13. Topic Type View (IDL)

A Topic Type View displays the Interface Definition Language (IDL) type description for a selected DDS topic in a scrollable, selectable monospace text view. When a topic is not yet discovered, the pane waits and loads the IDL automatically once the topic becomes available.

13.1. Opening a Topic Type View

There are several ways to open a new Topic Type View:

  • Right-click a topic in the Topics Panel , the Logical Panel, or the domain graph and choose Data type IDL view.

  • Use Add → Add Topic Type View (IDL) in the application menu bar.

  • Click the three-dots button in the header of any existing pane, choose Split right or Split down, and select Topic Type View (IDL) to open a new IDL pane alongside the current one, or choose Replace panel to replace the current pane with an IDL view.

13.2. Pane Header Controls

  • The header shows the type name of the topic followed by “(IDL)”.

  • Copy to Clipboard - copies the full IDL text to the clipboard in one click.

  • Help - opens a contextual help panel with usage tips and a link to this documentation page.

  • Maximize Pane / Restore Pane - maximizes/ minimizes the pane; click again to restore the previous layout.

  • Configure Pane - opens the Right-Side Pane Configuration sidebar for this pane.

  • The three-dots button opens the split menu to open a new pane to the right or below.

  • Close Pane - closes the pane.

13.3. Text Area Interactions

  • Select text with the mouse or keyboard.

  • Right-clicking opens a context menu with Copy (copies the selection, or the full IDL if nothing is selected) and Select All.

13.4. ROS 2 Demangling

ROS 2 wraps its type names in a mangled format when publishing over DDS (for example, rosidl_typesupport_fastrtps_cpp::std_msgs::msg::dds_::String_ instead of std_msgs/msg/String). Fast DDS Monitor can reverse this mangling to show the original ROS 2 type name and a clean IDL representation that is directly usable with Fast DDS Gen.

When demangling is active, a badge reading ROS 2 Demangling applied appears in the upper-right corner of the IDL pane to indicate that the displayed IDL is not the raw on-the-wire representation.

Demangling is enabled by default and applies to all IDL panes simultaneously. It can be toggled in two ways:

  • View → Revert ROS 2 Demangling to show the raw representation.

  • View → Perform ROS 2 Demangling to restore the clean representation.

The same setting is also available as a toggle in the DISPLAY section of the right-side configuration panel for any open IDL pane.

13.5. Right-Side Configuration Panel Pro

When the Right-Side Pane Configuration sidebar is open for a Topic Type View it shows five sections:

  • Topic - displays the current topic name, domain number, and resolved type name as read-only labels.

  • Change Topic - select a different domain and topic, then apply with Apply & Reload, which fetches and displays the IDL for the new topic immediately.

  • Display - toggle to enable or disable ROS 2 Demangling for the current pane. This setting applies to all IDL panes at once.

  • Panel Actions - Split right and Split down submenus, each letting you open a new pane alongside the current one.

  • Actions - Select All to select the full IDL text in one click.