Merge branch 'viewport' into docking

# Conflicts:
#	examples/example_glfw_opengl2/main.cpp
#	examples/example_glfw_opengl3/main.cpp
#	examples/example_glfw_vulkan/main.cpp
#	examples/example_sdl_opengl2/main.cpp
#	examples/example_sdl_opengl3/main.cpp
#	examples/example_sdl_vulkan/main.cpp
#	examples/example_win32_directx10/main.cpp
#	examples/example_win32_directx11/main.cpp
#	examples/example_win32_directx12/main.cpp
#	examples/example_win32_directx9/main.cpp

examples/example_sdl_opengl2/main.cpp

@@ -40,6 +40,9 @@ int main(int, char**)
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;       // Enable Keyboard Controls
     io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;           // Enable Docking
+    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;         // Enable Multi-Viewport / Platform Windows
+    //io.ConfigFlags |= ImGuiConfigFlags_ViewportsNoTaskBarIcons;
+    //io.ConfigFlags |= ImGuiConfigFlags_ViewportsNoMerge;
 
     ImGui_ImplSDL2_InitForOpenGL(window, gl_context);
     ImGui_ImplOpenGL2_Init();

examples/example_win32_directx12/main.cpp

@@ -292,7 +292,7 @@ int main(int, char**)
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;       // Enable Keyboard Controls
     io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;           // Enable Docking
-    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;         // Enable Multi-Viewport / Platform Windows
+    //io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;       // Enable Multi-Viewport / Platform Windows (FIXME: Currently broken in DX12 back-end, need some work!)
     //io.ConfigFlags |= ImGuiConfigFlags_ViewportsNoTaskBarIcons;
     //io.ConfigFlags |= ImGuiConfigFlags_ViewportsNoMerge;
 

examples/example_win32_directx9/main.cpp

@@ -81,6 +81,9 @@ int main(int, char**)
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;       // Enable Keyboard Controls
     io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;           // Enable Docking
+    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;         // Enable Multi-Viewport / Platform Windows
+    //io.ConfigFlags |= ImGuiConfigFlags_ViewportsNoTaskBarIcons;
+    //io.ConfigFlags |= ImGuiConfigFlags_ViewportsNoMerge;
 
     ImGui_ImplWin32_Init(hwnd);
     ImGui_ImplDX9_Init(g_pd3dDevice);

examples/imgui_impl_glfw.cpp

@@ -45,6 +45,7 @@
 #define GLFW_HAS_WINDOW_ALPHA       (GLFW_VERSION_MAJOR * 1000 + GLFW_VERSION_MINOR * 100 >= 3300) // 3.3+ glfwSetWindowOpacity
 #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
 
 // Data
 enum GlfwClientApi
@@ -505,8 +506,13 @@ static void ImGui_ImplGlfw_SetWindowTitle(ImGuiViewport* viewport, const char* t
 
 static void ImGui_ImplGlfw_SetWindowFocus(ImGuiViewport* viewport)
 {
+#if GLFW_HAS_FOCUS_WINDOW
     ImGuiViewportDataGlfw* data = (ImGuiViewportDataGlfw*)viewport->PlatformUserData;
     glfwFocusWindow(data->Window);
+#else
+    // FIXME: What are the effect of not having this function? At the moment imgui doesn't actually call SetWindowFocus - we set that up ahead, will answer that question later.
+    (void)viewport;
+#endif
 }
 
 static bool ImGui_ImplGlfw_GetWindowFocus(ImGuiViewport* viewport)

imgui.cpp

@@ -8813,6 +8813,7 @@ static void ImGui::NavUpdateWindowing()
     // Apply final focus
     if (apply_focus_window && (g.NavWindow == NULL || apply_focus_window != g.NavWindow->RootWindowDockStop))
     {
+        ImGuiViewport* previous_viewport = g.NavWindow ? g.NavWindow->Viewport : NULL;
         g.NavDisableHighlight = false;
         g.NavDisableMouseHover = true;
         apply_focus_window = NavRestoreLastChildNavWindow(apply_focus_window);
@@ -8824,6 +8825,10 @@ static void ImGui::NavUpdateWindowing()
         // If the window only has a menu layer, select it directly
         if (apply_focus_window->DC.NavLayerActiveMask == (1 << 1))
             g.NavLayer = 1;
+
+        // Request OS level focus
+        if (apply_focus_window->Viewport != previous_viewport && g.PlatformIO.Platform_SetWindowFocus)
+            g.PlatformIO.Platform_SetWindowFocus(apply_focus_window->Viewport);
     }
     if (apply_focus_window)
         g.NavWindowingTarget = NULL;