Moved most variables in sfml-graphics, GlResource and GlContext out of namespace scope.

include/SFML/Window/GlResource.hpp

@@ -29,6 +29,8 @@
 ////////////////////////////////////////////////////////////
 #include <SFML/Window/Export.hpp>
 
+#include <memory>
+
 
 namespace sf
 {
@@ -48,23 +50,24 @@ protected:
     GlResource();
 
     ////////////////////////////////////////////////////////////
-    /// \brief Destructor
+    /// \brief Register an OpenGL object to be destroyed when its containing context is destroyed
-    ///
-    ////////////////////////////////////////////////////////////
-    ~GlResource();
-
-    ////////////////////////////////////////////////////////////
-    /// \brief Register a function to be called when a context is destroyed
     ///
     /// This is used for internal purposes in order to properly
     /// clean up OpenGL resources that cannot be shared between
     /// contexts.
     ///
-    /// \param callback Function to be called when a context is destroyed
+    /// \param object Object to be destroyed when its containing context is destroyed
-    /// \param arg      Argument to pass when calling the function
     ///
     ////////////////////////////////////////////////////////////
-    static void registerContextDestroyCallback(ContextDestroyCallback callback, void* arg);
+    static void registerUnsharedGlObject(std::shared_ptr<void> object);
+
+    ////////////////////////////////////////////////////////////
+    /// \brief Unregister an OpenGL object from its containing context
+    ///
+    /// \param object Object to be unregistered
+    ///
+    ////////////////////////////////////////////////////////////
+    static void unregisterUnsharedGlObject(std::shared_ptr<void> object);
 
     ////////////////////////////////////////////////////////////
     /// \brief RAII helper class to temporarily lock an available context for use
@@ -97,6 +100,12 @@ protected:
         ////////////////////////////////////////////////////////////
         TransientContextLock& operator=(const TransientContextLock&) = delete;
     };
+
+private:
+    ////////////////////////////////////////////////////////////
+    // Member data
+    ////////////////////////////////////////////////////////////
+    std::shared_ptr<void> m_sharedContext; //!< Shared context used to link all contexts together for resource sharing
 };
 
 } // namespace sf

src/SFML/Graphics/RenderTarget.cpp

@@ -54,30 +54,35 @@ namespace
 namespace RenderTargetImpl
 {
 // Mutex to protect ID generation and our context-RenderTarget-map
-std::recursive_mutex mutex;
+std::recursive_mutex& getMutex()
+{
+    static std::recursive_mutex mutex;
+    return mutex;
+}
 
 // Unique identifier, used for identifying RenderTargets when
 // tracking the currently active RenderTarget within a given context
 std::uint64_t getUniqueId()
 {
-    const std::lock_guard lock(mutex);
+    const std::lock_guard lock(getMutex());
-
+    static std::uint64_t  id = 1; // start at 1, zero is "no RenderTarget"
-    static std::uint64_t id = 1; // start at 1, zero is "no RenderTarget"
-
     return id++;
 }
 
 // Map to help us detect whether a different RenderTarget
 // has been activated within a single context
 using ContextRenderTargetMap = std::unordered_map<std::uint64_t, std::uint64_t>;
-ContextRenderTargetMap contextRenderTargetMap;
+ContextRenderTargetMap& getContextRenderTargetMap()
+{
+    static ContextRenderTargetMap contextRenderTargetMap;
+    return contextRenderTargetMap;
+}
 
 // Check if a RenderTarget with the given ID is active in the current context
 bool isActive(std::uint64_t id)
 {
-    const auto it = contextRenderTargetMap.find(sf::Context::getActiveContextId());
+    const auto it = getContextRenderTargetMap().find(sf::Context::getActiveContextId());
-
+    return (it != getContextRenderTargetMap().end()) && (it->second == id);
-    return (it != contextRenderTargetMap.end()) && (it->second == id);
 }
 
 // Convert an sf::BlendMode::Factor constant to the corresponding OpenGL constant.
@@ -393,12 +398,13 @@ bool RenderTarget::setActive(bool active)
 {
     // Mark this RenderTarget as active or no longer active in the tracking map
     {
-        const std::lock_guard lock(RenderTargetImpl::mutex);
+        const std::lock_guard lock(RenderTargetImpl::getMutex());
 
         const std::uint64_t contextId = Context::getActiveContextId();
 
-        using RenderTargetImpl::contextRenderTargetMap;
+        using RenderTargetImpl::getContextRenderTargetMap;
-        const auto it = contextRenderTargetMap.find(contextId);
+        auto& contextRenderTargetMap = getContextRenderTargetMap();
+        auto  it                     = contextRenderTargetMap.find(contextId);
 
         if (active)
         {

src/SFML/Graphics/RenderTextureImplFBO.cpp

@@ -36,98 +36,31 @@
 
 #include <mutex>
 #include <ostream>
-#include <set>
-#include <unordered_map>
-#include <unordered_set>
-#include <utility>
-
-
-namespace
-{
-// Set to track all active FBO mappings
-// This is used to free active FBOs while their owning
-// RenderTextureImplFBO is still alive
-std::unordered_set<std::unordered_map<std::uint64_t, unsigned int>*> frameBuffers;
-
-// Set to track all stale FBOs
-// This is used to free stale FBOs after their owning
-// RenderTextureImplFBO has already been destroyed
-// An FBO cannot be destroyed until it's containing context
-// becomes active, so the destruction of the RenderTextureImplFBO
-// has to be decoupled from the destruction of the FBOs themselves
-std::set<std::pair<std::uint64_t, unsigned int>> staleFrameBuffers;
-
-// Mutex to protect both active and stale frame buffer sets
-std::recursive_mutex mutex;
-
-// This function is called either when a RenderTextureImplFBO is
-// destroyed or via contextDestroyCallback when context destruction
-// might trigger deletion of its contained stale FBOs
-void destroyStaleFBOs()
-{
-    const std::uint64_t contextId = sf::Context::getActiveContextId();
-
-    for (auto it = staleFrameBuffers.begin(); it != staleFrameBuffers.end();)
-    {
-        if (it->first == contextId)
-        {
-            const auto frameBuffer = static_cast<GLuint>(it->second);
-            glCheck(GLEXT_glDeleteFramebuffers(1, &frameBuffer));
-
-            staleFrameBuffers.erase(it++);
-        }
-        else
-        {
-            ++it;
-        }
-    }
-}
-
-// Callback that is called every time a context is destroyed
-void contextDestroyCallback(void* /*arg*/)
-{
-    const std::lock_guard lock(mutex);
-
-    const std::uint64_t contextId = sf::Context::getActiveContextId();
-
-    // Destroy active frame buffer objects
-    for (auto* frameBuffer : frameBuffers)
-    {
-        for (auto it = frameBuffer->begin(); it != frameBuffer->end(); ++it)
-        {
-            if (it->first == contextId)
-            {
-                const GLuint frameBufferId = it->second;
-                glCheck(GLEXT_glDeleteFramebuffers(1, &frameBufferId));
-
-                // Erase the entry from the RenderTextureImplFBO's map
-                frameBuffer->erase(it);
-
-                break;
-            }
-        }
-    }
-
-    // Destroy stale frame buffer objects
-    destroyStaleFBOs();
-}
-} // namespace
 
 
 namespace sf::priv
 {
 ////////////////////////////////////////////////////////////
-RenderTextureImplFBO::RenderTextureImplFBO()
+struct RenderTextureImplFBO::FrameBufferObject
 {
-    const std::lock_guard lock(mutex);
+    FrameBufferObject()
+    {
+        // Create the framebuffer object
+        glCheck(GLEXT_glGenFramebuffers(1, &object));
+    }
 
