14.1.850. tablet_qt/widgets/verticalscrollarea.h

/*
    Copyright (C) 2012-2019 Rudolf Cardinal (rudolf@pobox.com).

    This file is part of CamCOPS.

    CamCOPS 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.

    CamCOPS 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 CamCOPS. If not, see <http://www.gnu.org/licenses/>.
*/

#pragma once

#include <QScrollArea>
#include <QSize>
class QGestureEvent;
class QSwipeGesture;

// http://forum.qt.io/topic/13374/solved-qscrollarea-vertical-scroll-only/4


class VerticalScrollArea : public QScrollArea
{
    // Contains objects in a vertical scroll area.
    //
    // - Inheritance: QScrollArea : QAbstractScrollArea : QFrame : QWidget
    //
    // - Note that it *contains* a QWidget, named 'qt_scrollarea_viewport',
    //   which has the user-inserted widget as its child. This has the same
    //   implications with respect to height-for-width (and height generally?)
    //   as for BaseWidget (q.v.).
    //
    //   - Internally, this is "QWidget* viewport". However, it is in the
    //     private class, accessed via the standard Qt private pointer, so
    //     inaccessible directly -- but accessible via
    //     QAbstractScrollArea::viewport().

    Q_OBJECT
public:

    // Constructor
    explicit VerticalScrollArea(QWidget* parent = nullptr);

    // Standard Qt widget overrides.
    virtual bool event(QEvent* event) override;
    virtual bool eventFilter(QObject* o, QEvent* e) override;
    virtual QSize sizeHint() const override;
    virtual void resizeEvent(QResizeEvent* event) override;

    // Sets the widget to be shown in the scroll area.
    void setWidget(QWidget* widget);  // hides parent version of this function

protected:

    // Called when our child widget resizes, via eventFilter().
    // Sets min width and min/max height. Updates our geometry.
    // We use this code plus the Expanding policy.
    void resetSizeLimits();

    // Handler for gestures, including swipe gestures.
    // (Unused if TOUCHSCROLL_SCROLLER is defined.)
    bool gestureEvent(QGestureEvent* event);

    // Handler for swipe gestures.
    // (Unused if TOUCHSCROLL_SCROLLER is defined.)
    void swipeTriggered(QSwipeGesture* gesture);

protected:
    int m_last_widget_width;  // Last widget width we were told about. Set in resetSizeLimits().
    int m_reentry_depth;  // Used during resize events to prevent infinite recursion.
    QSize m_widget_size_back_1;  // 1-back size of our owned widget
    QSize m_widget_size_back_2;  // 2-back size of our owned widget
};