问题
i've forked the project https://github.com/cesarbs/sizegripitem that is a intercative QGraphicsItem resizing with 8 handlers, the problem is that if i set my main QGraphicsItem to be Selectable, when i drag the handlers, the main QGraphicsItem moves rather then being resized, bellow is the source for SizeGripItem.cpp
/*
* SizeGripItem - A size grip QGraphicsItem for interactive resizing.
*
* Copyright (c) 2011 Cesar L. B. Silveira
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#include <QBrush>
#include "SizeGripItem.h"
SizeGripItem::HandleItem::HandleItem(int positionFlags, SizeGripItem* parent)
: QGraphicsRectItem(-4, -4, 8, 8, parent),
positionFlags_(positionFlags),
parent_(parent)
{
setBrush(QBrush(Qt::lightGray));
setFlag(ItemIsMovable);
setFlag(ItemSendsGeometryChanges);
}
int SizeGripItem::HandleItem::positionFlags() const
{
return positionFlags_;
}
QVariant SizeGripItem::HandleItem::itemChange(GraphicsItemChange change,
const QVariant &value)
{
QVariant retVal = value;
if (change == ItemPositionChange)
{
retVal = restrictPosition(value.toPointF());
}
else if (change == ItemPositionHasChanged)
{
QPointF pos = value.toPointF();
switch (positionFlags_)
{
case TopLeft:
parent_->setTopLeft(pos);
break;
case Top:
parent_->setTop(pos.y());
break;
case TopRight:
parent_->setTopRight(pos);
break;
case Right:
parent_->setRight(pos.x());
break;
case BottomRight:
parent_->setBottomRight(pos);
break;
case Bottom:
parent_->setBottom(pos.y());
break;
case BottomLeft:
parent_->setBottomLeft(pos);
break;
case Left:
parent_->setLeft(pos.x());
break;
}
}
return retVal;
}
QPointF SizeGripItem::HandleItem::restrictPosition(const QPointF& newPos)
{
QPointF retVal = pos();
if (positionFlags_ & Top || positionFlags_ & Bottom)
retVal.setY(newPos.y());
if (positionFlags_ & Left || positionFlags_ & Right)
retVal.setX(newPos.x());
if (positionFlags_ & Top && retVal.y() > parent_->rect_.bottom())
retVal.setY(parent_->rect_.bottom());
else if (positionFlags_ & Bottom && retVal.y() < parent_->rect_.top())
retVal.setY(parent_->rect_.top());
if (positionFlags_ & Left && retVal.x() > parent_->rect_.right())
retVal.setX(parent_->rect_.right());
else if (positionFlags_ & Right && retVal.x() < parent_->rect_.left())
retVal.setX(parent_->rect_.left());
return retVal;
}
SizeGripItem::SizeGripItem(Resizer* resizer, QGraphicsItem* parent)
: QGraphicsItem(parent),
resizer_(resizer)
{
if (parentItem())
rect_ = parentItem()->boundingRect();
handleItems_.append(new HandleItem(TopLeft, this));
handleItems_.append(new HandleItem(Top, this));
handleItems_.append(new HandleItem(TopRight, this));
handleItems_.append(new HandleItem(Right, this));
handleItems_.append(new HandleItem(BottomRight, this));
handleItems_.append(new HandleItem(Bottom, this));
handleItems_.append(new HandleItem(BottomLeft, this));
handleItems_.append(new HandleItem(Left, this));
updateHandleItemPositions();
}
SizeGripItem::~SizeGripItem()
{
if (resizer_)
delete resizer_;
}
QRectF SizeGripItem::boundingRect() const
{
return rect_;
}
void SizeGripItem::paint(QPainter* painter,
const QStyleOptionGraphicsItem* option,
QWidget* widget)
{
}
#define IMPL_SET_FN(TYPE, POS) \
void SizeGripItem::set ## POS (TYPE v) \
{ \
rect_.set ## POS (v); \
doResize(); \
}
IMPL_SET_FN(qreal, Top)
IMPL_SET_FN(qreal, Right)
IMPL_SET_FN(qreal, Bottom)
IMPL_SET_FN(qreal, Left)
IMPL_SET_FN(const QPointF&, TopLeft)
IMPL_SET_FN(const QPointF&, TopRight)
IMPL_SET_FN(const QPointF&, BottomRight)
IMPL_SET_FN(const QPointF&, BottomLeft)
void SizeGripItem::doResize()
{
if (resizer_)
{
(*resizer_)(parentItem(), rect_);
updateHandleItemPositions();
}
}
void SizeGripItem::updateHandleItemPositions()
{
foreach (HandleItem* item, handleItems_)
{
item->setFlag(ItemSendsGeometryChanges, false);
switch (item->positionFlags())
{
case TopLeft:
item->setPos(rect_.topLeft());
break;
case Top:
item->setPos(rect_.left() + rect_.width() / 2 - 1,
rect_.top());
break;
case TopRight:
item->setPos(rect_.topRight());
break;
case Right:
item->setPos(rect_.right(),
rect_.top() + rect_.height() / 2 - 1);
break;
case BottomRight:
item->setPos(rect_.bottomRight());
break;
case Bottom:
item->setPos(rect_.left() + rect_.width() / 2 - 1,
rect_.bottom());
break;
case BottomLeft:
item->setPos(rect_.bottomLeft());
break;
case Left:
item->setPos(rect_.left(),
rect_.top() + rect_.height() / 2 - 1);
break;
}
item->setFlag(ItemSendsGeometryChanges, true);
}
}
回答1:
Setting the parent positions in SizeGripItem::HandleItem::itemChange looks odd here. I think that the itemChange function probably should not be setting the position of the parent item. It should only adjust coordinates and return a value.
In the past, I've done this a little differently. Firstly, remove the ItemSendsGeometryChanges flag in the HandleItem.
Then implement mousePressEvent, mouseMoveEvent and mouseReleaseEvent for HandleItem. In mouseMoveEvent, update the parent's bounding rect as the handle is moved.
This allows both the main GraphicsItem and its handles to be set as selectable and moveable.
来源：https://stackoverflow.com/questions/24159632/qgraphicsitem-interactive-resizing