::Display* xDisplay, unsigned int bitsP
     if (visualCount == 0)
     {
         // Can't happen...
-        err() << "No X11 visual found. Bug in your EGL implementation ?" << std::endl;
+        priv::log("No X11 visual found. Bug in your EGL implementation ?");
 
         return {};
     }

src/SFML/Window/GlContext.cpp

@@ -29,7 +29,7 @@
 #include <SFML/Window/ContextSettings.hpp>
 #include <SFML/Window/GlContext.hpp>
 
-#include <SFML/System/Err.hpp>
+#include <SFML/System/Logging.hpp>
 
 #include <glad/gl.h>
 
@@ -897,7 +897,7 @@ void GlContext::initialize(const ContextSettings& requestedSettings)
 
     if (!glGetIntegervFunc || !glGetErrorFunc || !glGetStringFunc || !glEnableFunc || !glIsEnabledFunc)
     {
-        err() << "Could not load necessary function to initialize OpenGL context" << std::endl;
+        log("Could not load necessary function to initialize OpenGL context");
         return;
     }
 
@@ -949,13 +949,12 @@ void GlContext::initialize(const ContextSettings& requestedSettings)
                 !parseVersionString(version, "OpenGL ES ", m_settings.majorVersion, m_settings.minorVersion) &&
                 !parseVersionString(version, "", m_settings.majorVersion, m_settings.minorVersion))
             {
-                err() << "Unable to parse OpenGL version string: " << std::quoted(version) << ", defaulting to 1.1"
-                      << std::endl;
+                log("Unable to parse OpenGL version string: ", std::quoted(version), ", defaulting to 1.1");
             }
         }
         else
         {
-            err() << "Unable to retrieve OpenGL version string, defaulting to 1.1" << std::endl;
+            log("Unable to retrieve OpenGL version string, defaulting to 1.1");
         }
     }
 
@@ -1038,7 +1037,7 @@ void GlContext::initialize(const ContextSettings& requestedSettings)
         // Check to see if the enable was successful
         if (glIsEnabledFunc(GL_FRAMEBUFFER_SRGB) == GL_FALSE)
         {
-            err() << "Warning: Failed to enable GL_FRAMEBUFFER_SRGB" << std::endl;
+            log("Warning: Failed to enable GL_FRAMEBUFFER_SRGB");
             m_settings.sRgbCapable = false;
         }
     }
@@ -1061,19 +1060,44 @@ void GlContext::checkSettings(const ContextSettings& requestedSettings) const
         (m_settings.antialiasingLevel < requestedSettings.antialiasingLevel) ||
         (m_settings.depthBits < requestedSettings.depthBits) || (!m_settings.sRgbCapable && requestedSettings.sRgbCapable))
     {
-        err() << "Warning: The created OpenGL context does not fully meet the settings that were requested" << '\n'
-              << "Requested: version = " << requestedSettings.majorVersion << "." << requestedSettings.minorVersion
-              << " ; depth bits = " << requestedSettings.depthBits << " ; stencil bits = " << requestedSettings.stencilBits
-              << " ; AA level = " << requestedSettings.antialiasingLevel << std::boolalpha
-              << " ; core = " << ((requestedSettings.attributeFlags & ContextSettings::Core) != 0)
-              << " ; debug = " << ((requestedSettings.attributeFlags & ContextSettings::Debug) != 0)
-              << " ; sRGB = " << requestedSettings.sRgbCapable << std::noboolalpha << '\n'
-              << "Created: version = " << m_settings.majorVersion << "." << m_settings.minorVersion
-              << " ; depth bits = " << m_settings.depthBits << " ; stencil bits = " << m_settings.stencilBits
-              << " ; AA level = " << m_settings.antialiasingLevel << std::boolalpha
-              << " ; core = " << ((m_settings.attributeFlags & ContextSettings::Core) != 0)
-              << " ; debug = " << ((m_settings.attributeFlags & ContextSettings::Debug) != 0)
-              << " ; sRGB = " << m_settings.sRgbCapable << std::noboolalpha << std::endl;
+        log("Warning: The created OpenGL context does not fully meet the settings that were requested\n",
+            "Requested: version = ",
+            requestedSettings.majorVersion,
+            ".",
+            requestedSettings.minorVersion,
+            " ; depth bits = ",
+            requestedSettings.depthBits,
+            " ; stencil bits = ",
+            requestedSettings.stencilBits,
+            " ; AA level = ",
+            requestedSettings.antialiasingLevel,
+            std::boolalpha,
+            " ; core = ",
+            ((requestedSettings.attributeFlags & ContextSettings::Core) != 0),
+            " ; debug = ",
+            ((requestedSettings.attributeFlags & ContextSettings::Debug) != 0),
+            " ; sRGB = ",
+            requestedSettings.sRgbCapable,
+            std::noboolalpha,
+            '\n',
+            "Created: version = ",
+            m_settings.majorVersion,
+            ".",
+            m_settings.minorVersion,
+            " ; depth bits = ",
+            m_settings.depthBits,
+            " ; stencil bits = ",
+            m_settings.stencilBits,
+            " ; AA level = ",
+            m_settings.antialiasingLevel,
+            std::boolalpha,
+            " ; core = ",
+            ((m_settings.attributeFlags & ContextSettings::Core) != 0),
+            " ; debug = ",
+            ((m_settings.attributeFlags & ContextSettings::Debug) != 0),
+            " ; sRGB = ",
+            m_settings.sRgbCapable,
+            std::noboolalpha);
     }
 }
 

src/SFML/Window/SensorManager.cpp

@@ -27,7 +27,7 @@
 ////////////////////////////////////////////////////////////
 #include <SFML/Window/SensorManager.hpp>
 
