Backends: GLFW: Load X11 functions dynamically to avoid x11 linking requirement. (#9116, #9109)

Amend 6b2cdf2 (#8884, #8474, #8289)

backends/imgui_impl_glfw.cpp

@@ -32,6 +32,7 @@
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
 //  2025-XX-XX: Platform: Added support for multiple windows via the ImGuiPlatformIO interface.
+//  2026-01-18: [Docking] Dynamically load X11 functions to avoid -lx11 linking requirement introduced on 2025-09-10.
 //  2025-12-12: Added IMGUI_IMPL_GLFW_DISABLE_X11 / IMGUI_IMPL_GLFW_DISABLE_WAYLAND to forcefully disable either.
 //  2025-12-10: Avoid repeated glfwSetCursor()/glfwSetInputMode() calls when unnecessary. Lowers overhead for very high framerates (e.g. 10k+ FPS).
 //  2025-11-06: Lower minimum requirement to GLFW 3.0. Though a recent version e.g GLFW 3.4 is highly recommended.
@@ -147,6 +148,7 @@
 #ifndef GLFW_EXPOSE_NATIVE_X11      // for glfwGetX11Display(), glfwGetX11Window() on Freedesktop (Linux, BSD, etc.)
 #define GLFW_EXPOSE_NATIVE_X11
 #include <X11/Xatom.h>
+#include <dlfcn.h>              // for dlopen()
 #endif
 #include <GLFW/glfw3native.h>
 #undef Status                   // X11 headers are leaking this.
@@ -215,6 +217,13 @@ enum GlfwClientApi
     GlfwClientApi_Unknown,  // Anything else fits here.
 };
 
+#if GLFW_HAS_X11
+typedef Atom (*PFN_XInternAtom)(Display*, const char* ,Bool);
+typedef int  (*PFN_XChangeProperty)(Display*, Window, Atom, Atom, int, int, const unsigned char*, int);
+typedef int  (*PFN_XChangeWindowAttributes)(Display*, Window, unsigned long, XSetWindowAttributes*);
+typedef int  (*PFN_XFlush)(Display*);
+#endif
+
 // GLFW data
 struct ImGui_ImplGlfw_Data
 {
@@ -252,6 +261,15 @@ struct ImGui_ImplGlfw_Data
     WNDPROC                 PrevWndProc;
 #endif
 
+#if GLFW_HAS_X11
+    // Module and function pointers loaded at initialization to avoid linking statically with X11.
+    void*                       X11Module;
+    PFN_XInternAtom             XInternAtom;
+    PFN_XChangeProperty         XChangeProperty;
+    PFN_XChangeWindowAttributes XChangeWindowAttributes;
+    PFN_XFlush                  XFlush;
+#endif
+
     ImGui_ImplGlfw_Data()   { memset((void*)this, 0, sizeof(*this)); }
 };
 
@@ -792,6 +810,26 @@ static bool ImGui_ImplGlfw_Init(GLFWwindow* window, bool install_callbacks, Glfw
     ::SetWindowLongPtrW((HWND)main_viewport->PlatformHandleRaw, GWLP_WNDPROC, (LONG_PTR)ImGui_ImplGlfw_WndProc);
 #endif
 
+#if GLFW_HAS_X11
+    if (!bd->IsWayland)
+    {
+        // Load X11 module dynamically. Copied from the way that GLFW does it in x11_init.c
+#if defined(__CYGWIN__)
+        const char* x11_module_path = "libX11-6.so";
+#elif defined(__OpenBSD__) || defined(__NetBSD__)
+        const char* x11_module_path = "libX11.so";
+#else
+        const char* x11_module_path = "libX11.so.6";
+#endif
+        bd->X11Module = dlopen(x11_module_path, RTLD_LAZY | RTLD_LOCAL);
+        bd->XInternAtom = (PFN_XInternAtom)dlsym(bd->X11Module, "XInternAtom");
+        bd->XChangeProperty = (PFN_XChangeProperty)dlsym(bd->X11Module, "XChangeProperty");
+        bd->XChangeWindowAttributes = (PFN_XChangeWindowAttributes)dlsym(bd->X11Module, "XChangeWindowAttributes");
+        bd->XFlush = (PFN_XFlush)dlsym(bd->X11Module, "XFlush");
+        IM_ASSERT(bd->XInternAtom != nullptr && bd->XChangeProperty != nullptr && bd->XChangeWindowAttributes != nullptr && bd->XFlush != nullptr);
+    }
+#endif
+
     // Emscripten: the same application can run on various platforms, so we detect the Apple platform at runtime
     // to override io.ConfigMacOSXBehaviors from its default (which is always false in Emscripten).
 #ifdef __EMSCRIPTEN__
@@ -855,6 +893,11 @@ void ImGui_ImplGlfw_Shutdown()
     bd->PrevWndProc = nullptr;
 #endif
 
+#if GLFW_HAS_X11
+    if (bd->X11Module != nullptr)
+        dlclose(bd->X11Module);
+#endif
+
     io.BackendPlatformName = nullptr;
     io.BackendPlatformUserData = nullptr;
     io.BackendFlags &= ~(ImGuiBackendFlags_HasMouseCursors | ImGuiBackendFlags_HasSetMousePos | ImGuiBackendFlags_HasGamepad | ImGuiBackendFlags_PlatformHasViewports | ImGuiBackendFlags_HasMouseHoveredViewport);
@@ -1272,20 +1315,20 @@ static void ImGui_ImplGlfw_WindowSizeCallback(GLFWwindow* window, int, int)
 
