class mola::MolaVizImGuiCore

Overview

Core rendering and state-management logic for the Dear ImGui MOLA viz backend.

Implements VizInterface so it can be used anywhere a VizInterface::Ptr is expected without going through the full MolaVizImGui MOLA module.

Two operating modes:

Host mode (MolaVizImGui): a companion class creates a GLFW window and ImGui context on a dedicated thread and calls render_frame() each frame.
Embed mode : the caller already owns the GLFW window and ImGui context. After calling init_for_embed() once (GL context current, no ImGui frame open), the caller invokes spin_one_frame() each frame between ImGui::NewFrame() and ImGui::Render(). The 3-D background scene is NOT rendered by the core in this mode; the caller renders it via its own CImGuiSceneView using the scene returned by get_background_scene().

#include <MolaVizImGuiCore.h>

class MolaVizImGuiCore:
    public mola::VizInterface,
    public mrpt::system::COutputLogger
{
public:
    // typedefs

    typedef std::function<void(const mrpt::rtti::CObject::Ptr&, void*subWinHandle, const window_name_t&parentWin, const std::string&subWindowTitle, MolaVizImGuiCore*instance, const mrpt::containers::yaml*extra_parameters)> update_handler_t;
    typedef std::string class_name_t;
    typedef std::string window_name_t;
    typedef std::string subwindow_name_t;
    typedef std::vector<std::function<void()>> task_queue_t;

    // structs

    struct DecayingCloud;
    struct PerWindowData;
    struct SubWindowState;

    // fields

    double console_text_font_size_ = 13.0;
    unsigned int max_console_lines_ = 12;
    bool show_rgbd_as_point_cloud_ = false;
    double assumed_sensor_rate_hz_ = 10.0;
    int target_fps_ = 60;
    std::string imgui_app_name_ = "default";
    static const window_name_t DEFAULT_WINDOW_NAME = "main";
    std::map<window_name_t, PerWindowData> windows_;
    task_queue_t guiThreadPendingTasks_;
    std::mutex guiThreadPendingTasksMtx_;
    std::map<window_name_t, std::string> imgui_ini_paths_;

    // construction

    MolaVizImGuiCore();
    MolaVizImGuiCore(const MolaVizImGuiCore&);
    MolaVizImGuiCore(MolaVizImGuiCore&&);

    // methods

    void register_gui_cleanup(const std::function<void()>& cleanup);
    void run_registered_cleanups();

    static void register_gui_handler(
        const class_name_t& name,
        const update_handler_t& handler
        );

    void init_for_embed(const window_name_t& name = DEFAULT_WINDOW_NAME);
    void shutdown_for_embed();

    PerWindowData& init_window(
        const window_name_t& name,
        GLFWwindow* win
        );

    void spin_one_frame(const window_name_t& name = DEFAULT_WINDOW_NAME);
    void render_frame(const window_name_t& name, PerWindowData& wd);
    std::shared_ptr<mrpt::opengl::COpenGLScene> get_background_scene(const window_name_t& name = DEFAULT_WINDOW_NAME);
    std::mutex* get_background_scene_mutex(const window_name_t& name = DEFAULT_WINDOW_NAME);
    static std::shared_ptr<MolaVizImGuiCore> make_for_embed();
    virtual const std::string& gui_backend() const;
    virtual std::future<void> create_subwindow_from_description(const mola::gui::WindowDescription& desc, const std::string& parentWindow = DEFAULT_WINDOW_NAME);
    virtual std::future<void> enqueue_custom_gui_code(const std::function<void()>& userCode);

    virtual void* get_subwindow_handle(
        const std::string& subWindowTitle,
        const std::string& parentWindow = DEFAULT_WINDOW_NAME
        );

    virtual std::future<std::optional<std::string>> open_file_dialog(
        const std::string& title,
        bool save,
        const std::vector<std::pair<std::string, std::string>>& filters = {},
        const std::string& default_path = "",
        const std::string& parentWindow = DEFAULT_WINDOW_NAME
        );

