91 lines
3.7 KiB
C++
91 lines
3.7 KiB
C++
/***************************************************************************
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* Copyright (c) 2015 Pavel Strakhov <ri@idzaaus.org> *
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* Copyright (c) 2015 Eivind Kvedalen <eivind@kvedalen.name> *
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* *
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* This file is part of the FreeCAD CAx development system. *
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* *
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* This library is free software; you can redistribute it and/or *
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* modify it under the terms of the GNU Library General Public *
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* License as published by the Free Software Foundation; either *
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* version 2 of the License, or (at your option) any later version. *
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* *
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* This library is distributed in the hope that it will be useful, *
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* but WITHOUT ANY WARRANTY; without even the implied warranty of *
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
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* GNU Library General Public License for more details. *
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* *
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* You should have received a copy of the GNU Library General Public *
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* License along with this library; see the file COPYING.LIB. If not, *
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* write to the Free Software Foundation, Inc., 59 Temple Place, *
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* Suite 330, Boston, MA 02111-1307, USA *
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* *
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***************************************************************************/
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/*
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* Based on
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*
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* http://stackoverflow.com/questions/19113532/qgraphicsview-zooming-in-and-out-under-mouse-position-using-mouse-wheel
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*
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* Re-licensed to LGPL after having contacted original author by e-mail.
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*
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*/
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#ifndef GRAPHICSVIEWZOOM_H
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#define GRAPHICSVIEWZOOM_H
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#include <QObject>
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#include <QPointF>
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/*!
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* This class adds ability to zoom QGraphicsView using mouse wheel. The point under cursor
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* remains motionless while it's possible.
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*
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* Note that it becomes not possible when the scene's
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* size is not large enough comparing to the viewport size. QGraphicsView centers the picture
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* when it's smaller than the view. And QGraphicsView's scrolls boundaries don't allow to
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* put any picture point at any viewport position.
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*
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* When the user starts scrolling, this class remembers original scene position and
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* keeps it until scrolling is completed. It's better than getting original scene position at
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* each scrolling step because that approach leads to position errors due to before-mentioned
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* positioning restrictions.
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*
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* When zommed using scroll, this class emits zoomed() signal.
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*
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* Usage:
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*
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* new GraphicsViewZoom(view);
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*
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* The object will be deleted automatically when the view is deleted.
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*
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* You can set keyboard modifiers used for zooming using set_modified(). Zooming will be
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* performed only on exact match of modifiers combination. The default modifier is Ctrl.
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*
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* You can change zoom velocity by calling set_zoom_factor_base().
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* Zoom coefficient is calculated as zoom_factor_base^angle_delta
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* (see QWheelEvent::angleDelta).
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* The default zoom factor base is 1.0015.
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*/
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class QGraphicsView;
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class GraphicsViewZoom : public QObject {
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Q_OBJECT
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public:
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GraphicsViewZoom(QGraphicsView* view);
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void gentle_zoom(double factor);
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void set_modifiers(Qt::KeyboardModifiers modifiers);
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void set_zoom_factor_base(double value);
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private:
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QGraphicsView* _view;
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Qt::KeyboardModifiers _modifiers;
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double _zoom_factor_base;
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QPointF target_scene_pos, target_viewport_pos;
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bool eventFilter(QObject* object, QEvent* event);
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};
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#endif // GRAPHICSVIEWZOOM_H
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