-    // Register the context destruction callback
+    ~FrameBufferObject()
-    registerContextDestroyCallback(contextDestroyCallback, nullptr);
+    {
+        if (object)
+            glCheck(GLEXT_glDeleteFramebuffers(1, &object));
+    }
 
-    // Insert the new frame buffer mapping into the set of all active mappings
+    GLuint object{};
-    frameBuffers.insert(&m_frameBuffers);
+};
-    frameBuffers.insert(&m_multisampleFrameBuffers);
+
-}
+
+////////////////////////////////////////////////////////////
+RenderTextureImplFBO::RenderTextureImplFBO() = default;
 
 
 ////////////////////////////////////////////////////////////
@@ -135,12 +68,6 @@ RenderTextureImplFBO::~RenderTextureImplFBO()
 {
     const TransientContextLock contextLock;
 
-    const std::lock_guard lock(mutex);
-
-    // Remove the frame buffer mapping from the set of all active mappings
-    frameBuffers.erase(&m_frameBuffers);
-    frameBuffers.erase(&m_multisampleFrameBuffers);
-
     // Destroy the color buffer
     if (m_colorBuffer)
     {
@@ -155,15 +82,22 @@ RenderTextureImplFBO::~RenderTextureImplFBO()
         glCheck(GLEXT_glDeleteRenderbuffers(1, &depthStencilBuffer));
     }
 
-    // Move all frame buffer objects to stale set
+    // Unregister FBOs with the contexts if they haven't already been destroyed
-    for (auto& [contextId, frameBufferId] : m_frameBuffers)
+    for (auto& entry : m_frameBuffers)
-        staleFrameBuffers.emplace(contextId, frameBufferId);
+    {
+        auto frameBuffer = entry.second.lock();
 
-    for (auto& [contextId, multisampleFrameBufferId] : m_multisampleFrameBuffers)
+        if (frameBuffer)
-        staleFrameBuffers.emplace(contextId, multisampleFrameBufferId);
+            unregisterUnsharedGlObject(std::move(frameBuffer));
+    }
 
-    // Clean up FBOs
+    for (auto& entry : m_multisampleFrameBuffers)
-    destroyStaleFBOs();
+    {
+        auto frameBuffer = entry.second.lock();
+
+        if (frameBuffer)
+            unregisterUnsharedGlObject(std::move(frameBuffer));
+    }
 }
 
 
@@ -422,15 +356,14 @@ bool RenderTextureImplFBO::create(const Vector2u& size, unsigned int textureId,
 bool RenderTextureImplFBO::createFrameBuffer()
 {
     // Create the framebuffer object
-    GLuint frameBuffer = 0;
+    auto frameBuffer = std::make_shared<FrameBufferObject>();
-    glCheck(GLEXT_glGenFramebuffers(1, &frameBuffer));
 
-    if (!frameBuffer)
+    if (!frameBuffer->object)
     {
         err() << "Impossible to create render texture (failed to create the frame buffer object)" << std::endl;
         return false;
     }
-    glCheck(GLEXT_glBindFramebuffer(GLEXT_GL_FRAMEBUFFER, frameBuffer));
+    glCheck(GLEXT_glBindFramebuffer(GLEXT_GL_FRAMEBUFFER, frameBuffer->object));
 
     // Link the depth/stencil renderbuffer to the frame buffer
     if (!m_multisample && m_depthStencilBuffer)
@@ -462,33 +395,30 @@ bool RenderTextureImplFBO::createFrameBuffer()
     if (status != GLEXT_GL_FRAMEBUFFER_COMPLETE)
     {
         glCheck(GLEXT_glBindFramebuffer(GLEXT_GL_FRAMEBUFFER, 0));
-        glCheck(GLEXT_glDeleteFramebuffers(1, &frameBuffer));
         err() << "Impossible to create render texture (failed to link the target texture to the frame buffer)" << std::endl;
         return false;
     }
 
-    {
+    // Insert the FBO into our map
-        const std::lock_guard lock(mutex);
+    m_frameBuffers.emplace(Context::getActiveContextId(), frameBuffer);
 
-        // Insert the FBO into our map
+    // Register the object with the current context so it is automatically destroyed
-        m_frameBuffers.emplace(Context::getActiveContextId(), frameBuffer);
+    registerUnsharedGlObject(std::move(frameBuffer));
-    }
 
 #ifndef SFML_OPENGL_ES
 
     if (m_multisample)
     {
         // Create the multisample framebuffer object
-        GLuint multisampleFrameBuffer = 0;
+        auto multisampleFrameBuffer = std::make_shared<FrameBufferObject>();
-        glCheck(GLEXT_glGenFramebuffers(1, &multisampleFrameBuffer));
 
-        if (!multisampleFrameBuffer)
+        if (!multisampleFrameBuffer->object)
         {
             err() << "Impossible to create render texture (failed to create the multisample frame buffer object)"
                   << std::endl;
             return false;
         }
-        glCheck(GLEXT_glBindFramebuffer(GLEXT_GL_FRAMEBUFFER, multisampleFrameBuffer));
+        glCheck(GLEXT_glBindFramebuffer(GLEXT_GL_FRAMEBUFFER, multisampleFrameBuffer->object));
 
         // Link the multisample color buffer to the frame buffer
         glCheck(GLEXT_glBindRenderbuffer(GLEXT_GL_RENDERBUFFER, m_colorBuffer));
@@ -517,19 +447,17 @@ bool RenderTextureImplFBO::createFrameBuffer()
         if (status != GLEXT_GL_FRAMEBUFFER_COMPLETE)
         {
             glCheck(GLEXT_glBindFramebuffer(GLEXT_GL_FRAMEBUFFER, 0));
-            glCheck(GLEXT_glDeleteFramebuffers(1, &multisampleFrameBuffer));
             err() << "Impossible to create render texture (failed to link the render buffers to the multisample frame "
                      "buffer)"
                   << std::endl;
             return false;
         }
 
-        {
+        // Insert the FBO into our map
-            const std::lock_guard lock(mutex);
+        m_multisampleFrameBuffers.emplace(Context::getActiveContextId(), multisampleFrameBuffer);
 
-            // Insert the FBO into our map
+        // Register the object with the current context so it is automatically destroyed
-            m_multisampleFrameBuffers.emplace(Context::getActiveContextId(), multisampleFrameBuffer);
+        registerUnsharedGlObject(std::move(multisampleFrameBuffer));
-        }
     }
 
 #endif
@@ -575,29 +503,33 @@ bool RenderTextureImplFBO::activate(bool active)
     // Lookup the FBO corresponding to the currently active context
     // If none is found, there is no FBO corresponding to the
     // currently active context so we will have to create a new FBO
+    if (m_multisample)
     {
-        const std::lock_guard lock(mutex);
+        const auto it = m_multisampleFrameBuffers.find(contextId);
 
-        std::unordered_map<std::uint64_t, unsigned int>::iterator it;
+        if (it != m_multisampleFrameBuffers.end())
-
-        if (m_multisample)
         {
-            it = m_multisampleFrameBuffers.find(contextId);
+            auto frameBuffer = it->second.lock();
 
-            if (it != m_multisampleFrameBuffers.end())
+            if (frameBuffer)
             {
-                glCheck(GLEXT_glBindFramebuffer(GLEXT_GL_FRAMEBUFFER, it->second));
+                glCheck(GLEXT_glBindFramebuffer(GLEXT_GL_FRAMEBUFFER, frameBuffer->object));
 
                 return true;
             }
         }
-        else
+    }
-        {
+    else
-            it = m_frameBuffers.find(contextId);
+    {
+        const auto it = m_frameBuffers.find(contextId);
 