    virtual std::future<void> set_menu_bar(const mola::gui::MenuBar& bar, const std::string& parentWindow = DEFAULT_WINDOW_NAME);

    virtual std::future<bool> update_3d_object(
        const std::string& objName,
        const std::shared_ptr<mrpt::opengl::CSetOfObjects>& obj,
        const std::string& viewportName = "main",
        const std::string& parentWindow = DEFAULT_WINDOW_NAME
        );

    virtual std::future<bool> insert_point_cloud_with_decay(
        const std::shared_ptr<mrpt::opengl::CPointCloudColoured>& cloud,
        double decay_time_seconds,
        const std::string& viewportName = "main",
        const std::string& parentWindow = DEFAULT_WINDOW_NAME
        );

    virtual std::future<bool> clear_all_point_clouds_with_decay(
        const std::string& viewportName = "main",
        const std::string& parentWindow = DEFAULT_WINDOW_NAME
        );

    virtual std::future<bool> update_viewport_look_at(
        const mrpt::math::TPoint3Df& lookAt,
        const std::string& viewportName = "main",
        const std::string& parentWindow = DEFAULT_WINDOW_NAME
        );

    virtual std::future<bool> update_viewport_camera_azimuth(
        double azimuth,
        bool absolute_falseForRelative = true,
        const std::string& viewportName = "main",
        const std::string& parentWindow = DEFAULT_WINDOW_NAME
        );

    virtual std::future<bool> update_viewport_camera_orthographic(
        bool orthographic,
        const std::string& viewportName = "main",
        const std::string& parentWindow = DEFAULT_WINDOW_NAME
        );

    virtual std::future<bool> execute_custom_code_on_background_scene(
        const std::function<void(mrpt::opengl::Scene&)>& userCode,
        const std::string& parentWindow = DEFAULT_WINDOW_NAME
        );

    virtual std::future<bool> subwindow_update_visualization(
        const mrpt::rtti::CObject::Ptr& obj,
        const std::string& subWindowTitle,
        const mrpt::containers::yaml* extra_parameters = nullptr,
        const std::string& parentWindow = DEFAULT_WINDOW_NAME
        );

    virtual std::future<bool> output_console_message(
        const std::string& msg,
        const std::string& parentWindow = DEFAULT_WINDOW_NAME
        );

    virtual std::future<nanogui::Window*> create_subwindow(
        const std::string& title,
        const std::string& parentWindow = DEFAULT_WINDOW_NAME
        );

    virtual std::future<void> enqueue_custom_nanogui_code(const std::function<void()>& userCode);

    virtual std::future<void> subwindow_grid_layout(
        const std::string& subWindowTitle,
        bool orientationVertical,
        int resolution,
        const std::string& parentWindow = DEFAULT_WINDOW_NAME
        );

    virtual std::future<void> subwindow_move_resize(
        const std::string& subWindowTitle,
        const mrpt::math::TPoint2D_<int>& location,
        const mrpt::math::TPoint2D_<int>& size,
        const std::string& parentWindow = DEFAULT_WINDOW_NAME
        );

    MolaVizImGuiCore& operator = (const MolaVizImGuiCore&);
    MolaVizImGuiCore& operator = (MolaVizImGuiCore&&);
    std::string resolve_imgui_ini_path(const window_name_t& windowName) const;
};

Inherited Members

public:
    // typedefs

    typedef std::shared_ptr<VizInterface> Ptr;

    // methods

    virtual std::future<void> create_subwindow_from_description(
        const mola::gui::WindowDescription& desc,
        const std::string& parentWindow = "main"
        ) = 0;

    virtual std::future<void> enqueue_custom_gui_code(const std::function<void()>& userCode) = 0;
    virtual const std::string& gui_backend() const = 0;

    virtual std::future<void> set_menu_bar(
        const mola::gui::MenuBar& bar,
        const std::string& parentWindow = "main"
        ) = 0;

    virtual void* get_subwindow_handle(
        const std::string& subWindowTitle,
        const std::string& parentWindow = "main"
        ) = 0;

