RmlUi

RmlUi is a user interface library that lays out and styles documents the way a web browser does: a document is written in RML (an HTML-like markup) and styled with RCSS (a CSS-like style sheet), and the library handles layout, text, scrolling, forms, animations and events. The acron.rmlui module integrates RmlUi 6 with the engine: a document is rendered by a RmlRegion, which is an ordinary DisplayRegion on a window or an off-screen buffer, and is driven from Python through the element, event and data-binding classes described in this section.

Use RmlUi when the interface is something a web page would describe well: a menu system, a settings screen, a HUD with panels and lists, an in-world terminal. DirectGUI remains the right tool for widgets that live in the scene graph and move with it.

What the integration provides

• RmlRegion – the display region that owns an RmlUi context, keeps it sized to the region, feeds it input and renders it every frame. There is no update task to write.

• RmlContext – loads documents and fonts, owns the data models, answers hit tests.

• RmlDocument and RmlElement – the DOM: show and hide documents, find elements, set classes, attributes, inline styles and inner RML, query geometry, build elements programmatically.

• RmlEvent – delivered to callbacks attached with RmlElement.add_event_listener().

• RmlDataModel – RmlUi’s data binding, backed by Python callables: {{ name }} expressions, data-for lists, data-if conditions and data-event-click handlers that call into your code.

• RmlInputHandler – a data graph node under the mouse watcher that turns the engine’s mouse and keyboard events into RmlUi input.

Documents, style sheets, fonts and images are read through the VirtualFileSystem and resolved against the model path, like any other asset.

Building the module

The module is built when makeacron is given --use-rmlui together with the location of an RmlUi 6 build (--rmlui-incdir and --rmlui-libdir). RmlUi must be built with RMLUI_CUSTOM_RTTI=OFF. On macOS the RmlUi shared libraries are bundled next to the engine’s own.

• Getting Started with RmlUi
• Documents and Elements
• Events
• Data Binding
• Input
• Off-screen Regions and High-DPI Displays
• Layout and Rendering Notes

The samples/rocket-console sample program shows a loading dialog on the main window and an interactive terminal rendered into a texture on a 3D model. The module’s own tests, under tests/rmlui, are short and exercise every class against an off-screen window.