-            if (it != m_frameBuffers.end())
+        if (it != m_frameBuffers.end())
+        {
+            auto frameBuffer = it->second.lock();
+
+            if (frameBuffer)
             {
-                glCheck(GLEXT_glBindFramebuffer(GLEXT_GL_FRAMEBUFFER, it->second));
+                glCheck(GLEXT_glBindFramebuffer(GLEXT_GL_FRAMEBUFFER, frameBuffer->object));
 
                 return true;
             }
@@ -630,26 +562,30 @@ void RenderTextureImplFBO::updateTexture(unsigned int)
     {
         const std::uint64_t contextId = Context::getActiveContextId();
 
-        const std::lock_guard lock(mutex);
-
         const auto frameBufferIt = m_frameBuffers.find(contextId);
         const auto multisampleIt = m_multisampleFrameBuffers.find(contextId);
 
         if ((frameBufferIt != m_frameBuffers.end()) && (multisampleIt != m_multisampleFrameBuffers.end()))
         {
-            // Set up the blit target (draw framebuffer) and blit (from the read framebuffer, our multisample FBO)
+            auto frameBuffer            = frameBufferIt->second.lock();
-            glCheck(GLEXT_glBindFramebuffer(GLEXT_GL_DRAW_FRAMEBUFFER, frameBufferIt->second));
+            auto multiSampleFrameBuffer = multisampleIt->second.lock();
-            glCheck(GLEXT_glBlitFramebuffer(0,
+
-                                            0,
+            if (frameBuffer && multiSampleFrameBuffer)
-                                            static_cast<GLint>(m_size.x),
+            {
-                                            static_cast<GLint>(m_size.y),
+                // Set up the blit target (draw framebuffer) and blit (from the read framebuffer, our multisample FBO)
-                                            0,
+                glCheck(GLEXT_glBindFramebuffer(GLEXT_GL_DRAW_FRAMEBUFFER, frameBuffer->object));
-                                            0,
+                glCheck(GLEXT_glBlitFramebuffer(0,
-                                            static_cast<GLint>(m_size.x),
+                                                0,
-                                            static_cast<GLint>(m_size.y),
+                                                static_cast<GLint>(m_size.x),
-                                            GL_COLOR_BUFFER_BIT,
+                                                static_cast<GLint>(m_size.y),
-                                            GL_NEAREST));
+                                                0,
-            glCheck(GLEXT_glBindFramebuffer(GLEXT_GL_DRAW_FRAMEBUFFER, multisampleIt->second));
+                                                0,
+                                                static_cast<GLint>(m_size.x),
+                                                static_cast<GLint>(m_size.y),
+                                                GL_COLOR_BUFFER_BIT,
+                                                GL_NEAREST));
+                glCheck(GLEXT_glBindFramebuffer(GLEXT_GL_DRAW_FRAMEBUFFER, multiSampleFrameBuffer->object));
+            }
         }
     }
 

src/SFML/Graphics/RenderTextureImplFBO.hpp

@@ -137,8 +137,12 @@ private:
     ////////////////////////////////////////////////////////////
     // Member data
     ////////////////////////////////////////////////////////////
-    std::unordered_map<std::uint64_t, unsigned int> m_frameBuffers; //!< OpenGL frame buffer objects per context
+    struct FrameBufferObject;
-    std::unordered_map<std::uint64_t, unsigned int> m_multisampleFrameBuffers; //!< Optional per-context OpenGL frame buffer objects with multisample attachments
+
+    using FrameBufferObjectMap = std::unordered_map<std::uint64_t, std::weak_ptr<FrameBufferObject>>;
+
+    FrameBufferObjectMap m_frameBuffers; //!< OpenGL frame buffer objects per context
+    FrameBufferObjectMap m_multisampleFrameBuffers; //!< Optional per-context OpenGL frame buffer objects with multisample attachments
     unsigned int             m_depthStencilBuffer{}; //!< Optional depth/stencil buffer attached to the frame buffer
     unsigned int             m_colorBuffer{};        //!< Optional multisample color buffer attached to the frame buffer
     Vector2u                 m_size;                 //!< Width and height of the attachments

src/SFML/Graphics/Shader.cpp

@@ -40,7 +40,6 @@
 
 #include <fstream>
 #include <iomanip>
-#include <mutex>
 #include <ostream>
 #include <utility>
 #include <vector>
@@ -61,20 +60,17 @@
 
 namespace
 {
-std::recursive_mutex isAvailableMutex;
-
-GLint checkMaxTextureUnits()
-{
-    GLint maxUnits = 0;
-    glCheck(glGetIntegerv(GLEXT_GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS, &maxUnits));
-
-    return maxUnits;
-}
-
 // Retrieve the maximum number of texture units available
 std::size_t getMaxTextureUnits()
 {
-    static const GLint maxUnits = checkMaxTextureUnits();
+    static const GLint maxUnits = []()
+    {
+        GLint value = 0;
+        glCheck(glGetIntegerv(GLEXT_GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS, &value));
+
+        return value;
+    }();
+
     return static_cast<std::size_t>(maxUnits);
 }
 
@@ -747,23 +743,16 @@ void Shader::bind(const Shader* shader)
 ////////////////////////////////////////////////////////////
 bool Shader::isAvailable()
 {
-    const std::lock_guard lock(isAvailableMutex);
+    static const bool available = []()
-
-    static bool checked   = false;
-    static bool available = false;
-
-    if (!checked)
     {
-        checked = true;
-
         const TransientContextLock contextLock;
 
         // Make sure that extensions are initialized
         sf::priv::ensureExtensionsInit();
 
-        available = GLEXT_multitexture && GLEXT_shading_language_100 && GLEXT_shader_objects && GLEXT_vertex_shader &&
+        return GLEXT_multitexture && GLEXT_shading_language_100 && GLEXT_shader_objects && GLEXT_vertex_shader &&
-                    GLEXT_fragment_shader;
+               GLEXT_fragment_shader;
-    }
+    }();
 
     return available;
 }
@@ -772,22 +761,15 @@ bool Shader::isAvailable()
 ////////////////////////////////////////////////////////////
 bool Shader::isGeometryAvailable()
 {
-    const std::lock_guard lock(isAvailableMutex);
+    static const bool available = []()
-
-    static bool checked   = false;
-    static bool available = false;
-
-    if (!checked)
     {
-        checked = true;
-
         const TransientContextLock contextLock;
 
         // Make sure that extensions are initialized
         sf::priv::ensureExtensionsInit();
 
-        available = isAvailable() && (GLEXT_geometry_shader4 || GLEXT_GL_VERSION_3_2);
+        return isAvailable() && (GLEXT_geometry_shader4 || GLEXT_GL_VERSION_3_2);
-    }
+    }();
 
     return available;
 }

src/SFML/Graphics/Texture.cpp

@@ -71,6 +71,7 @@ Texture::Texture() : m_cacheId(TextureImpl::getUniqueId())
 
 ////////////////////////////////////////////////////////////
 Texture::Texture(const Texture& copy) :
+GlResource(copy),
 m_isSmooth(copy.m_isSmooth),
 m_sRgb(copy.m_sRgb),
 m_isRepeated(copy.m_isRepeated),

src/SFML/Graphics/VertexBuffer.cpp

@@ -84,7 +84,10 @@ VertexBuffer::VertexBuffer(PrimitiveType type, Usage usage) : m_primitiveType(ty
 
