shapetransform.h

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/*
        Copyright 2006-2026 The QElectroTech Team
        This file is part of QElectroTech.
 
        QElectroTech 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 2 of the License, or
        (at your option) any later version.
 
        QElectroTech 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 QElectroTech.  If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef SHAPETRANSFORM_H
#define SHAPETRANSFORM_H
 
#include <QPointF>
#include <QTransform>

struct ShapeTransform
{
        qreal rotation = 0;   // degrees
        qreal skewX = 0;      // degrees
        qreal skewY = 0;      // degrees
        qreal scaleX = 1;
        qreal scaleY = 1;
        QPointF pivot;        // local coordinates; caller decides the default (usually local bbox center)
 
        bool isIdentity() const;
 
        // Rotate+shear+scale about the origin, ignoring pivot -- this is the
        // "linear part" used by compensatedPositionForNewPivot() and by
        // anything that needs to map a direction/offset rather than a point.
        QTransform linearPart() const;
 
        // The pivot-centered matrix to pass to QGraphicsItem::setTransform().
        QTransform toMatrix() const;
 
        bool operator==(const ShapeTransform &other) const;
        bool operator!=(const ShapeTransform &other) const { return !(*this == other); }
};
 
// Canonical decomposition of an arbitrary 2x2 linear map into the five
// scalars above, always returning skewY == 0 (all shear folded into
// skewX -- matching how most authoring tools represent shear on export).
// Rebuilding via ShapeTransform::linearPart() from the result reproduces
// the input matrix exactly; the individual scalar values are not
// guaranteed to match whatever scalars (if any) originally produced that
// matrix, only the matrix itself is guaranteed to match.
ShapeTransform decomposeLinear(const QTransform &linear);
 
// Position adjustment needed when the pivot moves, so the shape does not
// visibly jump on screen: call once, at the end of a pivot-handle drag,
// alongside setting the new pivot.
QPointF compensatedPositionForNewPivot(
                const QPointF &position,
                const QPointF &oldPivot,
                const QPointF &newPivot,
                const QTransform &linearPart);
 
#endif // SHAPETRANSFORM_H