src/settings.h

#ifndef SETTINGS_H
#define SETTINGS_H
#include <QSettings>
#include "settingdefs.h"

// SettingType - get type of setting by enumerator
template<Setting>
struct SettingInfo{};

#define SETTING(NAME, DEFVALUE) \
	template<> \
	struct SettingInfo<Setting::NAME> \
	{ \
		using type = decltype((DEFVALUE)); \
		static constexpr char name[] = #NAME; \
		static const auto& defaultValue() { \
			static const auto value = DEFVALUE; \
			return value; \
		}; \
	};
#include "settingdefs.h"
#undef SETTING

template<Setting X>
using SettingType_t = typename SettingInfo<X>::type;
static_assert(std::is_same_v<SettingType_t<Setting::DrawAxes>, bool>);

template<Setting X>
const char* settingName = SettingInfo<X>::name;

template<Setting X>
inline auto settingDefaultValue()
{
	return SettingInfo<X>::defaultValue();
}

// get() - get setting by enumerator
template<Setting X>
inline SettingType_t<X> setting()
{
	static const QVariant defvariant = QVariant::fromValue(settingDefaultValue<X>());
	const QVariant var = QSettings{}.value(settingName<X>, defvariant);
	return var.value<SettingType_t<X>>();
}

// setSetting() - set value of setting
template<Setting X>
inline void setSetting(const SettingType_t<X>& value)
{
	if (value == settingDefaultValue<X>()) {
		QSettings{}.remove(settingName<X>);
	}
	else {
		QSettings{}.setValue(settingName<X>, QVariant::fromValue(value));
	}
}

#endif // SETTINGS_H