Generated code#

The Slint compiler called by the build system will generate a header file for the root .slint file. This header file will contain a class with the same name as the root component.

This class will have the following public member functions:

  • A create constructor function and a destructor.

  • A show function, which will show the component on the screen. You still need to spin the event loop by slint::run_event_loop() or using the convenience run function in this class to render and react to user input!

  • A hide function, which de-registers the component from the windowing system.

  • A window function that provides access to the slint::Window, to allow for further customization towards the windowing system.

  • A run convenience function, which will show the component and starts the event loop.

  • For each property:

    • A getter get_<property_name> returning the property type.

    • A setter set_<property_name> taking the new value of the property by const reference

  • For each callback:

    • invoke_<callback_name> function which takes the callback argument as parameter and call the callback.

    • on_<callback_name> function which takes a functor as an argument and sets the callback handler for this callback. the functor must accept the type parameter of the callback

  • A global function to access exported global singletons.

The create function creates a new instance of the component, which is wrapped in slint::ComponentHandle. This is a smart pointer that owns the actual instance and keeps it alive as long as at least one slint::ComponentHandle is in scope, similar to std::shared_ptr<T>.

For more complex user interfaces it’s common to supply data in the form of an abstract data model, that’s used with for - in repetitions or ListView elements in the .slint language. All models in C++ are sub-classes of the slint::Model and you can sub-class it yourself. For convenience, the slint::VectorModel provides an implementation that’s backed by a std::vector<T>.


Let’s assume we’ve this code in our .slint file:

component SampleComponent inherits Window {
    in-out property<int> counter;
    in-out property<string> user_name;
    callback hello;
    // ... maybe more elements here

This generates a header with the following contents (edited for documentation purpose)

#include <array>
#include <limits>
#include <slint.h>

class SampleComponent {
    /// Constructor function
    inline auto create () -> slint::ComponentHandle<MainWindow>;
    /// Destructor
    inline ~SampleComponent ();

    /// Show this component, and runs the event loop
    inline void run () const;

    /// Show the window that renders this component. Call `slint::run_event_loop()`
    /// to continuously render the contents and react to user input.
    inline void show () const;

    /// Hide the window that renders this component.
    inline void hide () const;

    /// Getter for the `counter` property
    inline int get_counter () const;
    /// Setter for the `counter` property
    inline void set_counter (const int &value) const;

    /// Getter for the `user_name` property
    inline slint::SharedString get_user_name () const;
    /// Setter for the `user_name` property
    inline void set_user_name (const slint::SharedString &value) const;

    /// Call this function to call the `hello` callback
    inline void invoke_hello () const;
    /// Sets the callback handler for the `hello` callback.
    template<typename Functor> inline void on_hello (Functor && callback_handler) const;

    /// Returns a reference to a global singleton that's exported.
    /// **Note:** Only globals that are exported or re-exported from the main .slint file will
    /// be exposed in the API
    inline template<typename T>
    const T &global() const;

    /// private fields omitted

Global Singletons#

You can declare globally available singletons in your .slint files. If exported, these singletons are available via the global() getter function on the generated C++ class. Each global singleton maps to a class iwith getter/setter functions for properties and callbacks, similar to API that’s created for your .slint component.

For example the following .slint markup defines a global Logic singleton that’s also exported:

export global Logic {
    callback to_uppercase(string) -> string;

Assuming this global is used together with the SampleComponent from the previous section, you can access Logic like this:

    auto app = SampleComponent::create();
    // ...
    app->global<Logic>().on_to_uppercase([](SharedString str) -> SharedString {
        std::string arg(str);
        std::transform(arg.begin(), arg.end(), arg.begin(), toupper);
        return SharedString(arg);