 
 ////////////////////////////////////////////////////////////
-VertexBuffer::VertexBuffer(const VertexBuffer& copy) : m_primitiveType(copy.m_primitiveType), m_usage(copy.m_usage)
+VertexBuffer::VertexBuffer(const VertexBuffer& copy) :
+GlResource(copy),
+m_primitiveType(copy.m_primitiveType),
+m_usage(copy.m_usage)
 {
     if (copy.m_buffer && copy.m_size)
     {

src/SFML/Window/GlContext.cpp

@@ -167,17 +167,6 @@ namespace
 // A nested named namespace is used here to allow unity builds of SFML.
 namespace GlContextImpl
 {
-// AMD drivers have issues with internal synchronization
-// We need to make sure that no operating system context
-// or pixel format operations are performed simultaneously
-// This mutex is also used to protect the shared context
-// from being locked on multiple threads and for managing
-// the resource count
-std::recursive_mutex mutex;
-
-// OpenGL resources counter
-unsigned int resourceCount = 0;
-
 // This structure contains all the state necessary to
 // track current context information for each thread
 struct CurrentContext
@@ -185,27 +174,156 @@ struct CurrentContext
     std::uint64_t        id{};
     sf::priv::GlContext* ptr{};
     unsigned int         transientCount{};
+
+    // This per-thread variable holds the current context information for each thread
+    static CurrentContext& get()
+    {
+        thread_local CurrentContext currentContext;
+        return currentContext;
+    }
+
+private:
+    // Private constructor to prevent CurrentContext from being constructed outside of get()
+    CurrentContext() = default;
+};
+} // namespace GlContextImpl
+} // namespace
+
+
+namespace sf::priv
+{
+// This structure contains all the state necessary to
+// track SharedContext usage
+struct GlContext::SharedContext
+{
+    ////////////////////////////////////////////////////////////
+    /// \brief Constructor
+    ///
+    ////////////////////////////////////////////////////////////
+    SharedContext()
+    {
+        const std::lock_guard lock(mutex);
+
+        context.emplace(nullptr);
+        context->initialize(sf::ContextSettings());
+
+        loadExtensions();
+
+        context->setActive(false);
+    }
+
+    ////////////////////////////////////////////////////////////
+    /// \brief Get weak_ptr
+    ///
+    /// \return weak_ptr to the SharedContext
+    ///
+    ////////////////////////////////////////////////////////////
+    static std::weak_ptr<SharedContext>& getWeakPtr()
+    {
+        static std::weak_ptr<SharedContext> weakSharedContext;
+        return weakSharedContext;
+    }
+
+    ////////////////////////////////////////////////////////////
+    /// \brief Get shared_ptr to the shared context
+    ///
+    /// Create new object if one doesn't already exist.
+    ///
+    /// \return shared_ptr to the shared context
+    ///
+    ////////////////////////////////////////////////////////////
+    static std::shared_ptr<SharedContext> get()
+    {
+        auto& weakSharedContext = getWeakPtr();
+        auto  sharedContext     = weakSharedContext.lock();
+
+        if (!sharedContext)
+        {
+            sharedContext     = std::make_shared<GlContext::SharedContext>();
+            weakSharedContext = sharedContext;
+        }
+
+        return sharedContext;
+    }
+
+    ////////////////////////////////////////////////////////////
+    /// \brief Load our extensions vector with the supported extensions
+    ///
+    ////////////////////////////////////////////////////////////
+    void loadExtensions()
+    {
+        auto glGetErrorFunc    = reinterpret_cast<glGetErrorFuncType>(getFunction("glGetError"));
+        auto glGetIntegervFunc = reinterpret_cast<glGetIntegervFuncType>(getFunction("glGetIntegerv"));
+        auto glGetStringFunc   = reinterpret_cast<glGetStringFuncType>(getFunction("glGetString"));
+
+        if (!glGetErrorFunc || !glGetIntegervFunc || !glGetStringFunc)
+            return;
+
+        // Check whether a >= 3.0 context is available
+        int majorVersion = 0;
+        glGetIntegervFunc(GL_MAJOR_VERSION, &majorVersion);
+
+        auto glGetStringiFunc = reinterpret_cast<glGetStringiFuncType>(getFunction("glGetStringi"));
+
+        if (glGetErrorFunc() == GL_INVALID_ENUM || !majorVersion || !glGetStringiFunc)
+        {
+            // Try to load the < 3.0 way
+            const char* extensionString = reinterpret_cast<const char*>(glGetStringFunc(GL_EXTENSIONS));
+
+            if (extensionString)
+            {
+                extensions.clear();
+
+                do
+                {
+                    const char* extension = extensionString;
+
+                    while (*extensionString && (*extensionString != ' '))
+                        ++extensionString;
+
+                    extensions.emplace_back(extension, extensionString);
+                } while (*extensionString++);
+            }
+        }
+        else
+        {
+            // Try to load the >= 3.0 way
+            int numExtensions = 0;
+            glGetIntegervFunc(GL_NUM_EXTENSIONS, &numExtensions);
+
+            if (numExtensions)
+            {
+                extensions.clear();
+
+                for (unsigned int i = 0; i < static_cast<unsigned int>(numExtensions); ++i)
+                {
+                    const char* extensionString = reinterpret_cast<const char*>(glGetStringiFunc(GL_EXTENSIONS, i));
+
+                    if (extensionString)
+                        extensions.emplace_back(extensionString);
+                }
+            }
+        }
+    }
+
+    // AMD drivers have issues with internal synchronization
+    // We need to make sure that no operating system context
+    // or pixel format operations are performed simultaneously
+    // This mutex is also used to protect the shared context
+    // from being locked on multiple threads
+    std::recursive_mutex mutex;
+
+    // Supported OpenGL extensions
+    std::vector<std::string> extensions;
+
+    // The hidden, inactive context that will be shared with all other contexts
+    std::optional<ContextType> context;
 };
 
-// This per-thread variable holds the current context information for each thread
-thread_local CurrentContext currentContext;
-
-// The hidden, inactive context that will be shared with all other contexts
-std::unique_ptr<ContextType> sharedContext;
-
-// Unique identifier, used for identifying contexts when managing unshareable OpenGL resources
-std::atomic<std::uint64_t> nextContextId(1); // start at 1, zero is "no context"
-
-// Set containing callback functions to be called whenever a
-// context is going to be destroyed
-// Unshareable OpenGL resources rely on this to clean up properly
-// whenever a context containing them is destroyed
-using ContextDestroyCallbacks = std::unordered_map<sf::ContextDestroyCallback, void*>;
-ContextDestroyCallbacks contextDestroyCallbacks;
 
 // This structure contains all the state necessary to
 // track TransientContext usage
-struct TransientContext
+struct GlContext::TransientContext
 {
     ////////////////////////////////////////////////////////////
     /// \brief Constructor
@@ -215,15 +333,13 @@ struct TransientContext
     {
         // TransientContext should never be created if there is
         // already a context active on the current thread
-        assert(!currentContext.id);
+        assert(!GlContextImpl::CurrentContext::get().id);
 
-        std::unique_lock lock(mutex);
+        // Lock ourselves so we don't create a new object if one doesn't already exist
+        sharedContext = SharedContext::getWeakPtr().lock();
 
-        if (resourceCount == 0)
+        if (!sharedContext)
         {
-            // No GlResources, no shared context yet
-            assert(!sharedContext);
-
             // Create a Context object for temporary use
             context.emplace();
         }
@@ -233,8 +349,8 @@ struct TransientContext
             assert(sharedContext);
 