    virtual std::future<bool> update_3d_object(
        const std::string& objName,
        const std::shared_ptr<mrpt::opengl::CSetOfObjects>& obj,
        const std::string& viewportName = "main",
        const std::string& parentWindow = "main"
        ) = 0;

    virtual std::future<bool> insert_point_cloud_with_decay(
        const std::shared_ptr<mrpt::opengl::CPointCloudColoured>& cloud,
        double decay_time_seconds,
        const std::string& viewportName = "main",
        const std::string& parentWindow = "main"
        ) = 0;

    virtual std::future<bool> clear_all_point_clouds_with_decay(
        const std::string& viewportName = "main",
        const std::string& parentWindow = "main"
        ) = 0;

    virtual std::future<bool> update_viewport_look_at(
        const mrpt::math::TPoint3Df& lookAt,
        const std::string& viewportName = "main",
        const std::string& parentWindow = "main"
        ) = 0;

    virtual std::future<bool> update_viewport_camera_azimuth(
        double azimuth,
        bool absolute_falseForRelative = true,
        const std::string& viewportName = "main",
        const std::string& parentWindow = "main"
        ) = 0;

    virtual std::future<bool> update_viewport_camera_orthographic(
        bool orthographic,
        const std::string& viewportName = "main",
        const std::string& parentWindow = "main"
        ) = 0;

    virtual std::future<bool> execute_custom_code_on_background_scene(
        const std::function<void(mrpt::opengl::Scene&)>& userCode,
        const std::string& parentWindow = "main"
        ) = 0;

    virtual std::future<bool> subwindow_update_visualization(
        const mrpt::rtti::CObject::Ptr& obj,
        const std::string& subWindowTitle,
        const mrpt::containers::yaml* extra_parameters = nullptr,
        const std::string& parentWindow = "main"
        ) = 0;

    virtual std::future<bool> output_console_message(
        const std::string& msg,
        const std::string& parentWindow = "main"
        ) = 0;

    virtual std::future<std::optional<std::string>> open_file_dialog(
        const std::string& title,
        bool save,
        const std::vector<std::pair<std::string, std::string>>& filters = {},
        const std::string& default_path = "",
        const std::string& parentWindow = "main"
        ) = 0;

    virtual std::future<nanogui::Window*> create_subwindow(
        const std::string& title,
        const std::string& parentWindow = "main"
        ) = 0;

    virtual std::future<void> enqueue_custom_nanogui_code(const std::function<void()>& userCode) = 0;

    virtual std::future<void> subwindow_grid_layout(
        const std::string& subWindowTitle,
        bool orientationVertical,
        int resolution,
        const std::string& parentWindow = "main"
        ) = 0;

    virtual std::future<void> subwindow_move_resize(
        const std::string& subWindowTitle,
        const mrpt::math::TPoint2D_<int>& location,
        const mrpt::math::TPoint2D_<int>& size,
        const std::string& parentWindow = "main"
        ) = 0;

    VizInterface& operator = (const VizInterface&);
    VizInterface& operator = (VizInterface&&);

Fields

std::string imgui_app_name_ = "default"

Identifier used to key the imgui .ini persistence file. Empty string disables persistence. See MolaVizImGui docs.

Methods

void register_gui_cleanup(const std::function<void()>& cleanup)

Register a cleanup callback on this instance. The callback is called (with the GL context current) during shutdown_for_embed() / destruction and should release any GL handles this instance allocated. Multiple callbacks may be registered; they are called in registration order.

void run_registered_cleanups()

Run all cleanup callbacks registered on this instance. Must be called with the GL context current.

void init_for_embed(const window_name_t& name = DEFAULT_WINDOW_NAME)

Embed mode: register a virtual window (no GLFW window) keyed by name. Must be called once per window-name with the GL context current, before spin_one_frame(). Calling twice with the same name is a no-op (returns without overwriting existing sub-windows / sensor windows).

void shutdown_for_embed()