 #if !defined(__APPLE__) && !defined(_WIN32) && !defined(__EMSCRIPTEN__) && GLFW_HAS_GETPLATFORM
 #define IMGUI_GLFW_HAS_SETWINDOWFLOATING
-static void ImGui_ImplGlfw_SetWindowFloating(GLFWwindow* window)
+static void ImGui_ImplGlfw_SetWindowFloating(ImGui_ImplGlfw_Data* bd, GLFWwindow* window)
 {
 #ifdef GLFW_EXPOSE_NATIVE_X11
     if (glfwGetPlatform() == GLFW_PLATFORM_X11)
     {
         Display* display = glfwGetX11Display();
         Window xwindow = glfwGetX11Window(window);
-        Atom wm_type = XInternAtom(display, "_NET_WM_WINDOW_TYPE", False);
-        Atom wm_type_dialog = XInternAtom(display, "_NET_WM_WINDOW_TYPE_DIALOG", False);
-        XChangeProperty(display, xwindow, wm_type, XA_ATOM, 32, PropModeReplace, (unsigned char*)&wm_type_dialog, 1);
+        Atom wm_type = bd->XInternAtom(display, "_NET_WM_WINDOW_TYPE", False);
+        Atom wm_type_dialog = bd->XInternAtom(display, "_NET_WM_WINDOW_TYPE_DIALOG", False);
+        bd->XChangeProperty(display, xwindow, wm_type, XA_ATOM, 32, PropModeReplace, (unsigned char*)&wm_type_dialog, 1);
         XSetWindowAttributes attrs;
         attrs.override_redirect = False;
-        XChangeWindowAttributes(display, xwindow, CWOverrideRedirect, &attrs);
-        XFlush(display);
+        bd->XChangeWindowAttributes(display, xwindow, CWOverrideRedirect, &attrs);
+        bd->XFlush(display);
     }
 #endif // GLFW_EXPOSE_NATIVE_X11
 #ifdef GLFW_EXPOSE_NATIVE_WAYLAND
@@ -1322,7 +1365,7 @@ static void ImGui_ImplGlfw_CreateWindow(ImGuiViewport* viewport)
     ImGui_ImplGlfw_ContextMap_Add(vd->Window, bd->Context);
     viewport->PlatformHandle = (void*)vd->Window;
 #ifdef IMGUI_GLFW_HAS_SETWINDOWFLOATING
-    ImGui_ImplGlfw_SetWindowFloating(vd->Window);
+    ImGui_ImplGlfw_SetWindowFloating(bd, vd->Window);
 #endif
 #ifdef _WIN32
     viewport->PlatformHandleRaw = glfwGetWin32Window(vd->Window);

docs/CHANGELOG.txt

@@ -185,6 +185,8 @@ Docking+Viewports Branch:
   gamepad/keyboard to move a window to another viewport. (#9053) [@lut0pia, @ocornut]
 - Fixed implicit/fallback "Debug" window from staying visible if once docked. (#9151)
 - Backends:
+  - GLFW: dynamically load X11 functions to avoid -lx11 linking requirement introduced
+    in 1.92.3. (#9116, #9109) [@ramenguy99]
   - SDL2, SDL3: adjust IME offset to match other backends and master branch. (#6071, #1953)
   - Win32: viewports created by backend forcefully direct messages to
     DefWindowProcW() in order to support Unicode text input. (#9099, #3653, #5961) [@ulhc]

examples/example_glfw_opengl2/Makefile

@@ -33,7 +33,7 @@ LIBS =
 
 ifeq ($(UNAME_S), Linux) #LINUX
 	ECHO_MESSAGE = "Linux"
-	LIBS += $(LINUX_GL_LIBS) -lX11 `pkg-config --static --libs glfw3`
+	LIBS += $(LINUX_GL_LIBS) `pkg-config --static --libs glfw3`
 
 	CXXFLAGS += `pkg-config --cflags glfw3`
 	CFLAGS = $(CXXFLAGS)

examples/example_glfw_opengl3/Makefile

@@ -41,7 +41,7 @@ LIBS =
 
 ifeq ($(UNAME_S), Linux) #LINUX
 	ECHO_MESSAGE = "Linux"
-	LIBS += $(LINUX_GL_LIBS) -lX11 `pkg-config --static --libs glfw3`
+	LIBS += $(LINUX_GL_LIBS) `pkg-config --static --libs glfw3`
 
 	CXXFLAGS += `pkg-config --cflags glfw3`
 	CFLAGS = $(CXXFLAGS)

examples/example_glfw_vulkan/CMakeLists.txt

@@ -36,7 +36,6 @@ find_package(Vulkan REQUIRED)
   #NAMES vulkan vulkan-1)
 #set(LIBRARIES "glfw;${VULKAN_LIBRARY}")
 set(LIBRARIES "glfw;Vulkan::Vulkan")
-# FIXME: Linux needs linking with "X11" as well?
 
 # Use vulkan headers from glfw:
 include_directories(${GLFW_DIR}/deps)

examples/example_glfw_vulkan/Makefile

@@ -33,7 +33,7 @@ LIBS =
 
 ifeq ($(UNAME_S), Linux) #LINUX
 	ECHO_MESSAGE = "Linux"
-	LIBS += $(LINUX_GL_LIBS) -lX11 `pkg-config --static --libs glfw3 vulkan`
+	LIBS += $(LINUX_GL_LIBS) `pkg-config --static --libs glfw3 vulkan`
 
 	CXXFLAGS += `pkg-config --cflags glfw3 vulkan`
 	CFLAGS = $(CXXFLAGS)