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/* ScrollVar.h
Copyright (c) 2023 by thewierdnut
Endless Sky is free software: you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option) any later version.
Endless Sky is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with
this program. If not, see <https://www.gnu.org/licenses/>.
*/
#pragma once
#include "Animate.h"
// This class allows you to set a scroll value and provides animation
// interpolation between the old and new values, while clamping the value to a
// suitable range. The Animate methods will return negative values, as they are
// meant to be added as an offset to the draw position.
template<typename T>
class ScrollVar : public Animate<T> {
public:
ScrollVar() = default;
ScrollVar(const T &maxVal, const T &displaySize);
// Set the maximum size of the scroll content.
void SetMaxValue(const T &value);
// Get the maximum size of the scroll content.
const T &MaxValue() const;
// Set the size of the displayable scroll area.
void SetDisplaySize(const T &size);
// Get the size of the displayable scroll area.
const T &DisplaySize() const;
// Returns true if scroll buttons are needed.
bool Scrollable() const;
// Returns true if the value is at the minimum.
bool IsScrollAtMin() const;
// Returns true if the value is at the maximum.
bool IsScrollAtMax() const;
// Modifies the scroll value by dy, then clamps it to a suitable range.
void Scroll(const T &dy, int steps = 5);
double AnimatedScrollFraction() const;
double ScrollFraction() const;
// Sets the scroll value directly, then clamps it to a suitable range.
virtual void Set(const T ¤t, int steps = 5) override;
// Shortcut mathematical operators for convenience.
ScrollVar &operator=(const T &v);
private:
// Makes sure the animation value stays in range.
void Clamp(int steps);
T maxVal{};
T displaySize{};
};
template<typename T>
ScrollVar<T>::ScrollVar(const T &maxVal, const T &displaySize)
: maxVal{maxVal}, displaySize{displaySize}
{
}
template<typename T>
void ScrollVar<T>::SetMaxValue(const T &value)
{
maxVal = value;
Clamp(0);
}
template<typename T>
const T &ScrollVar<T>::MaxValue() const
{
return maxVal;
}
template<typename T>
void ScrollVar<T>::SetDisplaySize(const T &size)
{
displaySize = size;
Clamp(0);
}
template<typename T>
const T &ScrollVar<T>::DisplaySize() const
{
return displaySize;
}
template<typename T>
bool ScrollVar<T>::Scrollable() const
{
return maxVal > displaySize;
}
template<typename T>
bool ScrollVar<T>::IsScrollAtMin() const
{
return this->Value() <= T{};
}
template<typename T>
bool ScrollVar<T>::IsScrollAtMax() const
{
return this->Value() >= maxVal - displaySize;
}
template<typename T>
void ScrollVar<T>::Scroll(const T &dy, int steps)
{
Set(this->Value() + dy, steps);
}
template<typename T>
double ScrollVar<T>::AnimatedScrollFraction() const
{
return static_cast<double>(Animate<T>::AnimatedValue()) / static_cast<double>(maxVal - displaySize);
}
template<typename T>
double ScrollVar<T>::ScrollFraction() const
{
return static_cast<double>(Animate<T>::Value()) / static_cast<double>(maxVal - displaySize);
}
template<typename T>
void ScrollVar<T>::Set(const T ¤t, int steps)
{
Animate<T>::Set(current, steps);
Clamp(steps);
}
template<typename T>
void ScrollVar<T>::Clamp(int steps)
{
int maxScroll = maxVal - displaySize;
if(this->Value() < T{} || maxVal < displaySize)
Animate<T>::Set(T{}, steps);
else if(this->Value() > maxScroll)
Animate<T>::Set(maxScroll, steps);
}
template<typename T>
ScrollVar<T> &ScrollVar<T>::operator=(const T &v)
{
Set(v);
return *this;
}
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