Using ImGui Docking Branch with rlImGui

If you want to use the Docking Features from Dear ImGui's docking branch with rlImGui, it is very easy to setup.

https://github.com/ocornut/imgui/issues/2109

First you must be sure that you are building with the docking tree of the ImGui Source code.

https://github.com/ocornut/imgui/tree/docking

Use this code in place of the regular ImGui source when building rlImGui.

Next, you need to enable docking support (it is off by default).

Inside rlImGui.cpp, find the void SetupRLImGui(bool dark) function.

Add this call during the ImGuiIO setup

io.ConfigFlags |= ImGuiConfigFlags_DockingEnable; // Enable Docking

From there docking will be enabled in all ImGui windows.

If you wish to enable docking to the viewport you will need to call ImGui::DockSpaceOverViewport(); after BeginRLImGui();

If you wish to have an ImGUi Menu bar and docking for something like an editor, please see the code bellow.

https://gist.github.com/JeffM2501/4c3a7e8a85302f743f8bd9dc1aae00ae

int main(int argc, char* argv[])
{
    // Initialization
    //--------------------------------------------------------------------------------------
    int screenWidth = 1900;
    int screenHeight = 900;

    SetConfigFlags(FLAG_MSAA_4X_HINT | FLAG_VSYNC_HINT | FLAG_WINDOW_RESIZABLE);
    InitWindow(screenWidth, screenHeight, "raylib [ImGui] example - ImGui Demo");
    SetTargetFPS(144);
    SetupRLImGui(true);

    // setup a background texture
    Image img = GenImageChecked(64, 64, 16, 16, DARKGRAY, GRAY);
    Texture bg = LoadTextureFromImage(img);
    UnloadImage(img);

    // flag so we can quit the game from the file menu
    bool quit = false;
    // Main game loop
    while (!WindowShouldClose() && !quit)    // Detect window close button or ESC key
    {
        BeginDrawing();
        ClearBackground(DARKGRAY);
        // fill the background with something interesting
        DrawTextureRec(bg, Rectangle{ 0, 0, float(GetScreenWidth()), float(GetScreenHeight()) }, Vector2Zero(), WHITE);
        DrawRectanglePro(Rectangle{ GetScreenWidth() * 0.5f, GetScreenHeight() * 0.5f,200,200 }, Vector2{ 100,100 }, float(GetTime()) * 45, ColorAlpha(RED,0.75f));
        // start the GUI
        BeginRLImGui();
        // create an ImGui window that covers the entire viewport, so that we can have a menu bar at the top of the applications
        ImGui::SetNextWindowPos(ImVec2(0, 0));                                                  // always at the window origin
        ImGui::SetNextWindowSize(ImVec2(float(GetScreenWidth()), float(GetScreenHeight())));    // always at the window size

        ImGuiWindowFlags windowFlags = ImGuiWindowFlags_NoBringToFrontOnFocus |                 // we just want to use this window as a host for the menubar and docking
            ImGuiWindowFlags_NoNavFocus |                                                      // so turn off everything that would make it act like a window
            ImGuiWindowFlags_NoDocking |
            ImGuiWindowFlags_NoTitleBar |
            ImGuiWindowFlags_NoResize |
            ImGuiWindowFlags_NoMove |
            ImGuiWindowFlags_NoCollapse |
            ImGuiWindowFlags_MenuBar |
            ImGuiWindowFlags_NoBackground;                                                      // we want our game content to show through this window, so turn off the background.
        ImGui::PushStyleVar(ImGuiStyleVar_WindowPadding, ImVec2(0, 0));                          // we don't want any padding for windows docked to this window frame
        bool show = (ImGui::Begin("Main", NULL, windowFlags));                                   // show the "window"
        ImGui::PopStyleVar();                                                                    // restore the style so inner windows have fames
        // create a docking space inside our inner window that lets prevents anything from docking in the central node (so we can see our game content)
        ImGui::DockSpace(ImGui::GetID("Dockspace"), ImVec2(0.0f, 0.0f),  ImGuiDockNodeFlags_PassthruCentralNode);
        if (show)
        {
            // Do a menu bar with an exit menu
            if (ImGui::BeginMenuBar())
            {
                if (ImGui::BeginMenu("File"))
                {
                    if (ImGui::MenuItem("Exit"))
                        quit = true;

                    ImGui::EndMenu();
                }
                ImGui::EndMenuBar();
            }
        }
        ImGui::End();
        // show any other windows that we want to be dockable
        ImGui::ShowDemoWindow(NULL);

        // end ImGui
        EndRLImGui();

        // Finish drawing
        DrawFPS(0, GetScreenHeight() - 20);
        EndDrawing();
        //----------------------------------------------------------------------------------
    }
    ShutdownRLImGui();
    UnloadTexture(bg);
    CloseWindow(); 
    return 0;
}