Embed mode: release GL resources held by registered handlers and clear internal scene state. MUST be called by the host while the GL context is still current, before destroying the ImGui/GL context. Safe to call more than once. If the destructor runs without a prior call, a warning is logged (GL state may leak / crash on shutdown).

void spin_one_frame(const window_name_t& name = DEFAULT_WINDOW_NAME)

Embed mode: drain the task queue and render all MOLA sub-windows into the caller’s active ImGui frame. Background 3-D scene rendering is skipped — the caller is responsible for that. Must be called between ImGui::NewFrame() and ImGui::Render().

void render_frame(const window_name_t& name, PerWindowData& wd)

Host mode: full per-frame render for a GLFW-owned window. Calls glfwMakeContextCurrent, begins a new ImGui frame, runs all sub-renderers (background scene, sub-windows, sensor windows, console overlay), and finishes with ImGui::Render + glfwSwapBuffers.

std::shared_ptr<mrpt::opengl::COpenGLScene> get_background_scene(const window_name_t& name = DEFAULT_WINDOW_NAME)

Expose the shared OpenGL scene written to by MOLA observation handlers. An external CImGuiSceneView (embed mode) can render it directly. Returns nullptr if name is not registered.

Thread-safety: must be called from the GUI thread (the same thread that calls spin_one_frame() / render_frame()). Reads of the returned scene contents on the GUI thread must hold get_background_scene_mutex() for the duration of access — VizInterface writers also lock it.

std::mutex* get_background_scene_mutex(const window_name_t& name = DEFAULT_WINDOW_NAME)

Returns the mutex guarding get_background_scene(). Returns nullptr if name is not registered. Same thread-safety note as get_background_scene().

static std::shared_ptr<MolaVizImGuiCore> make_for_embed()

Embed mode: heap-allocate a core and return it as a VizInterface::Ptr. Preferred over constructing on the stack/as a member, because MOLA modules (e.g. mola_lidar_odometry) consume a VizInterface::Ptr and the host must guarantee the instance outlives them. The returned pointer can also be dynamic_pointer_cast<MolaVizImGuiCore> to reach embed-specific APIs.

Caller must still invoke init_for_embed() once the GL context is current, and shutdown_for_embed() while it is still current.

virtual const std::string& gui_backend() const

Returns a short identifier string for the active GUI backend.

Clients may use this to conditionally tune their GUIs - for example to choose between an Entypo icon (nanogui) and a FontAwesome codepoint (ImGui), or to skip features not yet supported on a given backend.

Canonical values are provided as static constants below: VizInterface::BACKEND_NANOGUI → “nanogui” VizInterface::BACKEND_IMGUI → “imgui”

Comparison example:

if (visualizer_->gui_backend() == VizInterface::BACKEND_IMGUI) { ... }

The method is pure virtual so each concrete backend is forced to declare its identity explicitly. It is noexcept and const so it is safe to call from any context, including hot loops.

virtual std::future<void> create_subwindow_from_description(
    const mola::gui::WindowDescription& desc,
    const std::string& parentWindow = DEFAULT_WINDOW_NAME
    )

Creates a sub-window described by a GuiWidgetDescription.

The description carries the window title, initial position/size hints, tab structure, and all widget definitions including their initial values and on_change callbacks.

The returned future resolves once the window has been created in the GUI thread and all widgets are live. Callers that need to know when construction is complete should call .get() on the future.

Position and size in the description are treated as first-use hints :

nanogui backend : applied unconditionally via setPosition/setFixedWidth.
ImGui backend : passed as ImGuiCond_FirstUseEver, so the dock manager and imgui.ini take over from the second run.

Label text is updated at any time and from any thread by calling LiveString::set() on the LiveString instances embedded in the description. The backend polls them on each frame / spinOnce tick.

Parameters:

desc	Full window and widget description.
parentWindow	Name of the parent host window (default: “main”).

Returns:

future<void> that resolves when the window is live.

virtual std::future<void> enqueue_custom_gui_code(const std::function<void()>& userCode)

Enqueues arbitrary code to run on the GUI thread at the next available opportunity.

