gui_pointer_drag.h

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#pragma once
 
#include <gui_core/gui_id.h>
#include <gui_core/gui_base_types.h>
#include <gui_core/input/gui_input_enums.h>
#include <gui_core/input/gui_input_handler_func.h>
#include <gui_core/input/gui_input_state.h>
 
#include <stdint.h>
 
namespace tachyon
{
 
    class ElementStorage;

    constexpr bool IsDragTravel(int2 delta, int32_t distance) noexcept
    {
        const int64_t dx = delta.x, dy = delta.y;
        return dx * dx + dy * dy >= int64_t(distance) * distance;
    }

    constexpr bool IsDragCancelKey(const InputState& s) noexcept
    {
        return s.lastKey == KeyCode::Escape && s.lastKeyAction == KeyAction::KeyDown;
    }

    struct PointerDrag
    {
        ID           id     = ID::Invalid();      
        MouseButtons button = MouseButtons::None; 
        int2         pressScreen{ 0, 0 };         
        int2         pressLocal{ 0, 0 };          
        bool         dragging = false;            

        bool IsHeld() const noexcept { return id != ID::Invalid(); }
        bool IsPressed(ID element) const noexcept { return id != ID::Invalid() && id == element; }
        bool IsDragging(ID element) const noexcept { return dragging && IsPressed(element); }

        bool Press(const ElementEvent& e, const ElementStorage& storage,
                   MouseButtons button = MouseButtons::Left, bool atOnce = false);

        bool Move(const ElementEvent& e, int32_t distance);

        enum class Ended : uint8_t
        {
            No,     
            Click,  
            Drag    
        };

        Ended Release(const ElementEvent& e);

        bool Cancel(ID element) noexcept;
        void Reset() noexcept { *this = PointerDrag{}; }

        int2 ScreenDelta(const InputState& s) const noexcept { return s.screenPos - pressScreen; }
        int2 LocalDelta(const ElementEvent& e, const ElementStorage& storage) const;
    };

}