-#include <SFML/System/Err.hpp>
+#include <SFML/System/Logging.hpp>
 
 #include <ostream>
 
@@ -59,8 +59,7 @@ void SensorManager::setEnabled(Sensor::Type sensor, bool enabled)
     }
     else
     {
-        err() << "Warning: trying to enable a sensor that is not available (call Sensor::isAvailable to check it)"
-              << std::endl;
+        log("Warning: trying to enable a sensor that is not available (call Sensor::isAvailable to check it)");
     }
 }
 
@@ -115,7 +114,7 @@ SensorManager::SensorManager()
             else
             {
                 m_sensors[sensor].available = false;
-                err() << "Warning: sensor " << i << " failed to open, will not be available" << std::endl;
+                log("Warning: sensor ", i, " failed to open, will not be available");
             }
         }
     }

src/SFML/Window/Window.cpp

@@ -29,7 +29,7 @@
 #include <SFML/Window/Window.hpp>
 #include <SFML/Window/WindowImpl.hpp>
 
-#include <SFML/System/Err.hpp>
+#include <SFML/System/Logging.hpp>
 #include <SFML/System/Sleep.hpp>
 
 #include <ostream>
@@ -164,7 +164,7 @@ bool Window::setActive(bool active) const
             return true;
         }
 
-        err() << "Failed to activate the window's context" << std::endl;
+        priv::log("Failed to activate the window's context");
         return false;
     }
 
@@ -201,7 +201,7 @@ void Window::initialize()
     // Activate the window
     if (!setActive())
     {
-        err() << "Failed to set window as active during initialization" << std::endl;
+        priv::log("Failed to set window as active during initialization");
     }
 
     WindowBase::initialize();

src/SFML/Window/WindowImpl.cpp

@@ -31,7 +31,7 @@
 #include <SFML/Window/SensorManager.hpp>
 #include <SFML/Window/WindowImpl.hpp>
 
-#include <SFML/System/Err.hpp>
+#include <SFML/System/Logging.hpp>
 #include <SFML/System/Sleep.hpp>
 #include <SFML/System/Time.hpp>
 
@@ -126,17 +126,22 @@ std::unique_ptr<WindowImpl> WindowImpl::create(
         // Make sure there's not already a fullscreen window (only one is allowed)
         if (WindowImplImpl::fullscreenWindow != nullptr)
         {
-            err() << "Creating two fullscreen windows is not allowed, switching to windowed mode" << std::endl;
+            log("Creating two fullscreen windows is not allowed, switching to windowed mode");
             state = State::Windowed;
         }
         // Make sure that the chosen video mode is compatible
         else if (!mode.isValid())
         {
-            err() << "The requested video mode is not available, switching to a valid mode" << std::endl;
+            log("The requested video mode is not available, switching to a valid mode");
             assert(!VideoMode::getFullscreenModes().empty() && "No video modes available");
             mode = VideoMode::getFullscreenModes()[0];
-            err() << "  VideoMode: { size: { " << mode.size.x << ", " << mode.size.y
-                  << " }, bitsPerPixel: " << mode.bitsPerPixel << " }" << std::endl;
+            log("  VideoMode: { size: { ",
+                mode.size.x,
+                ", ",
+                mode.size.y,
+                " }, bitsPerPixel: ",
+                mode.bitsPerPixel,
+                " }");
         }
     }
 

test/CMakeLists.txt

@@ -54,7 +54,6 @@ set(SYSTEM_SRC
     System/Angle.test.cpp
     System/Clock.test.cpp
     System/Config.test.cpp
-    System/Err.test.cpp
     System/FileInputStream.test.cpp
     System/MemoryInputStream.test.cpp
     System/Sleep.test.cpp
@@ -76,6 +75,7 @@ set(WINDOW_SRC
     Window/Context.test.cpp
     Window/ContextSettings.test.cpp
     Window/Cursor.test.cpp
+    Window/Err.test.cpp # Tested alongside Window module because the System module performs no logging
     Window/Event.test.cpp
     Window/GlResource.test.cpp
     Window/Joystick.test.cpp

test/Window/Err.test.cpp

@@ -1,8 +1,13 @@
 #include <SFML/System/Err.hpp>
 
+// Other 1st party headers
+#include <SFML/Window/Cursor.hpp>
+
 #include <catch2/catch_test_macros.hpp>
 
+#include <array>
 #include <sstream>
+#include <thread>
 
 TEST_CASE("[System] sf::err")
 {
@@ -38,4 +43,26 @@ TEST_CASE("[System] sf::err")
         sf::err().rdbuf(defaultStreamBuffer);
         CHECK(sf::err().rdbuf() == defaultStreamBuffer);
     }
+
+    SECTION("Log errors")
+    {
+        using namespace std::string_literals;
+        using namespace std::string_view_literals;
+
+        const std::stringstream stream;
+        sf::setErrorBuffer(stream.rdbuf());
+
+        // Produce logs concurrently from multiple threads
+        std::array threads{std::thread([] { (void)sf::Cursor::loadFromPixels(nullptr, {}, {}); }),
+                           std::thread([] { (void)sf::Cursor::loadFromPixels(nullptr, {}, {}); }),
+                           std::thread([] { (void)sf::Cursor::loadFromPixels(nullptr, {}, {}); })};
+        for (auto& thread : threads)
+            thread.join();
+
+        // Ensure all messages come through in their entirety without being interleaved
+        CHECK(stream.str() ==
+              "Failed to load cursor from pixels (invalid arguments)\n"
+              "Failed to load cursor from pixels (invalid arguments)\n"
+              "Failed to load cursor from pixels (invalid arguments)\n");
+    }
 }