在之前的一篇文章中，实现了QT场景视图的打印功能，主要通过render函数来实现，非常简单和方便。
在实际的项目需求中，除了打印整个场景外，还需要对单个图形进行打印操作，基于item的图形可以在paint函数中打在QPrinter作为绘图设备实现打印，基于Widget的图形则提供了更方便的render函数，都可以很好地实现。但是，如果图形存在父子嵌套关系，则需要在打印该图形时，连同其子图形以及孙子图形也要一起打印出来，为此，本文对此进行了研究，方便参考。
目的：实现QT场景视图中父子关系打印
具体要求： 打印某图形时，打印其为根的一颗图形树; 打印左上角不留空白区域
主要代码，仅供参考：
MyItem.h
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#ifndef MYITEM_H
#define MYITEM_H #include <QGraphicsItem> class QPainter; class MyItem : public QGraphicsItem { public: explicit MyItem(QGraphicsItem *parent = nullptr); MyItem(const QString &name, QGraphicsItem *parent = nullptr); // custom item type enum {Type = UserType + 1}; // overriding bounding rect QRectF boundingRect() const override; // overriding type() int type() const override; // overrriding paint() void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = nullptr) override; // recursive print items void printAll(QPainter *painter, // painter int xOffset = 0, // x偏移 int yOffset = 0, // y偏移 bool root = true); // 是否是最顶层item protected: // overriding mouse events virtual void mouseDoubleClickEvent(QGraphicsSceneMouseEvent *event); private: // actual drawing void draw(QPainter *painter, // painter int xOffset = 0, // x偏移 int yOffset = 0 // y偏移 ); // find item from full parent/child tree void findInherit(MyItem *itemFind, bool &find); private: QString m_name; QColor m_color; QPointF m_scenePos; }; #endif // MYITEM_H |
MyItem.cpp
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#include "MyItem.h"
#include <QPainter> #include <QGraphicsScene> #include <QRandomGenerator> #include <QPrinter> #include <QPrintDialog> MyItem::MyItem(QGraphicsItem *parent) : QGraphicsItem (parent) , m_name("") { // radom color m_color.setRed(QRandomGenerator::global()->bounded(255)); m_color.setGreen(QRandomGenerator::global()->bounded(255)); m_color.setBlue(QRandomGenerator::global()->bounded(255)); // item options setFlag(ItemIsMovable); setFlag(ItemIsSelectable); } MyItem::MyItem(const QString &name, QGraphicsItem *parent) : QGraphicsItem (parent) , m_name(name) { // radom color m_color.setRed(QRandomGenerator::global()->bounded(255)); m_color.setGreen(QRandomGenerator::global()->bounded(255)); m_color.setBlue(QRandomGenerator::global()->bounded(255)); // item options setFlag(ItemIsMovable); setFlag(ItemIsSelectable); } QRectF MyItem::boundingRect() const { // outer most edges return QRectF(0, 0, 100, 100); } int MyItem::type() const { // Enable the use of qgraphicsitem_cast with this item. return Type; } void MyItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) { Q_UNUSED(option); Q_UNUSED(widget); draw(painter); } void MyItem::printAll(QPainter *painter, int xOffset, int yOffset, bool root) { if (root) { bool bFindH = false; bool bFindV = false; unsigned int xPos = scenePos().x(); unsigned int yPos = scenePos().y(); // 如果其child item不在其坐标的左上区域，则移除打印的左上角空白区域 QRectF rectBlankH = QRectF(0.0, 0.0, scene()->width(), scenePos().y()); QRectF rectBlankV = QRectF(0.0, 0.0, scenePos().x(), scene()->height()); // 水平区域 QList<QGraphicsItem *> itemListH = scene()->items(rectBlankH); foreach (QGraphicsItem *item, itemListH) { if (item->type() == MyItem::Type) { MyItem *itemTmp = qgraphicsitem_cast<MyItem *>(item); if (itemTmp != nullptr) { bool find = false; findInherit(itemTmp, find); if (find) { bFindH = true; if (itemTmp->m_scenePos.y() < yPos) { yPos = itemTmp->m_scenePos.y() < 0 ? 