How to integrate RmlUi with my own rendering engine?

You need to implement the RenderInterface abstract class to handle vertices and draw commands, or use a provided backend like OpenGL 3 from the included samples. The README shows a basic example with a custom render interface in main.cpp.

RmlUi vs libRocket, which is better for new projects?

RmlUi is a fork of libRocket with active development, bug fixes, and added features like data binding and enhanced CSS3 support (e.g., flexbox and filters). It's generally the preferred choice for new C++ UI work due to its ongoing improvements.

Can I use RmlUi for a mobile game on Android?

Yes, RmlUi supports Android, but you'll need to handle platform-specific input and rendering, potentially using the SDL backend with touch support or implementing custom interfaces. The library's cross-platform design facilitates this.

How to style basic elements like buttons in RmlUi?

You must define all styles in RCSS files; for instance, the window.rcss example in the README styles an input element with properties like background-color and border, as RmlUi provides no default styling.

Does RmlUi support JavaScript or only C++?

RmlUi uses C++ for logic, but offers an optional Lua scripting plugin for simplified scripting. There's no built-in JavaScript support, keeping the library lightweight and focused on native integration.

What's the performance impact of using data binding in RmlUi?

Data binding is efficient as it synchronizes data automatically, but complex documents with many bindings or frequent updates can affect performance. The library's lightweight design helps mitigate this, but profiling is recommended for intensive use.

Open-Awesome

RmlUi

MITC++6.2

A lightweight C++ UI library that renders HTML/CSS-like documents for games and applications, with full control over rendering and input.

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4.2k stars434 forks0 contributors

What is RmlUi?

RmlUi is a C++ user interface library that renders HTML and CSS-like documents to create dynamic interfaces for games and applications. It solves the need for a performant, customizable UI solution that integrates directly into C++ projects without relying on a full web browser engine. Developers can style and layout interfaces using familiar web standards while maintaining full control over rendering and input.

Target Audience

C++ developers building games, real-time applications, or tools who need a lightweight, embeddable UI library with HTML/CSS-like styling and data binding capabilities.

Value Proposition

RmlUi offers a unique blend of web standards compliance and native C++ performance, allowing developers to create rich interfaces without the overhead of a browser engine. Its extensible architecture and full control over the render loop make it ideal for integration into existing game engines and applications.

Overview

RmlUi - The HTML/CSS User Interface library evolved

Use Cases

Best For

Creating in-game menus and HUDs with HTML/CSS-like styling
Building tool interfaces for game development or asset pipelines
Developing cross-platform applications with custom rendering backends
Implementing data-driven UIs with real-time data binding
Adding UI to embedded systems or consoles where lightweight libraries are essential
Prototyping interfaces quickly using web design skills in a C++ environment

Not Ideal For

Projects requiring full HTML5/CSS3 compliance for complex, web-like interfaces with advanced scripting
Teams wanting pre-styled, drop-in UI components without extensive custom CSS authoring
Applications deployed as web apps or needing server-side rendering, as RmlUi is strictly for embedded C++ runtimes
Developers seeking a UI library with out-of-the-box support for all graphics APIs without backend limitations

Pros & Cons

Pros

Lightweight Layout Engine

Generates vertices, indices, and draw commands for custom rendering, avoiding heavyweight browser engines and keeping performance high for real-time applications like games.

Extensible Architecture

Allows plugging in custom renderers, font engines, and file systems, with optional Lua scripting support, making it adaptable to existing C++ projects.

Data Binding Support

Synchronizes application data with UI elements using a model-view-controller pattern, enabling dynamic interfaces without manual updates, as shown in the hello_world example.

Cross-Platform Compatibility

Runs on multiple platforms including Windows, Linux, macOS, Android, iOS, and consoles like Switch, with backends for common renderers like OpenGL and Vulkan.

Cons

Partial Standards Compliance

Does not aim for full CSS/HTML compliance to prioritize lightness, which means missing some web features and requiring adjustments for developers expecting browser-like behavior.

Complex Initial Integration

Requires implementing render and system interfaces or integrating backends, which can be time-consuming, especially for custom engines without pre-built support.

No Built-in Styling

Defines no internal styles, forcing developers to write all RCSS from scratch for basic elements like inputs, as noted in the example where rml.rcss must be included for proper layout.

Backend Feature Gaps

Some renderers, such as Vulkan, lack support for advanced features like clip masks and filters, limiting functionality depending on the chosen graphics API.

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