             // Lock the shared context for temporary use
-            sharedContextLock = std::move(lock);
+            sharedContextLock = std::unique_lock(sharedContext->mutex);
-            sharedContext->setActive(true);
+            sharedContext->context->setActive(true);
         }
     }
 
@@ -245,7 +361,7 @@ struct TransientContext
     ~TransientContext()
     {
         if (sharedContextLock)
-            sharedContext->setActive(false);
+            sharedContext->context->setActive(false);
     }
 
     ////////////////////////////////////////////////////////////
@@ -260,176 +376,141 @@ struct TransientContext
     ////////////////////////////////////////////////////////////
     TransientContext& operator=(const TransientContext&) = delete;
 
+    ////////////////////////////////////////////////////////////
+    /// \brief Get the thread local TransientContext
+    ///
+    /// This per-thread variable tracks if and how a transient
+    /// context is currently being used on the current thread
+    ///
+    /// \return The thread local TransientContext
+    ///
+    ////////////////////////////////////////////////////////////
+    static std::optional<TransientContext>& get()
+    {
+        thread_local std::optional<TransientContext> transientContext;
+        return transientContext;
+    }
+
     ///////////////////////////////////////////////////////////
     // Member data
     ////////////////////////////////////////////////////////////
     std::optional<sf::Context>             context;
     std::unique_lock<std::recursive_mutex> sharedContextLock;
+    std::shared_ptr<SharedContext>         sharedContext;
 };
 
-// This per-thread variable tracks if and how a transient
-// context is currently being used on the current thread
-thread_local std::optional<TransientContext> transientContext;
 
-// Supported OpenGL extensions
+// This structure contains all the implementation data we
-std::vector<std::string> extensions;
+// don't want to expose through the visible interface
-
+struct GlContext::Impl
-// Load our extensions vector with the supported extensions
-void loadExtensions()
 {
-    auto glGetErrorFunc    = reinterpret_cast<glGetErrorFuncType>(sf::priv::GlContext::getFunction("glGetError"));
+    ////////////////////////////////////////////////////////////
-    auto glGetIntegervFunc = reinterpret_cast<glGetIntegervFuncType>(sf::priv::GlContext::getFunction("glGetIntegerv"));
+    /// \brief Constructor
-    auto glGetStringFunc   = reinterpret_cast<glGetStringFuncType>(sf::priv::GlContext::getFunction("glGetString"));
+    ///
-
+    ////////////////////////////////////////////////////////////
-    if (!glGetErrorFunc || !glGetIntegervFunc || !glGetStringFunc)
+    Impl() :
-        return;
+    m_id(
-
+        []()
-    // Check whether a >= 3.0 context is available
-    int majorVersion = 0;
-    glGetIntegervFunc(GL_MAJOR_VERSION, &majorVersion);
-
-    auto glGetStringiFunc = reinterpret_cast<glGetStringiFuncType>(sf::priv::GlContext::getFunction("glGetStringi"));
-
-    if (glGetErrorFunc() == GL_INVALID_ENUM || !majorVersion || !glGetStringiFunc)
-    {
-        // Try to load the < 3.0 way
-        const char* extensionString = reinterpret_cast<const char*>(glGetStringFunc(GL_EXTENSIONS));
-
-        if (extensionString)
         {
-            extensions.clear();
+            static std::atomic<std::uint64_t> id(1); // start at 1, zero is "no context"
+            return id.fetch_add(1);
+        }())
+    {
+        auto& weakUnsharedGlObjects = getWeakUnsharedGlObjects();
+        unsharedGlObjects           = weakUnsharedGlObjects.lock();
 
-            do
+        if (!unsharedGlObjects)
-            {
+        {
-                const char* extension = extensionString;
+            unsharedGlObjects = std::make_shared<UnsharedGlObjects>();
 
-                while (*extensionString && (*extensionString != ' '))
+            weakUnsharedGlObjects = unsharedGlObjects;
-                    ++extensionString;
-
-                extensions.emplace_back(extension, extensionString);
-            } while (*extensionString++);
         }
     }
-    else
+
+    // Structure to track which unshared object belongs to which context
+    struct UnsharedGlObject
     {
-        // Try to load the >= 3.0 way
+        std::uint64_t         contextId;
-        int numExtensions = 0;
+        std::shared_ptr<void> object;
-        glGetIntegervFunc(GL_NUM_EXTENSIONS, &numExtensions);
+    };
 
-        if (numExtensions)
+    using UnsharedGlObjects = std::vector<UnsharedGlObject>;
-        {
-            extensions.clear();
 
-            for (unsigned int i = 0; i < static_cast<unsigned int>(numExtensions); ++i)
+    ////////////////////////////////////////////////////////////
-            {
+    /// \brief Get weak_ptr to unshared objects
-                const char* extensionString = reinterpret_cast<const char*>(glGetStringiFunc(GL_EXTENSIONS, i));
+    ///
-
+    /// \return weak_ptr to unshared objects
-                if (extensionString)
+    ///
-                    extensions.emplace_back(extensionString);
+    ////////////////////////////////////////////////////////////
-            }
+    static std::weak_ptr<UnsharedGlObjects>& getWeakUnsharedGlObjects()
-        }
-    }
-}
-
-// Helper to parse OpenGL version strings
-bool parseVersionString(const char* version, const char* prefix, unsigned int& major, unsigned int& minor)
-{
-    const std::size_t prefixLength = std::strlen(prefix);
-
-    if ((std::strlen(version) >= (prefixLength + 3)) && (std::strncmp(version, prefix, prefixLength) == 0) &&
-        std::isdigit(version[prefixLength]) && (version[prefixLength + 1] == '.') &&
-        std::isdigit(version[prefixLength + 2]))
     {
-        major = static_cast<unsigned int>(version[prefixLength] - '0');
+        static std::weak_ptr<UnsharedGlObjects> weakUnsharedGlObjects;
-        minor = static_cast<unsigned int>(version[prefixLength + 2] - '0');
 
-        return true;
+        return weakUnsharedGlObjects;
     }
 
-    return false;
+    ////////////////////////////////////////////////////////////
-}
+    /// \brief Get mutex protecting unshared objects
-} // namespace GlContextImpl
+    ///
-} // namespace
+    /// \return Mutex protecting unshared objects
+    ///
+    ////////////////////////////////////////////////////////////
+    static std::mutex& getUnsharedGlObjectsMutex()
+    {
+        static std::mutex mutex;
+        return mutex;
+    }
+
+    ///////////////////////////////////////////////////////////
+    // Member data
+    ////////////////////////////////////////////////////////////
+    std::shared_ptr<UnsharedGlObjects> unsharedGlObjects; //!< The current object's handle to unshared objects
+    const std::uint64_t m_id; //!< Unique identifier, used for identifying contexts when managing unshareable OpenGL resources
+};
 
 
-namespace sf::priv
-{
 ////////////////////////////////////////////////////////////
-void GlContext::initResource()
+std::shared_ptr<void> GlContext::getSharedContext()
 {
-    using GlContextImpl::loadExtensions;
+    return GlContext::SharedContext::get();
-    using GlContextImpl::mutex;
-    using GlContextImpl::resourceCount;
-    using GlContextImpl::sharedContext;
-
-    // Protect from concurrent access
-    const std::lock_guard lock(mutex);
-
-    // If this is the very first resource, trigger the global context initialization
-    if (resourceCount == 0)
-    {
-        if (sharedContext)
-        {
-            // Increment the resources counter
-            ++resourceCount;
-
-            return;
-        }
-
-        // Create the shared context
-        sharedContext = std::make_unique<ContextType>(nullptr);
-        sharedContext->initialize(ContextSettings());
-
-        // Load our extensions vector
-        loadExtensions();
-
-        // Deactivate the shared context so that others can activate it when necessary
-        sharedContext->setActive(false);
-    }
-
-    // Increment the resources counter
-    ++resourceCount;
 }
 