0 : itemTmp->m_scenePos.y(); } } } } } if (bFindH) { painter->translate(-QPointF(0.0, yPos)); } else { painter->translate(-QPointF(0.0, scenePos().y())); } // 垂直区域 QList<QGraphicsItem *> itemListV = scene()->items(rectBlankV); foreach (QGraphicsItem *item, itemListV) { if (item->type() == MyItem::Type) { MyItem *itemTmp = qgraphicsitem_cast<MyItem *>(item); if (itemTmp != nullptr) { bool find = false; findInherit(itemTmp, find); if (find) { bFindV = true; if (itemTmp->m_scenePos.x() < xPos) { xPos = itemTmp->m_scenePos.x() < 0 ? 0 : itemTmp->m_scenePos.x(); } } } } } if (bFindV) { painter->translate(-QPointF(xPos, 0.0)); } else { painter->translate(-QPointF(scenePos().x(), 0.0)); } } draw(painter, m_scenePos.x(), m_scenePos.y()); QList<QGraphicsItem *> childList = childItems(); foreach (QGraphicsItem *item, childList) { if (item->type() == MyItem::Type) { MyItem *myChilditem = qgraphicsitem_cast<MyItem *>(item); if (myChilditem != nullptr) { myChilditem->printAll(painter, m_scenePos.x(), m_scenePos.y(), false); } } } } void MyItem::mouseDoubleClickEvent(QGraphicsSceneMouseEvent *event) { QPrinter printer; QPrintDialog printDlg(&printer); if (printDlg.exec()) { QPainter painter(&printer); QRectF rect = scene()->sceneRect(); painter.translate(-rect.x(), -rect.y()); printAll(&painter); } } void MyItem::draw(QPainter *painter, int xOffset, int yOffset) { QRectF rect = boundingRect(); qreal width = rect.width(); qreal height = rect.height(); rect.setX(xOffset); rect.setY(yOffset); rect.setWidth(width); rect.setHeight(height); painter->drawText(rect.x() + rect.width() / 2, rect.y() + rect.height() / 2, m_name); QPen pen(m_color, 2); painter->setPen(pen); painter->drawRect(rect); m_scenePos = scenePos(); } void MyItem::findInherit(MyItem *itemFind, bool &find) { QList<QGraphicsItem *> childList = childItems(); if (childList.size() > 0) { foreach (QGraphicsItem *item, childList) { if (item->type() == MyItem::type()) { MyItem *itemChild = qgraphicsitem_cast<MyItem *>(item); if (itemChild != nullptr) { if (itemChild == itemFind) { find = true; } itemChild->findInherit(itemFind, find); } } } } } |
测试代码：
C++ Code
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m_view = new QGraphicsView(this);
m_scene = new QGraphicsScene(); m_scene->setSceneRect(0.0, 0.0, 800.0, 800.0); m_view->setScene(m_scene); // 绘制场景坐标系 QPen pen(Qt::black, 1, Qt::DashLine); m_scene->addLine(QLineF(-400.0, 0.0, 400, 0.0), pen); m_scene->addLine(QLineF(0.0, -400, 0.0, 400.0), pen); // item-based MyItem *item = new MyItem("parent"); m_scene->addItem(item); MyItem *child1 = new MyItem("child1"); child1->setParentItem(item); child1->setPos(-100, -100); m_scene->addItem(child1); MyItem *child2 = new MyItem("child2"); child2->setParentItem(item); child2->setPos(100, 100); m_scene->addItem(child2); MyItem *child21 = new MyItem("child21"); child21->setParentItem(child2); child21->setPos(50, 50); m_scene->addItem(child21); |