fontsizescrollchanger.cpp

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/**********************************************************************
 * LeechCraft - modular cross-platform feature rich internet client.
 * Copyright (C) 2006-2014  Georg Rudoy
 *
 * Distributed under the Boost Software License, Version 1.0.
 * (See accompanying file LICENSE or copy at https://www.boost.org/LICENSE_1_0.txt)
 **********************************************************************/
 
#include "fontsizescrollchanger.h"
#include <QWidget>
#include <QWheelEvent>
#include <util/sll/lambdaeventfilter.h>
#include <util/sll/visitor.h>
 
namespace LC::Util
{
    namespace
    {
        auto AddSteps (int size, int steps)
        {
            constexpr auto minFontSize = 6;
            return std::max (minFontSize, size + steps);
        }
 
        auto AddSteps (QFont font, int steps)
        {
            if (const auto pts = font.pointSize (); pts > 0)
                font.setPointSize (AddSteps (pts, steps));
            else if (const auto pxs = font.pixelSize (); pxs > 0)
                font.setPixelSize (AddSteps (pxs, steps));
            return font;
        }
    }
 
    void InstallFontSizeChanger (QWidget& widget, const FontSizeChangerParams& params)
    {
        widget.installEventFilter (Util::MakeLambdaEventFilter<QEvent::Wheel> ([params] (QWheelEvent *e)
                {
                    if (!(e->modifiers () & Qt::ControlModifier))
                        return false;
 
                    constexpr qreal degreesPerDelta = 1 / 8.;
                    constexpr qreal degreesPerStep = 15.;
 
                    auto degrees = e->angleDelta ().y () * degreesPerDelta;
                    int steps = static_cast<int> (degrees / degreesPerStep);
 
                    Visit (params,
                            [=] (const auto& methods)
                            {
                                const auto newFont = AddSteps (methods.GetView_ (), steps);
                                methods.SetView_ (newFont);
                                if (e->modifiers () & Qt::ShiftModifier)
                                    methods.SetDefault_ (newFont);
                            });
 
                    return true;
                },
                widget));
    }
}