QGraphicsItem 交互式调整大小

Question

我已经分叉了项目https://github.com/cesarbs/sizegripitem，这是一个使用 8 个处理程序调整大小的交互式 QGraphicsItem，问题是如果我将我的主 QGraphicsItem 设置为可选，当我拖动处理程序时，主 QGraphicsItem 移动而不是调整大小, 下面是 SizeGripItem.cpp 的来源

/*
 * 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);
    }
}

Answer 1

在 SizeGripItem::HandleItem::itemChange 中设置父位置在这里看起来很奇怪。我认为 itemChange 函数可能不应该设置父项的位置。它应该只调整坐标并返回一个值。

在过去，我的做法有所不同。首先，删除 HandleItem 中的 ItemSendsGeometryChanges 标志。

然后为HandleItem实现mousePressEvent、mouseMoveEvent和mouseReleaseEvent。在 mouseMoveEvent 中，随着句柄的移动更新父级的边界矩形。

这允许将主 GraphicsItem 及其句柄设置为可选择和可移动。