Backends: GLFW: improve multi-viewport behavior in tiling WMs (X11). Amends. (#8884, #8474, #8289)

Author: ocornut

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.
+//  2025-09-10: [Docking] Improve multi-viewport behavior in tiling WMs on X11 via the ImGui_ImplGlfw_SetWindowFloating() function. Note: using GLFW backend on Linux/BSD etc. requires linking with -lX11. (#8884, #8474, #8289)
 //  2025-07-08: Made ImGui_ImplGlfw_GetContentScaleForWindow(), ImGui_ImplGlfw_GetContentScaleForMonitor() helpers return 1.0f on Emscripten and Android platforms, matching macOS logic. (#8742, #8733)
 //  2025-06-18: Added support for multiple Dear ImGui contexts. (#8676, #8239, #8069)
 //  2025-06-11: Added ImGui_ImplGlfw_GetContentScaleForWindow(GLFWwindow* window) and ImGui_ImplGlfw_GetContentScaleForMonitor(GLFWmonitor* monitor) helper to facilitate making DPI-aware apps.
@@ -121,14 +122,13 @@
 #define GLFW_EXPOSE_NATIVE_WIN32
 #endif
 #include <GLFW/glfw3native.h>   // for glfwGetWin32Window()
-#endif
-#ifdef __APPLE__
+#elif defined(__APPLE__)
 #ifndef GLFW_EXPOSE_NATIVE_COCOA
 #define GLFW_EXPOSE_NATIVE_COCOA
 #endif
 #include <GLFW/glfw3native.h>   // for glfwGetCocoaWindow()
 #elif !defined(__EMSCRIPTEN__)
-// Freedesktop(Linux, BSD, etc)
+// Freedesktop (Linux, BSD, etc)
 #ifndef GLFW_EXPOSE_NATIVE_X11
 #define GLFW_EXPOSE_NATIVE_X11
 #include <X11/Xatom.h>
@@ -183,7 +183,7 @@
 #define GLFW_HAS_GETERROR               (GLFW_VERSION_COMBINED >= 3300) // 3.3+ glfwGetError()
 #define GLFW_HAS_GETPLATFORM            (GLFW_VERSION_COMBINED >= 3400) // 3.4+ glfwGetPlatform()
 
-// Map GLFWWindow* to ImGuiContext*. 
+// Map GLFWWindow* to ImGuiContext*.
 // - Would be simpler if we could use glfwSetWindowUserPointer()/glfwGetWindowUserPointer(), but this is a single and shared resource.
 // - Would be simpler if we could use e.g. std::map<> as well. But we don't.
 // - This is not particularly optimized as we expect size to be small and queries to be rare.
@@ -1200,29 +1200,29 @@ static void ImGui_ImplGlfw_WindowSizeCallback(GLFWwindow* window, int, int)
     }
 }
 
-#if !defined(__APPLE__) && !defined(_WIN32) && !defined(__EMSCRIPTEN__) && (GLFW_VERSION_MAJOR > 3 || (GLFW_VERSION_MAJOR == 3 && GLFW_VERSION_MINOR >= 4)) 
+#if !defined(__APPLE__) && !defined(_WIN32) && !defined(__EMSCRIPTEN__) && GLFW_HAS_GETPLATFORM
+#define IMGUI_GLFW_HAS_SETWINDOWFLOATING
 static void ImGui_ImplGlfw_SetWindowFloating(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);
-
+        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);
     }
-#endif
+#endif // GLFW_EXPOSE_NATIVE_X11
+#ifdef GLFW_EXPOSE_NATIVE_WAYLAND
+    // FIXME: Help needed, see #8884, #8474 for discussions about this.
+#endif // GLFW_EXPOSE_NATIVE_X11
 }
-#endif
+#endif // IMGUI_GLFW_HAS_SETWINDOWFLOATING
 
 static void ImGui_ImplGlfw_CreateWindow(ImGuiViewport* viewport)
 {
@@ -1251,7 +1251,7 @@ static void ImGui_ImplGlfw_CreateWindow(ImGuiViewport* viewport)
     vd->WindowOwned = true;
     ImGui_ImplGlfw_ContextMap_Add(vd->Window, bd->Context);
     viewport->PlatformHandle = (void*)vd->Window;
-#if !defined(__APPLE__) && !defined(_WIN31) && !defined(__EMSCRIPTEN__) && (GLFW_VERSION_MAJOR > 3 || (GLFW_VERSION_MAJOR == 3 && GLFW_VERSION_MINOR >= 4))
+#ifdef IMGUI_GLFW_HAS_SETWINDOWFLOATING
     ImGui_ImplGlfw_SetWindowFloating(vd->Window);
 #endif
 #ifdef _WIN32

docs/CHANGELOG.txt

@@ -94,6 +94,12 @@ Other Changes:
 - Backends: Vulkan: added ImGui_ImplVulkan_CreateMainPipeline() to recreate pipeline
   without reinitializing backend. (#8110, #8111) [@SuperRonan]
 
+Docking+Viewports Branch:
+
+- Backends: GLFW: improve multi-viewport behavior in tiling WMs on X11.
+  Note: using GLFW backend on Linux/BSD etc. requires linking with `-lX11`.
+  (#8884, #8474, #8289) [@Ikos3k, @Madman10K]
+
 
 -----------------------------------------------------------------------
  VERSION 1.92.2b (Released 2025-08-13)

examples/example_glfw_opengl2/Makefile

@@ -21,6 +21,7 @@ SOURCES += $(IMGUI_DIR)/imgui.cpp $(IMGUI_DIR)/imgui_demo.cpp $(IMGUI_DIR)/imgui
 SOURCES += $(IMGUI_DIR)/backends/imgui_impl_glfw.cpp $(IMGUI_DIR)/backends/imgui_impl_opengl2.cpp
 OBJS = $(addsuffix .o, $(basename $(notdir $(SOURCES))))
 UNAME_S := $(shell uname -s)
+LINUX_GL_LIBS = -lGL
 
 CXXFLAGS = -std=c++11 -I$(IMGUI_DIR) -I$(IMGUI_DIR)/backends
 CXXFLAGS += -g -Wall -Wformat
@@ -32,7 +33,7 @@ LIBS =
 
 ifeq ($(UNAME_S), Linux) #LINUX
 	ECHO_MESSAGE = "Linux"
-	LIBS += -lGL `pkg-config --static --libs glfw3`
+	LIBS += $(LINUX_GL_LIBS) -lX11 `pkg-config --static --libs glfw3`
 
 	CXXFLAGS += `pkg-config --cflags glfw3`
 	CFLAGS = $(CXXFLAGS)

examples/example_glfw_vulkan/CMakeLists.txt

@@ -36,6 +36,7 @@ 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) `pkg-config --static --libs glfw3 vulkan`
+	LIBS += $(LINUX_GL_LIBS) -lX11 `pkg-config --static --libs glfw3 vulkan`
 
 	CXXFLAGS += `pkg-config --cflags glfw3 vulkan`
 	CFLAGS = $(CXXFLAGS)