Text in graphicsView in Qt

Question

I am creating an application in Qt in which I can add different entities in graphics view on click of a button. I want that user can add text in graphics view when he clicks the push button for same. How can I make use of QGraphicsTextItem to do so? I have different buttons in my application like for drawing line, circle in which user specifies the points for doing so. Similarly I have a button to add text. I have seen we can have the implementation of adding text in graphics view as :

addText("hello")

This text is already defined. I want that text should be entered at run time, it should not be statically or predefined.

Answer 1

The information you give is quite sparse. From what it sounds like, you should be able to get the QTextDocument associated with the QGraphicsTextItem by calling QGraphicsTextItem::document () . If you don't want to do anything fancy, you should be able to set/replace the text of the item by calling QTextDocument::setPlainText ( const QString & text ) . If you want to prompt the user to enter text, you can use the static QInputDialog::getText method to get a single QString from the user.

Does this help? If this doesn't match your use case you might need to provide a bit more context.

Edit: posting a minimal example on how you can place text in a QGraphicsView/Scene. You click the mouse button in a particular location, it will ask you to enter text and then put the text where the mouse click happened. Does this help?

Edit 2: adding a more complete yet still dummy example below the first one showing creation of a mainwindow with a custom widget and a dummy button to toggle on/off text insertion. Note that this is certainly not production ready code, it should show the working principle and was not optimized or beautified in any way.

#include <QApplication>
#include <QGraphicsScene>
#include <QGraphicsView>
#include <QMouseEvent>
#include <QInputDialog>

class MyGraphicsView: public QGraphicsView
{
public:
  MyGraphicsView( QGraphicsScene *scene, QWidget *parent = 0) : QGraphicsView(scene,parent) {}

public slots:
  void mousePressEvent( QMouseEvent * event );



};

void MyGraphicsView::mousePressEvent( QMouseEvent * event )
{
  const QPoint &pos = event->pos();

  bool ok;
  QString text = QInputDialog::getText(this, tr("QInputDialog::getText()"),
                                   tr("Please enter your text"), QLineEdit::Normal,
                                   "Replace with your text", &ok);

  if (!ok || text.isEmpty()) return;

  QGraphicsTextItem *textItem = this->scene()->addText(text);
  textItem->setPos(mapToScene(pos));

}


int main( int argc, char **argv )
{
    QApplication app(argc, argv);
    QGraphicsScene scene;
    scene.setSceneRect( -100.0, -100.0, 200.0, 200.0 );

    MyGraphicsView view( &scene );
    view.show();

    return app.exec();
}

'Complete' Example

mainwindow.ui (created with qt designer)

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>640</width>
    <height>480</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <layout class="QGridLayout" name="gridLayout">
    <item row="0" column="0">
     <widget class="MyGraphicsView" name="graphicsView"/>
    </item>
    <item row="1" column="0">
     <widget class="QToolButton" name="toolButton">
      <property name="text">
       <string>Add Text</string>
      </property>
     </widget>
    </item>
   </layout>
  </widget>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>640</width>
     <height>27</height>
    </rect>
   </property>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
 </widget>
 <customwidgets>
  <customwidget>
   <class>MyGraphicsView</class>
   <extends>QGraphicsView</extends>
   <header location="global">mygraphicsview.h</header>
  </customwidget>
 </customwidgets>
 <resources/>
 <connections/>
</ui>

mainwindow.h

#ifndef MYMAINWINDOW_H
#define MYMAINWINDOW_H

#include "mygraphicsview.h"
#include <QGraphicsScene>
#include "ui_mainwindow.h"
#include <QtCore>

class MyMainWindow: public QMainWindow, private Ui::MainWindow
{
  Q_OBJECT
 public:
  MyMainWindow( QWidget *parent = 0 );

  public slots:
  void on_toolButton_clicked( bool checked ) { graphicsView->setAddText(checked); }


};

#endif // MYMAINWINDOW_H                   

mainwindow.cpp

#include "mainwindow.h"

MyMainWindow::MyMainWindow( QWidget * ) {
  setupUi(this);
  QGraphicsScene *scene = new QGraphicsScene;
  scene->setSceneRect( -100.0, -100.0, 200.0, 200.0 );
  toolButton->setCheckable(true);
  graphicsView->setScene(scene);

}

mygraphicsview.h

#ifndef MYGRAPHICSVIEW_H
#define MYGRAPHICSVIEW_H

#include <QGraphicsView>
#include <QGraphicsScene>

class MyGraphicsView: public QGraphicsView
{
  Q_OBJECT
public:
  MyGraphicsView( QWidget *parent = 0) : QGraphicsView(parent), addText(false) {}
  void setAddText(bool state) {addText = state;}
  public slots:
  void mousePressEvent( QMouseEvent * event );

 private:
  bool addText;

};

#endif // MYGRAPHICSVIEW_H         

mygraphicsview.cpp

#include "mygraphicsview.h"
#include <QApplication>
#include <QGraphicsScene>
#include <QGraphicsView>
#include <QMouseEvent>
#include <QInputDialog>
#include <QGraphicsTextItem>




void MyGraphicsView::mousePressEvent( QMouseEvent * event )
{
  if( ! addText) return;

  const QPoint &pos = event->pos();
  bool ok;
  QString text = QInputDialog::getText(this, tr("QInputDialog::getText()"),
                                   tr("Please enter your text"), QLineEdit::Normal,
                                   "Replace with your text", &ok);

  if ( !ok || text.isEmpty()) return;

  QGraphicsTextItem *textItem = this->scene()->addText(text);
  textItem->setPos(mapToScene(pos));

}

main.cpp

#include "mainwindow.h"
#include "mygraphicsview.h"
#include <QApplication>


int main( int argc, char **argv )
{
    QApplication app(argc, argv);
    MyMainWindow m;
    m.show();
    return app.exec();
}