From 21af6fecf142882b08e1f2aa006bb406a3631e96 Mon Sep 17 00:00:00 2001
From: binary1248 <binary1248@hotmail.com>
Date: Sun, 26 Mar 2023 04:44:05 +0200
Subject: [PATCH] Fixed OpenGL entry points being loaded from OpenGL32.dll
 instead of failing to load if they are not provided by the vendor provided
 library on Windows.

---
 src/SFML/Window/GlContext.cpp        | 23 ---------------
 src/SFML/Window/Win32/WglContext.cpp | 42 ++++++++++++++++++++++------
 src/SFML/Window/Win32/WglContext.hpp |  1 +
 3 files changed, 34 insertions(+), 32 deletions(-)

diff --git a/src/SFML/Window/GlContext.cpp b/src/SFML/Window/GlContext.cpp
index ce7336ac..636ed6cd 100644
--- a/src/SFML/Window/GlContext.cpp
+++ b/src/SFML/Window/GlContext.cpp
@@ -945,29 +945,6 @@ void GlContext::initialize(const ContextSettings& requestedSettings)
 void GlContext::checkSettings(const ContextSettings& requestedSettings) const
 {
     // Perform checks to inform the user if they are getting a context they might not have expected
-
-    auto glGetStringFunc = reinterpret_cast<glGetStringFuncType>(getFunction("glGetString"));
-
-    if (!glGetStringFunc)
-    {
-        err() << "Could not load glGetString function" << std::endl;
-
-        return;
-    }
-
-    // Detect any known non-accelerated implementations and warn
-    const char* vendorName   = reinterpret_cast<const char*>(glGetStringFunc(GL_VENDOR));
-    const char* rendererName = reinterpret_cast<const char*>(glGetStringFunc(GL_RENDERER));
-
-    if (vendorName && rendererName)
-    {
-        if (std::string_view(vendorName) == "Microsoft Corporation" && std::string_view(rendererName) == "GDI Generic")
-        {
-            err() << "Warning: Detected \"Microsoft Corporation GDI Generic\" OpenGL implementation" << '\n'
-                  << "The current OpenGL implementation is not hardware-accelerated" << std::endl;
-        }
-    }
-
     int version          = static_cast<int>(m_settings.majorVersion * 10u + m_settings.minorVersion);
     int requestedVersion = static_cast<int>(requestedSettings.majorVersion * 10u + requestedSettings.minorVersion);
 
diff --git a/src/SFML/Window/Win32/WglContext.cpp b/src/SFML/Window/Win32/WglContext.cpp
index 0833f84f..7d6016e3 100644
--- a/src/SFML/Window/Win32/WglContext.cpp
+++ b/src/SFML/Window/Win32/WglContext.cpp
@@ -51,6 +51,18 @@ namespace WglContextImpl
 thread_local sf::priv::WglContext* currentContext(nullptr);
 
 
+// We use a different loader for wgl functions since we load them directly from OpenGL32.dll
+sf::GlFunctionPointer getOpenGl32Function(const char* name)
+{
+    static const HMODULE module = GetModuleHandleA("OpenGL32.dll");
+
+    if (module)
+        return reinterpret_cast<sf::GlFunctionPointer>(GetProcAddress(module, reinterpret_cast<LPCSTR>(name)));
+
+    return nullptr;
+}
+
+
 ////////////////////////////////////////////////////////////
 void ensureInit()
 {
@@ -59,7 +71,7 @@ void ensureInit()
     {
         initialized = true;
 
-        gladLoadWGL(nullptr, sf::priv::WglContext::getFunction);
+        gladLoadWGL(nullptr, getOpenGl32Function);
     }
 }
 
@@ -74,7 +86,7 @@ void ensureExtensionsInit(HDC deviceContext)
 
         // We don't check the return value since the extension
         // flags are cleared even if loading fails
-        gladLoadWGL(deviceContext, sf::priv::WglContext::getFunction);
+        gladLoadWGL(deviceContext, getOpenGl32Function);
     }
 }
 } // namespace WglContextImpl
@@ -186,6 +198,8 @@ WglContext::~WglContext()
 ////////////////////////////////////////////////////////////
 GlFunctionPointer WglContext::getFunction(const char* name)
 {
+    assert(WglContextImpl::currentContext != nullptr);
+
     auto address = reinterpret_cast<GlFunctionPointer>(wglGetProcAddress(reinterpret_cast<LPCSTR>(name)));
 
     if (address)
@@ -197,13 +211,9 @@ GlFunctionPointer WglContext::getFunction(const char* name)
             return address;
     }
 
-    static HMODULE module = nullptr;
-
-    if (!module)
-        module = GetModuleHandleA("OpenGL32.dll");
-
-    if (module)
-        return reinterpret_cast<GlFunctionPointer>(GetProcAddress(module, reinterpret_cast<LPCSTR>(name)));
+    // If we are using the generic GDI implementation, try loading directly from OpenGL32.dll as well
+    if (WglContextImpl::currentContext->m_isGeneric)
+        return WglContextImpl::getOpenGl32Function(name);
 
     return nullptr;
 }
@@ -460,6 +470,20 @@ void WglContext::updateSettingsFromPixelFormat()
         return;
     }
 
+    // Detect if we are running using the generic GDI implementation and warn
+    if (actualFormat.dwFlags & PFD_GENERIC_FORMAT)
+    {
+        m_isGeneric = true;
+
+        err() << "Warning: Detected \"Microsoft Corporation GDI Generic\" OpenGL implementation" << std::endl;
+
+        // Detect if the generic GDI implementation is not accelerated
+        if (!(actualFormat.dwFlags & PFD_GENERIC_ACCELERATED))
+            err() << "Warning: The \"Microsoft Corporation GDI Generic\" OpenGL implementation is not "
+                     "hardware-accelerated"
+                  << std::endl;
+    }
+
     if (SF_GLAD_WGL_ARB_pixel_format)
     {
         const int attributes[] = {WGL_DEPTH_BITS_ARB, WGL_STENCIL_BITS_ARB};
diff --git a/src/SFML/Window/Win32/WglContext.hpp b/src/SFML/Window/Win32/WglContext.hpp
index 54be1964..1624409c 100644
--- a/src/SFML/Window/Win32/WglContext.hpp
+++ b/src/SFML/Window/Win32/WglContext.hpp
@@ -181,6 +181,7 @@ private:
     HDC         m_deviceContext{}; //!< Device context associated to the context
     HGLRC       m_context{};       //!< OpenGL context
     bool        m_ownsWindow{};    //!< Do we own the target window?
+    bool        m_isGeneric{};     //!< Is this context provided by the generic GDI implementation?
 };
 
 } // namespace sf::priv