Backends: OpenGL3: add and call embedded loader shutdown in ImGui_ImplOpenGL3_Shutdown(). (#8792)

Include update of imgui_impl_opengl3_loader.h as submitted to gl3w_stripped repository, which adds imgl3wShutdown().

backends/imgui_impl_opengl3.cpp

@@ -23,6 +23,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2025-07-22: OpenGL: Add and call embedded loader shutdown during ImGui_ImplOpenGL3_Shutdown() to facilitate multiple init/shutdown cycles in same process. (#8792)
 //  2025-07-15: OpenGL: Set GL_UNPACK_ALIGNMENT to 1 before updating textures (#8802) + restore non-WebGL/ES update path that doesn't require a CPU-side copy.
 //  2025-06-11: OpenGL: Added support for ImGuiBackendFlags_RendererHasTextures, for dynamic font atlas. Removed ImGui_ImplOpenGL3_CreateFontsTexture() and ImGui_ImplOpenGL3_DestroyFontsTexture().
 //  2025-06-04: OpenGL: Made GLES 3.20 contexts not access GL_CONTEXT_PROFILE_MASK nor GL_PRIMITIVE_RESTART. (#8664)
@@ -422,6 +423,10 @@ void    ImGui_ImplOpenGL3_Shutdown()
     io.BackendRendererUserData = nullptr;
     io.BackendFlags &= ~(ImGuiBackendFlags_RendererHasVtxOffset | ImGuiBackendFlags_RendererHasTextures);
     IM_DELETE(bd);
+
+#ifdef IMGUI_IMPL_OPENGL_LOADER_IMGL3W
+    imgl3wShutdown();
+#endif
 }
 
 void    ImGui_ImplOpenGL3_NewFrame()

backends/imgui_impl_opengl3_loader.h

@@ -477,6 +477,7 @@ typedef GL3WglProc (*GL3WGetProcAddressProc)(const char *proc);
 /* gl3w api */
 GL3W_API int imgl3wInit(void);
 GL3W_API int imgl3wInit2(GL3WGetProcAddressProc proc);
+GL3W_API void imgl3wShutdown(void);
 GL3W_API int imgl3wIsSupported(int major, int minor);
 GL3W_API GL3WglProc imgl3wGetProcAddress(const char *proc);
 
@@ -632,7 +633,7 @@ extern "C" {
 #endif
 #include <windows.h>
 
-static HMODULE libgl;
+static HMODULE libgl = NULL;
 typedef PROC(__stdcall* GL3WglGetProcAddr)(LPCSTR);
 static GL3WglGetProcAddr wgl_get_proc_address;
 
@@ -645,7 +646,7 @@ static int open_libgl(void)
     return GL3W_OK;
 }
 
-static void close_libgl(void) { FreeLibrary(libgl); }
+static void close_libgl(void) { FreeLibrary(libgl); libgl = NULL; }
 static GL3WglProc get_proc(const char *proc)
 {
     GL3WglProc res;
@@ -657,7 +658,7 @@ static GL3WglProc get_proc(const char *proc)
 #elif defined(__APPLE__)
 #include <dlfcn.h>
 
-static void *libgl;
+static void *libgl = NULL;
 static int open_libgl(void)
 {
     libgl = dlopen("/System/Library/Frameworks/OpenGL.framework/OpenGL", RTLD_LAZY | RTLD_LOCAL);
@@ -666,7 +667,7 @@ static int open_libgl(void)
     return GL3W_OK;
 }
 
-static void close_libgl(void) { dlclose(libgl); }
+static void close_libgl(void) { dlclose(libgl); libgl = NULL; }
 
 static GL3WglProc get_proc(const char *proc)
 {
@@ -834,6 +835,11 @@ int imgl3wInit2(GL3WGetProcAddressProc proc)
     return parse_version();
 }
 
+void imgl3wShutdown(void)
+{
+    close_libgl();
+}
+
 int imgl3wIsSupported(int major, int minor)
 {
     if (major < 2)

docs/CHANGELOG.txt

@@ -50,6 +50,8 @@ Other Changes:
   and TableSetBgColor() calls. (#1651, #8499)
 - Misc: removed more redundant inline static linkage from imgui_internal.h to 
   facilitate using in C++ modules. (#8813, #8682, #8358) [@stripe2933]
+- Backends: OpenGL3: add and call embedded loader shutdown in ImGui_ImplOpenGL3_Shutdown() 
+  to facilitate multiple init/shutdown cycles in same process. (#8792) [@tim-rex]
 - Backends: OpenGL2, OpenGL3: set GL_UNPACK_ALIGNMENT to 1 before updating 
   textures. (#8802) [@Daandelange]