At least on macOS, we need to set the GLFW_FOCUS_ON_SHOW hint (GFLW 3…

….3+) to be able to move freely the new GLFW window. Otherwise, when the GLFW window is created for the new viewport, this one takes the focus and it is not more possible to move it without a second click inside. NOTE: With this code, the main viewport keeps the focus. It is possible to give the focus to the new viewport when the user release the mouse button but that's not related to the problem here.

examples/imgui_impl_glfw.cpp

@@ -46,6 +46,7 @@
 #define GLFW_HAS_PER_MONITOR_DPI    (GLFW_VERSION_MAJOR * 1000 + GLFW_VERSION_MINOR * 100 >= 3300) // 3.3+ glfwGetMonitorContentScale
 #define GLFW_HAS_VULKAN             (GLFW_VERSION_MAJOR * 1000 + GLFW_VERSION_MINOR * 100 >= 3200) // 3.2+ glfwCreateWindowSurface
 #define GLFW_HAS_FOCUS_WINDOW       (GLFW_VERSION_MAJOR * 1000 + GLFW_VERSION_MINOR * 100 >= 3200) // 3.2+ glfwFocusWindow
+#define GLFW_HAS_FOCUS_ON_SHOW      (GLFW_VERSION_MAJOR * 1000 + GLFW_VERSION_MINOR * 100 >= 3300) // 3.3+ GLFW_FOCUS_ON_SHOW
 
 // Data
 enum GlfwClientApi
@@ -378,8 +379,12 @@ static void ImGui_ImplGlfw_CreateWindow(ImGuiViewport* viewport)
     viewport->PlatformUserData = data;
 
     // GLFW 3.2 unfortunately always set focus on glfwCreateWindow() if GLFW_VISIBLE is set, regardless of GLFW_FOCUSED
+    // With GLFW 3.3, the hint GLFW_FOCUS_ON_SHOW fixes this problem
     glfwWindowHint(GLFW_VISIBLE, false);
     glfwWindowHint(GLFW_FOCUSED, false);
+#if GLFW_HAS_FOCUS_ON_SHOW
+    glfwWindowHint(GLFW_FOCUS_ON_SHOW, false);
+#endif
     glfwWindowHint(GLFW_DECORATED, (viewport->Flags & ImGuiViewportFlags_NoDecoration) ? false : true);
 #if GLFW_HAS_WINDOW_TOPMOST
     glfwWindowHint(GLFW_FLOATING, (viewport->Flags & ImGuiViewportFlags_TopMost) ? true : false);