BackendGuiSFML.hpp

//
// TGUI - Texus' Graphical User Interface
// Copyright (C) 2012-2025 Bruno Van de Velde (vdv_b@tgui.eu)
//
// This software is provided 'as-is', without any express or implied warranty.
// In no event will the authors be held liable for any damages arising from the use of this software.
//
// Permission is granted to anyone to use this software for any purpose,
// including commercial applications, and to alter it and redistribute it freely,
// subject to the following restrictions:
//
// 1. The origin of this software must not be misrepresented;
//    you must not claim that you wrote the original software.
//    If you use this software in a product, an acknowledgment
//    in the product documentation would be appreciated but is not required.
//
// 2. Altered source versions must be plainly marked as such,
//    and must not be misrepresented as being the original software.
//
// 3. This notice may not be removed or altered from any source distribution.
//
 
#ifndef TGUI_BACKEND_GUI_SFML_HPP
#define TGUI_BACKEND_GUI_SFML_HPP
 
#include <TGUI/Config.hpp>
#if !TGUI_BUILD_AS_CXX_MODULE
    #include <TGUI/Backend/Window/BackendGui.hpp>
#endif
 
#include <SFML/Window.hpp>

 
TGUI_MODULE_EXPORT namespace tgui
{
 
    class TGUI_API BackendGuiSFML : public BackendGui
    {
    public:

        BackendGuiSFML();

        ~BackendGuiSFML();

        bool handleEvent(sf::Event event);
        using BackendGui::handleEvent;
 
#if SFML_VERSION_MAJOR >= 3
        template <typename... Ts>
        void handleWindowEvents(Ts&&... handlers)
        {
            if (!m_window)
                return;
 
            m_window->handleEvents([this,&handlers...](auto&& event) {
                using EventType = decltype(event);
 
                // We can't properly detect whether the handlers are valid (e.g. when using an invalid event type),
                // but we can do some tests that will give errors on handlers that are wrong but almost correct.
                static_assert(!std::disjunction_v<std::is_invocable_r<bool, Ts, EventType, bool>...>, "Handler for handleWindowEvents can't have both an extra bool argument and a bool return type");
 
                // If any of the handlers return a bool then they will be executed before the event is passed to the gui.
                // The returned boolean then decides whether the gui should still process the event or not.
                // Only one of the handlers should match at most, but letting the compiler figure out which handler to
                // call by creating an overload set is tricky because only handlers with a bool returns should be called here.
                auto callIfMatchesAndReturnsBool = [&event](auto&& handler)
                {
                    // std::is_invocable_r_v would still return true if the type is convertable to bool, so we use std::invoke_result_t to test the return type
                    using FuncType = decltype(handler);
                    if constexpr (std::is_invocable_v<FuncType, EventType>)
                    {
                        if constexpr (std::is_same_v<std::invoke_result_t<FuncType, EventType>, bool>)
                            return std::invoke(std::forward<FuncType>(handler), std::forward<EventType>(event));
                        else
                        {
                            static_assert(std::is_same_v<std::invoke_result_t<FuncType, EventType>, void>, "Handler for handleWindowEvents must have either 'void' or 'bool' return type");
                            return true;
                        }
                    }
                    else
                        return true;
                };
                const bool passEventToGui = (callIfMatchesAndReturnsBool(std::forward<Ts>(handlers)) && ...);
 
                // Let the gui handle the event
                bool eventHandledByGui = false;
                if (passEventToGui)
                    eventHandledByGui = handleEvent(std::forward<EventType>(event));
 
                // After the gui has handled the events, we call the handlers that return nothing.
                // These handlers can have an optional bool parameter that indicates whether the event was processed by the gui.
                auto callIfMatchesAndReturnsVoid = [&event](auto&& handler, auto&&... extraArgs)
                {
                    using FuncType = decltype(handler);
                    if constexpr (std::is_invocable_v<FuncType, EventType, decltype(extraArgs)...>)
                    {
                        if constexpr (std::is_same_v<std::invoke_result_t<FuncType, EventType, decltype(extraArgs)...>, void>)
                            std::invoke(std::forward<FuncType>(handler), std::forward<EventType>(event), std::forward<decltype(extraArgs)>(extraArgs)...);
                    }
                };
                (callIfMatchesAndReturnsVoid(std::forward<Ts>(handlers)), ...);
                (callIfMatchesAndReturnsVoid(std::forward<Ts>(handlers), eventHandledByGui), ...);
            });
        }
#endif

        void mainLoop(Color clearColor = {240, 240, 240}) override;

        TGUI_NODISCARD bool convertEvent(const sf::Event& eventSFML, Event& eventTGUI);

        sf::Window* getWindow() const;

        void startTextInput(FloatRect inputRect) override;

        void stopTextInput() override;

        void updateTextCursorPosition(FloatRect inputRect, Vector2f caretPos) override;

        TGUI_NODISCARD bool isKeyboardModifierPressed(Event::KeyModifier modifierKey) const override;

    protected:

        void setGuiWindow(sf::Window& window);

        // Updates the view and changes the size of the root container when needed
        void updateContainerSize() override;

    protected:
 
        sf::Window* m_window = nullptr;
 
        bool m_modifierKeySystemPressed = false;
        bool m_modifierKeyControlPressed = false;
        bool m_modifierKeyShiftPressed = false;
        bool m_modifierKeyAltPressed = false;

    };
}

 
#endif // TGUI_BACKEND_GUI_SFML_HPP