 
 ////////////////////////////////////////////////////////////
-void GlContext::cleanupResource()
+void GlContext::registerUnsharedGlObject(std::shared_ptr<void> object)
 {
-    using GlContextImpl::mutex;
+    if (const std::lock_guard lock(Impl::getUnsharedGlObjectsMutex());
-    using GlContextImpl::resourceCount;
+        auto                  unsharedGlObjects = Impl::getWeakUnsharedGlObjects().lock())
-    using GlContextImpl::sharedContext;
+        unsharedGlObjects->emplace_back(Impl::UnsharedGlObject{GlContextImpl::CurrentContext::get().id, std::move(object)});
-
-    // Protect from concurrent access
-    const std::lock_guard lock(mutex);
-
-    // Decrement the resources counter
-    --resourceCount;
-
-    // If there's no more resource alive, we can trigger the global context cleanup
-    if (resourceCount == 0)
-    {
-        if (!sharedContext)
-            return;
-
-        // Destroy the shared context
-        sharedContext.reset();
-    }
 }
 
 
 ////////////////////////////////////////////////////////////
-void GlContext::registerContextDestroyCallback(ContextDestroyCallback callback, void* arg)
+void GlContext::unregisterUnsharedGlObject(std::shared_ptr<void> object)
 {
-    GlContextImpl::contextDestroyCallbacks.emplace(callback, arg);
+    if (const std::lock_guard lock(Impl::getUnsharedGlObjectsMutex());
+        auto                  unsharedGlObjects = Impl::getWeakUnsharedGlObjects().lock())
+    {
+        // Find the object in unshared objects and remove it if its associated context is currently active
+        // This will trigger the destructor of the object since shared_ptr
+        // in unshared objects should be the only one existing
+        auto iter = std::find_if(unsharedGlObjects->begin(),
+                                 unsharedGlObjects->end(),
+                                 [&](const Impl::UnsharedGlObject& obj) {
+                                     return (obj.object == object) &&
+                                            (obj.contextId == GlContextImpl::CurrentContext::get().id);
+                                 });
+
+        if (iter != unsharedGlObjects->end())
+            unsharedGlObjects->erase(iter);
+    }
 }
 
 
 ////////////////////////////////////////////////////////////
 void GlContext::acquireTransientContext()
 {
-    using GlContextImpl::currentContext;
+    auto& currentContext = GlContextImpl::CurrentContext::get();
-    using GlContextImpl::TransientContext;
-    using GlContextImpl::transientContext;
 
     // Fast path if we already have a context active on this thread
     if (currentContext.id)
@@ -443,7 +524,7 @@ void GlContext::acquireTransientContext()
 
     // If currentContextId is not set, this must be the first
     // TransientContextLock on this thread, construct the state object
-    transientContext.emplace();
+    TransientContext::get().emplace();
 
     // Make sure a context is active at this point
     assert(currentContext.id);
@@ -453,8 +534,7 @@ void GlContext::acquireTransientContext()
 ////////////////////////////////////////////////////////////
 void GlContext::releaseTransientContext()
 {
-    using GlContextImpl::currentContext;
+    auto& currentContext = GlContextImpl::CurrentContext::get();
-    using GlContextImpl::transientContext;
 
     // Make sure a context was left active after acquireTransientContext() was called
     assert(currentContext.id);
@@ -468,34 +548,29 @@ void GlContext::releaseTransientContext()
 
     // If currentContextId is set and currentContextTransientCount is 0,
     // this is the last TransientContextLock that is released, destroy the state object
-    transientContext.reset();
+    TransientContext::get().reset();
 }
 
 
 ////////////////////////////////////////////////////////////
 std::unique_ptr<GlContext> GlContext::create()
 {
-    using GlContextImpl::mutex;
-    using GlContextImpl::sharedContext;
-
     // Make sure that there's an active context (context creation may need extensions, and thus a valid context)
-    assert(sharedContext != nullptr);
+    auto sharedContext = SharedContext::get();
 
-    const std::lock_guard lock(mutex);
+    const std::lock_guard lock(sharedContext->mutex);
 
     std::unique_ptr<GlContext> context;
 
     // We don't use acquireTransientContext here since we have
     // to ensure we have exclusive access to the shared context
     // in order to make sure it is not active during context creation
-    {
+    sharedContext->context->setActive(true);
-        sharedContext->setActive(true);
 
-        // Create the context
+    // Create the context
-        context = std::make_unique<ContextType>(sharedContext.get());
+    context = std::make_unique<ContextType>(&sharedContext->context.value());
 
-        sharedContext->setActive(false);
+    sharedContext->context->setActive(false);
-    }
 
     context->initialize(ContextSettings());
 
@@ -506,31 +581,26 @@ std::unique_ptr<GlContext> GlContext::create()
 ////////////////////////////////////////////////////////////
 std::unique_ptr<GlContext> GlContext::create(const ContextSettings& settings, const WindowImpl& owner, unsigned int bitsPerPixel)
 {
-    using GlContextImpl::loadExtensions;
-    using GlContextImpl::mutex;
-    using GlContextImpl::resourceCount;
-    using GlContextImpl::sharedContext;
-
     // Make sure that there's an active context (context creation may need extensions, and thus a valid context)
-    assert(sharedContext != nullptr);
+    auto sharedContext = SharedContext::get();
 
-    const std::lock_guard lock(mutex);
+    const std::lock_guard lock(sharedContext->mutex);
 
-    // If resourceCount is 1 we know that we are inside sf::Context or sf::Window
+    // If use_count is 2 (GlResource + sharedContext) we know that we are inside sf::Context or sf::Window
     // Only in this situation we allow the user to indirectly re-create the shared context as a core context
 
     // Check if we need to convert our shared context into a core context
-    if ((resourceCount == 1) && (settings.attributeFlags & ContextSettings::Core) &&
+    if ((sharedContext.use_count() == 2) && (settings.attributeFlags & ContextSettings::Core) &&
-        !(sharedContext->m_settings.attributeFlags & ContextSettings::Core))
+        !(sharedContext->context->m_settings.attributeFlags & ContextSettings::Core))
     {
         // Re-create our shared context as a core context
         const ContextSettings sharedSettings(0, 0, 0, settings.majorVersion, settings.minorVersion, settings.attributeFlags);
 
-        sharedContext = std::make_unique<ContextType>(nullptr, sharedSettings, Vector2u(1, 1));
+        sharedContext->context.emplace(nullptr, sharedSettings, Vector2u(1, 1));
-        sharedContext->initialize(sharedSettings);
+        sharedContext->context->initialize(sharedSettings);
 
         // Reload our extensions vector
-        loadExtensions();
+        sharedContext->loadExtensions();
     }
 
     std::unique_ptr<GlContext> context;
@@ -538,14 +608,12 @@ std::unique_ptr<GlContext> GlContext::create(const ContextSettings& settings, co
     // We don't use acquireTransientContext here since we have
     // to ensure we have exclusive access to the shared context
     // in order to make sure it is not active during context creation
-    {
+    sharedContext->context->setActive(true);
-        sharedContext->setActive(true);
 
-        // Create the context
+    // Create the context
-        context = std::make_unique<ContextType>(sharedContext.get(), settings, owner, bitsPerPixel);
+    context = std::make_unique<ContextType>(&sharedContext->context.value(), settings, owner, bitsPerPixel);
 