Use this for any GUI-thread work that is not covered by the widget description API: e.g. updating widget enable/disable state, changing slider ranges at runtime, or interacting with toolkit-specific objects via a cast of the opaque handle returned by get_subwindow_handle().

The callable is executed in the GUI thread; do not call blocking operations inside it.

This replaces the deprecated enqueue_custom_nanogui_code().

virtual void* get_subwindow_handle(
    const std::string& subWindowTitle,
    const std::string& parentWindow = DEFAULT_WINDOW_NAME
    )

Returns an opaque handle to a previously created sub-window.

The handle type depends on the backend:

MolaViz (nanogui) : cast to nanogui::Window*
MolaVizImGui : the handle is not meaningful as a pointer; use enqueue_custom_gui_code() with ImGui calls keyed on the window title instead.

Returns nullptr if the window does not exist yet or the backend does not support retained window objects.

This is an intentional “escape hatch” for toolkit-specific code that cannot be expressed through the description API. Prefer enqueue_custom_gui_code() over casting this pointer wherever possible, as that keeps the calling module’s cpp file free of GUI toolkit headers.

virtual std::future<std::optional<std::string>> open_file_dialog(
    const std::string& title,
    bool save,
    const std::vector<std::pair<std::string, std::string>>& filters = {},
    const std::string& default_path = "",
    const std::string& parentWindow = DEFAULT_WINDOW_NAME
    )

Opens a modal file-picker dialog on the GUI thread.

The call is non-blocking: it enqueues the dialog to open on the GUI thread and returns a future that resolves when the user dismisses it.

Parameters:

title	Dialog window title, e.g. “Open point cloud”.
save	true → “Save as” dialog (prompts before overwrite). false → “Open” dialog (validates file exists).
filters	List of {description, comma-separated-extensions} pairs. Example: {{“LAS files”,”las,laz”},{“All files”,”*”}} Pass an empty vector to show all files.
default_path	Initial directory or full path suggestion. Empty string means the backend’s default (usually the current working directory).
parentWindow	Host window name.

Returns:

future resolving to the chosen absolute path, or std::nullopt if the user cancelled.

virtual std::future<void> set_menu_bar(
    const mola::gui::MenuBar& bar,
    const std::string& parentWindow = DEFAULT_WINDOW_NAME
    )

Installs or replaces the menu bar of a parent window.

Menu bars are a first-class feature of the Dear ImGui docking branch (ImGui::BeginMainMenuBar / BeginMenuBar). The nanogui backend has no native equivalent and provides a no-op stub that resolves the future immediately without rendering anything. Callers should guard with gui_backend() if the menus are essential to their workflow:

if (visualizer_->gui_backend() == VizInterface::BACKEND_IMGUI)
    visualizer_->set_menu_bar(bar);

Parameters:

bar	Full menu bar description.
parentWindow	Host window whose menu bar is replaced.

Returns:

future<void> resolving when the menu bar is live.

virtual std::future<bool> update_3d_object(
    const std::string& objName,
    const std::shared_ptr<mrpt::opengl::CSetOfObjects>& obj,
    const std::string& viewportName = "main",
    const std::string& parentWindow = DEFAULT_WINDOW_NAME
    )

Updates or inserts a 3D object in the background scene.

The update is performed in the GUI thread. If the named object already exists, its contents are replaced by copying the shared pointers inside obj.

Parameters:

objName	Name used to identify the object (upsert key).
obj	Object to display.
viewportName	Viewport inside the parent window.
parentWindow	Host window name.

Returns:

future<bool>; resolves to true when executed.

virtual std::future<bool> insert_point_cloud_with_decay(
    const std::shared_ptr<mrpt::opengl::CPointCloudColoured>& cloud,
    double decay_time_seconds,
    const std::string& viewportName = "main",
    const std::string& parentWindow = DEFAULT_WINDOW_NAME
    )

Inserts a temporary point cloud visible for decay_time_seconds.

Parameters:

cloud	Cloud to display.
decay_time_seconds	Lifetime in seconds before the cloud fades out.
viewportName	Target viewport.
parentWindow	Host window name.

