There are four interfaces that RmlUi provides to control how it interacts with your application.

Only the system and render interfaces are required to be implemented for all applications. The file interface will use a default implementation using standard library methods unless a custom one is installed first. A default font engine will also be installed, which loads fonts and renders glyphs using the FreeType library, unless the user provides their own.

To install a custom interface, instance your interface and install it with the appropriate Rml::Set*Interface() before you initialise RmlUi.

auto file_interface = std::make_unique<CustomFileInterface>();

/* ... */


/* ... */



Lifetime notice: RmlUi takes non-owning pointers to the interfaces, thus, make sure to keep the interface alive until after the call to Rml::Shutdown(), and clean it up afterwards.