AbsoluteOrRelativeValue.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.
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// 3. This notice may not be removed or altered from any source distribution.
//
 
#ifndef TGUI_ABSOLUTE_OR_RELATIVE_VALUE_HPP
#define TGUI_ABSOLUTE_OR_RELATIVE_VALUE_HPP
 
#include <TGUI/Global.hpp>
#include <TGUI/String.hpp>
 
#include <type_traits>

 
namespace tgui
{
    class TGUI_API AbsoluteOrRelativeValue
    {
    public:

        constexpr AbsoluteOrRelativeValue() = default;

        template <typename T, typename = typename std::enable_if_t<std::is_arithmetic<T>::value, T>>
        constexpr AbsoluteOrRelativeValue(T constant) :
            m_constant    {true},
            m_value       {static_cast<float>(constant)}
        {
        }

        AbsoluteOrRelativeValue(const char* expression) :
            AbsoluteOrRelativeValue{String{expression}}
        {
        }

        AbsoluteOrRelativeValue(const String& expression)
        {
            if (!expression.empty() && (expression.back() == '%'))
            {
                m_constant = false;
                m_ratio    = expression.substr(0, expression.length()-1).toFloat() / 100.f;
            }
            else
            {
                m_constant = true;
                m_value    = expression.substr(0, expression.length()).toFloat();
            }
        }

        TGUI_NODISCARD constexpr float getValue() const
        {
            return m_value;
        }

        TGUI_NODISCARD constexpr float getRatio() const
        {
            return m_ratio;
        }

        TGUI_NODISCARD constexpr bool isConstant() const
        {
            return m_constant;
        }

        constexpr void updateParentSize(float newParentSize)
        {
            if (!m_constant)
            {
                m_parentValue = newParentSize;
                m_value = m_ratio * newParentSize;
            }
        }

        TGUI_NODISCARD String toString() const
        {
            if (m_constant)
                return String::fromNumber(m_value);
            else
                return String::fromNumber(m_ratio * 100) + '%';
        }

    protected:
 
        bool  m_constant     = true;
        float m_value        = 0;
        float m_ratio        = 0;
        float m_parentValue  = 0;
    };

    struct TGUI_API RelativeValue : AbsoluteOrRelativeValue
    {
        explicit constexpr RelativeValue(float ratio)
        {
            m_constant = false;
            m_ratio    = ratio;
        }
    };

 
    // Allow writing 50_percent instead of RelativeValue(0.5) after adding "using namespace tgui::literals::percent;"
    // This can also be used in layouts, where you can replace e.g. the "40%" string with 40_percent to skip string parsing
    inline namespace literals
    {
        inline namespace percent
        {
            constexpr RelativeValue operator""_percent(long double n)
            {
                return RelativeValue{static_cast<float>(n / 100.0L)};
            }
 
            constexpr RelativeValue operator""_percent(unsigned long long n)
            {
                return RelativeValue{static_cast<float>(n) / 100.f};
            }
        }
    }

}

 
#endif // TGUI_ABSOLUTE_OR_RELATIVE_VALUE_HPP