Returns:

future<bool> resolving to true when executed.

virtual std::future<bool> clear_all_point_clouds_with_decay(
    const std::string& viewportName = "main",
    const std::string& parentWindow = DEFAULT_WINDOW_NAME
    )

Removes all clouds previously inserted with insert_point_cloud_with_decay().

virtual std::future<bool> update_viewport_look_at(
    const mrpt::math::TPoint3Df& lookAt,
    const std::string& viewportName = "main",
    const std::string& parentWindow = DEFAULT_WINDOW_NAME
    )

Moves the viewport camera look-at point.

virtual std::future<bool> update_viewport_camera_azimuth(
    double azimuth,
    bool absolute_falseForRelative = true,
    const std::string& viewportName = "main",
    const std::string& parentWindow = DEFAULT_WINDOW_NAME
    )

Rotates the viewport camera around the vertical axis.

Parameters:

azimuth	Angle in radians.
absolute_falseForRelative	true → set absolute azimuth; false → add increment to current value.

virtual std::future<bool> update_viewport_camera_orthographic(
    bool orthographic,
    const std::string& viewportName = "main",
    const std::string& parentWindow = DEFAULT_WINDOW_NAME
    )

Switches the viewport camera between perspective and orthographic.

virtual std::future<bool> execute_custom_code_on_background_scene(
    const std::function<void(mrpt::opengl::Scene&)>& userCode,
    const std::string& parentWindow = DEFAULT_WINDOW_NAME
    )

Executes arbitrary user code on the mrpt::opengl::Scene of the background viewport.

Use this to modify viewport properties, add sub-viewports, change background colour, etc. The callable runs in the GUI thread.

This method operates on the mrpt OpenGL scene, not on GUI toolkit widgets, so it is backend-agnostic: both nanogui and ImGui backends embed an mrpt scene in their OpenGL canvas.

virtual std::future<bool> subwindow_update_visualization(
    const mrpt::rtti::CObject::Ptr& obj,
    const std::string& subWindowTitle,
    const mrpt::containers::yaml* extra_parameters = nullptr,
    const std::string& parentWindow = DEFAULT_WINDOW_NAME
    )

Updates a sub-window’s content from an MRPT object.

The correct handler is selected based on the runtime type of obj. Custom handlers can be registered via MolaViz::register_gui_handler().

Returns:

future<bool> resolving to false if no handler exists for the object’s type.

virtual std::future<bool> output_console_message(
    const std::string& msg,
    const std::string& parentWindow = DEFAULT_WINDOW_NAME
    )

Appends a line of text to the on-screen console overlay.

virtual std::future<nanogui::Window*> create_subwindow(
    const std::string& title,
    const std::string& parentWindow = DEFAULT_WINDOW_NAME
    )

Deprecated Use create_subwindow_from_description() instead.

Returns a nanogui::Window* through a future. On non-nanogui backends this returns a future containing nullptr; callers must guard against this. The returned pointer must not be deleted by the caller.

virtual std::future<void> enqueue_custom_nanogui_code(const std::function<void()>& userCode)

Deprecated Use enqueue_custom_gui_code() instead.

Retained for source compatibility; both names dispatch to the same internal queue.

virtual std::future<void> subwindow_grid_layout(
    const std::string& subWindowTitle,
    bool orientationVertical,
    int resolution,
    const std::string& parentWindow = DEFAULT_WINDOW_NAME
    )

Deprecated Encode layout in WindowDescription::tabs instead.

On ImGui backends this is a no-op (ImGui manages layout automatically).

virtual std::future<void> subwindow_move_resize(
    const std::string& subWindowTitle,
    const mrpt::math::TPoint2D_<int>& location,
    const mrpt::math::TPoint2D_<int>& size,
    const std::string& parentWindow = DEFAULT_WINDOW_NAME
    )

Deprecated Encode position and size in WindowDescription instead.

On ImGui backends position/size are first-use hints only; the dock manager overrides them freely.