-        sharedContext->setActive(false);
+    sharedContext->context->setActive(false);
-    }
 
     context->initialize(settings);
     context->checkSettings(settings);
@@ -557,31 +625,26 @@ std::unique_ptr<GlContext> GlContext::create(const ContextSettings& settings, co
 ////////////////////////////////////////////////////////////
 std::unique_ptr<GlContext> GlContext::create(const ContextSettings& settings, const Vector2u& size)
 {
-    using GlContextImpl::loadExtensions;
-    using GlContextImpl::mutex;
-    using GlContextImpl::resourceCount;
-    using GlContextImpl::sharedContext;
-
     // Make sure that there's an active context (context creation may need extensions, and thus a valid context)
-    assert(sharedContext != nullptr);
+    auto sharedContext = SharedContext::get();
 
-    const std::lock_guard lock(mutex);
+    const std::lock_guard lock(sharedContext->mutex);
 
-    // If resourceCount is 1 we know that we are inside sf::Context or sf::Window
+    // If use_count is 2 (GlResource + sharedContext) we know that we are inside sf::Context or sf::Window
     // Only in this situation we allow the user to indirectly re-create the shared context as a core context
 
     // Check if we need to convert our shared context into a core context
-    if ((resourceCount == 1) && (settings.attributeFlags & ContextSettings::Core) &&
+    if ((sharedContext.use_count() == 2) && (settings.attributeFlags & ContextSettings::Core) &&
-        !(sharedContext->m_settings.attributeFlags & ContextSettings::Core))
+        !(sharedContext->context->m_settings.attributeFlags & ContextSettings::Core))
     {
         // Re-create our shared context as a core context
         const ContextSettings sharedSettings(0, 0, 0, settings.majorVersion, settings.minorVersion, settings.attributeFlags);
 
-        sharedContext = std::make_unique<ContextType>(nullptr, sharedSettings, Vector2u(1, 1));
+        sharedContext->context.emplace(nullptr, sharedSettings, Vector2u(1, 1));
-        sharedContext->initialize(sharedSettings);
+        sharedContext->context->initialize(sharedSettings);
 
         // Reload our extensions vector
-        loadExtensions();
+        sharedContext->loadExtensions();
     }
 
     std::unique_ptr<GlContext> context;
@@ -589,14 +652,12 @@ std::unique_ptr<GlContext> GlContext::create(const ContextSettings& settings, co
     // We don't use acquireTransientContext here since we have
     // to ensure we have exclusive access to the shared context
     // in order to make sure it is not active during context creation
-    {
+    sharedContext->context->setActive(true);
-        sharedContext->setActive(true);
 
-        // Create the context
+    // Create the context
-        context = std::make_unique<ContextType>(sharedContext.get(), settings, size);
+    context = std::make_unique<ContextType>(&sharedContext->context.value(), settings, size);
 
-        sharedContext->setActive(false);
+    sharedContext->context->setActive(false);
-    }
 
     context->initialize(settings);
     context->checkSettings(settings);
@@ -608,15 +669,27 @@ std::unique_ptr<GlContext> GlContext::create(const ContextSettings& settings, co
 ////////////////////////////////////////////////////////////
 bool GlContext::isExtensionAvailable(const char* name)
 {
-    using GlContextImpl::extensions;
+    // If this function is called before any context is available,
-    return std::find(extensions.begin(), extensions.end(), name) != extensions.end();
+    // the shared context will be created for the duration of this call
+    const auto sharedContext = SharedContext::get();
+
+    return std::find(sharedContext->extensions.begin(), sharedContext->extensions.end(), name) !=
+           sharedContext->extensions.end();
 }
 
 
 ////////////////////////////////////////////////////////////
 GlFunctionPointer GlContext::getFunction(const char* name)
 {
-    const std::lock_guard lock(GlContextImpl::mutex);
+    // Make sure we don't try to create the shared context here since
+    // setActive can be called during construction and lead to infinite recursion
+    auto* sharedContext = SharedContext::getWeakPtr().lock().get();
+
+    // We can't and don't need to lock when we are currently creating the shared context
+    std::unique_lock<std::recursive_mutex> lock;
+
+    if (sharedContext)
+        lock = std::unique_lock(sharedContext->mutex);
 
     return ContextType::getFunction(name);
 }
@@ -625,27 +698,23 @@ GlFunctionPointer GlContext::getFunction(const char* name)
 ////////////////////////////////////////////////////////////
 const GlContext* GlContext::getActiveContext()
 {
-    using GlContextImpl::currentContext;
+    return GlContextImpl::CurrentContext::get().ptr;
-
-    return currentContext.ptr;
 }
 
 
 ////////////////////////////////////////////////////////////
 std::uint64_t GlContext::getActiveContextId()
 {
-    using GlContextImpl::currentContext;
+    return GlContextImpl::CurrentContext::get().id;
-
-    return currentContext.id;
 }
 
 
 ////////////////////////////////////////////////////////////
 GlContext::~GlContext()
 {
-    using GlContextImpl::currentContext;
+    auto& currentContext = GlContextImpl::CurrentContext::get();
 
-    if (m_id == currentContext.id)
+    if (m_impl->m_id == currentContext.id)
     {
         currentContext.id  = 0;
         currentContext.ptr = nullptr;
@@ -663,20 +732,27 @@ const ContextSettings& GlContext::getSettings() const
 ////////////////////////////////////////////////////////////
 bool GlContext::setActive(bool active)
 {
-    using GlContextImpl::currentContext;
+    auto& currentContext = GlContextImpl::CurrentContext::get();
-    using GlContextImpl::mutex;
+
+    // Make sure we don't try to create the shared context here since
+    // setActive can be called during construction and lead to infinite recursion
+    auto* sharedContext = SharedContext::getWeakPtr().lock().get();
 
     if (active)
     {
-        if (m_id != currentContext.id)
+        if (m_impl->m_id != currentContext.id)
         {
-            const std::lock_guard lock(mutex);
+            // We can't and don't need to lock when we are currently creating the shared context
+            std::unique_lock<std::recursive_mutex> lock;
+
+            if (sharedContext)
+                lock = std::unique_lock(sharedContext->mutex);
 
             // Activate the context
             if (makeCurrent(true))
             {
                 // Set it as the new current context for this thread
-                currentContext.id  = m_id;
+                currentContext.id  = m_impl->m_id;
                 currentContext.ptr = this;
                 return true;
             }
@@ -693,9 +769,13 @@ bool GlContext::setActive(bool active)
     }
     else
     {
-        if (m_id == currentContext.id)
+        if (m_impl->m_id == currentContext.id)
         {
-            const std::lock_guard lock(mutex);
+            // We can't and don't need to lock when we are currently creating the shared context
+            std::unique_lock<std::recursive_mutex> lock;
+
+            if (sharedContext)
+                lock = std::unique_lock(sharedContext->mutex);
 
             // Deactivate the context
             if (makeCurrent(false))
@@ -719,7 +799,7 @@ bool GlContext::setActive(bool active)
 
 
 ////////////////////////////////////////////////////////////
-GlContext::GlContext() : m_id(GlContextImpl::nextContextId.fetch_add(1))
+GlContext::GlContext() : m_impl(std::make_unique<Impl>())
 {
     // Nothing to do
 }
@@ -765,23 +845,34 @@ int GlContext::evaluateFormat(
 ////////////////////////////////////////////////////////////
 void GlContext::cleanupUnsharedResources()
 {
-    using GlContextImpl::ContextDestroyCallbacks;
+    const auto& currentContext = GlContextImpl::CurrentContext::get();
-    using GlContextImpl::contextDestroyCallbacks;
-    using GlContextImpl::currentContext;
 
     // Save the current context so we can restore it later
     GlContext* contextToRestore = currentContext.ptr;
 
     // If this context is already active there is no need to save it
-    if (m_id == currentContext.id)
+    if (m_impl->m_id == currentContext.id)
         contextToRestore = nullptr;
 
     // Make this context active so resources can be freed
     setActive(true);
 
-    // Call the registered destruction callbacks
+    {
-    for (auto& [callback, ptr] : contextDestroyCallbacks)
+        const std::lock_guard lock(Impl::getUnsharedGlObjectsMutex());
-        callback(ptr);
+
+        // Destroy the unshared objects contained in this context
+        for (auto iter = m_impl->unsharedGlObjects->begin(); iter != m_impl->unsharedGlObjects->end();)
+        {
+            if (iter->contextId == m_impl->m_id)
+            {
+                iter = m_impl->unsharedGlObjects->erase(iter);
+            }
+            else
+            {
+                ++iter;
+            }
+        }
+    }
 
     // Make the originally active context active again
     if (contextToRestore)
@@ -815,7 +906,7 @@ void GlContext::initialize(const ContextSettings& requestedSettings)
     glGetIntegervFunc(GL_MAJOR_VERSION, &majorVersion);
     glGetIntegervFunc(GL_MINOR_VERSION, &minorVersion);
 
-    if ((glGetErrorFunc() != GL_INVALID_ENUM) && (majorVersion != 0))
+    if (glGetErrorFunc() != GL_INVALID_ENUM)
     {
         m_settings.majorVersion = static_cast<unsigned int>(majorVersion);
         m_settings.minorVersion = static_cast<unsigned int>(minorVersion);
@@ -836,7 +927,24 @@ void GlContext::initialize(const ContextSettings& requestedSettings)
             // OpenGL ES Full profile:        The beginning of the returned string is "OpenGL ES major.minor"
             // Desktop OpenGL:                The beginning of the returned string is "major.minor"
 
-            using GlContextImpl::parseVersionString;
+            // Helper to parse OpenGL version strings
+            static const auto parseVersionString =
+                [](const char* versionString, const char* prefix, unsigned int& major, unsigned int& minor)
+            {
+                const std::size_t prefixLength = std::strlen(prefix);
+
+                if ((std::strlen(versionString) >= (prefixLength + 3)) &&
+                    (std::strncmp(versionString, prefix, prefixLength) == 0) && std::isdigit(versionString[prefixLength]) &&
+                    (versionString[prefixLength + 1] == '.') && std::isdigit(versionString[prefixLength + 2]))
+                {
+                    major = static_cast<unsigned int>(versionString[prefixLength] - '0');
+                    minor = static_cast<unsigned int>(versionString[prefixLength + 2] - '0');
+
+                    return true;
+                }
+
+                return false;
+            };
 
             if (!parseVersionString(version, "OpenGL ES-CL ", m_settings.majorVersion, m_settings.minorVersion) &&
                 !parseVersionString(version, "OpenGL ES-CM ", m_settings.majorVersion, m_settings.minorVersion) &&

src/SFML/Window/GlContext.hpp

@@ -50,38 +50,32 @@ class GlContext
 {
 public:
     ////////////////////////////////////////////////////////////
-    /// \brief Perform resource initialization
+    /// \brief Get a shared_ptr to the shared context
     ///
-    /// This function is called every time an OpenGL resource is
+    /// \return shared_ptr to the shared context
-    /// created. When the first resource is initialized, it makes
-    /// sure that everything is ready for contexts to work properly.
     ///
     ////////////////////////////////////////////////////////////
-    static void initResource();
+    static std::shared_ptr<void> getSharedContext();
 
     ////////////////////////////////////////////////////////////
-    /// \brief Perform resource cleanup
+    /// \brief Register an OpenGL object to be destroyed when its containing context is destroyed
-    ///
-    /// This function is called every time an OpenGL resource is
-    /// destroyed. When the last resource is destroyed, it makes
-    /// sure that everything that was created by initResource()
-    /// is properly released.
-    ///
-    ////////////////////////////////////////////////////////////
-    static void cleanupResource();
-
-    ////////////////////////////////////////////////////////////
-    /// \brief Register a function to be called when a context is destroyed
     ///
     /// This is used for internal purposes in order to properly
     /// clean up OpenGL resources that cannot be shared bwteen
     /// contexts.
     ///
-    /// \param callback Function to be called when a context is destroyed
+    /// \param object Object to be destroyed when its containing context is destroyed
-    /// \param arg      Argument to pass when calling the function
     ///
     ////////////////////////////////////////////////////////////
-    static void registerContextDestroyCallback(ContextDestroyCallback callback, void* arg);
+    static void registerUnsharedGlObject(std::shared_ptr<void> object);
+
+    ////////////////////////////////////////////////////////////
+    /// \brief Unregister an OpenGL object from its containing context
+    ///
+    /// \param object Object to be unregister
+    ///
+    ////////////////////////////////////////////////////////////
+    static void unregisterUnsharedGlObject(std::shared_ptr<void> object);
 
     ////////////////////////////////////////////////////////////
     /// \brief Acquires a context for short-term use on the current thread
@@ -300,6 +294,10 @@ protected:
     ContextSettings m_settings; //!< Creation settings of the context
 
 private:
+    struct TransientContext;
+    struct SharedContext;
+    struct Impl;
+
     ////////////////////////////////////////////////////////////
     /// \brief Perform various initializations after the context construction
     /// \param requestedSettings Requested settings during context creation
@@ -317,7 +315,7 @@ private:
     ////////////////////////////////////////////////////////////
     // Member data
     ////////////////////////////////////////////////////////////
-    const std::uint64_t m_id; //!< Unique number that identifies the context
+    const std::unique_ptr<Impl> m_impl; //!< Implementation details
 };
 
 } // namespace sf::priv

src/SFML/Window/GlResource.cpp

@@ -32,23 +32,22 @@
 namespace sf
 {
 ////////////////////////////////////////////////////////////
-GlResource::GlResource()
+GlResource::GlResource() : m_sharedContext(priv::GlContext::getSharedContext())
 {
-    priv::GlContext::initResource();
 }
 
 
 ////////////////////////////////////////////////////////////
-GlResource::~GlResource()
+void GlResource::registerUnsharedGlObject(std::shared_ptr<void> object)
 {
-    priv::GlContext::cleanupResource();
+    priv::GlContext::registerUnsharedGlObject(std::move(object));
 }
 
 
 ////////////////////////////////////////////////////////////
-void GlResource::registerContextDestroyCallback(ContextDestroyCallback callback, void* arg)
+void GlResource::unregisterUnsharedGlObject(std::shared_ptr<void> object)
 {
-    priv::GlContext::registerContextDestroyCallback(callback, arg);
+    priv::GlContext::unregisterUnsharedGlObject(std::move(object));
 }
 
 

test/Window/GlResource.test.cpp

@@ -3,7 +3,7 @@
 #include <type_traits>
 
 static_assert(!std::is_constructible_v<sf::GlResource>);
-static_assert(!std::is_copy_constructible_v<sf::GlResource>);
+static_assert(std::is_copy_constructible_v<sf::GlResource>);
 static_assert(std::is_copy_assignable_v<sf::GlResource>);
-static_assert(!std::is_nothrow_move_constructible_v<sf::GlResource>);
+static_assert(std::is_nothrow_move_constructible_v<sf::GlResource>);
 static_assert(std::is_nothrow_move_assignable_v<sf::GlResource>);