(C++) QUndoCommand example 1

QUndoCommand example 1 is a QUndoCommand example.

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• Download the Qt Creator project 'CppQUndoCommandExample1' (zip)

Technical facts

Application type(s)

• Desktop application

Operating system(s) or programming environment(s)

• Lubuntu 12.10 (quantal)

IDE(s):

• Qt Creator 2.5.2

Project type:

• GUI application

C++ standard:

• C++98

Compiler(s):

• G++ 4.7.2

Libraries used:

• Qt: version 4.8.3 (32 bit)
• STL: GNU ISO C++ Library, version 4.7.2

 

 

 

 

 

Qt project file: CppQUndoCommandExample1.pro

 

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#------------------------------------------------- # # Project created by QtCreator 2013-04-21T19:59:08 # #------------------------------------------------- QT       += core gui greaterThan(QT_MAJOR_VERSION, 4): QT += widgets TARGET = CppQUndoCommandExample1 TEMPLATE = app SOURCES += main.cpp\         qtdialog.cpp \     qtbuttonincrementcommand.cpp HEADERS  += qtdialog.h \     qtbuttonincrementcommand.h FORMS    += qtdialog.ui

 

 

 

 

 

main.cpp

 

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#include <QApplication> #include "qtdialog.h" int main(int argc, char *argv[]) {   QApplication a(argc, argv);   QtDialog w;   w.show();      return a.exec(); }

 

 

 

 

 

qtbuttonincrementcommand.h

 

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#ifndef QTBUTTONINCREMENTCOMMAND_H #define QTBUTTONINCREMENTCOMMAND_H #include <QUndoCommand> struct QPushButton; struct QtButtonIncrementCommand : public QUndoCommand {   explicit QtButtonIncrementCommand(QPushButton * const button);   ///Virtual function supplied by QUndoCommand   void redo();   ///Virtual function supplied by QUndoCommand   void undo();   private:   QPushButton * const m_button; }; #endif // QTBUTTONINCREMENTCOMMAND_H

 

 

 

 

 

qtbuttonincrementcommand.cpp

 

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#include "qtbuttonincrementcommand.h" #include <cassert> #include <QPushButton> QtButtonIncrementCommand::QtButtonIncrementCommand(   QPushButton * const button)   : m_button(button) {   assert(m_button); } void QtButtonIncrementCommand::redo() {   const int current_number = m_button->text().toInt();   const int new_number = current_number + 1;   m_button->setText(QString::number(new_number) ); } void QtButtonIncrementCommand::undo() {   const int current_number = m_button->text().toInt();   const int new_number = current_number - 1;   m_button->setText(QString::number(new_number) ); }

 

 

 

 

 

qtdialog.h

 

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#ifndef QTDIALOG_H #define QTDIALOG_H #include <QDialog> namespace Ui {   class QtDialog; } struct QUndoStack; class QtDialog : public QDialog {   Q_OBJECT    public:   explicit QtDialog(QWidget *parent = 0);   ~QtDialog();    private slots:   void keyPressEvent(QKeyEvent *);   void on_button_clicked(); private:   Ui::QtDialog *ui;   QUndoStack * const m_stack; }; #endif // QTDIALOG_H

 

 

 

 

 

qtdialog.cpp

 

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#include "qtdialog.h" #include <QKeyEvent> #include <QUndoStack> #include "qtbuttonincrementcommand.h" #include "ui_qtdialog.h" QtDialog::QtDialog(QWidget *parent) :   QDialog(parent),   ui(new Ui::QtDialog),   m_stack(new QUndoStack(this)) {   ui->setupUi(this); } QtDialog::~QtDialog() {   delete ui; } void QtDialog::keyPressEvent(QKeyEvent * e) {   if ( (e->modifiers() & Qt::ControlModifier)     && !(e->modifiers() & Qt::ShiftModifier)     && e->key() == Qt::Key_Z)   {     m_stack->undo();   }   if ( (e->modifiers() & Qt::ControlModifier)     && (e->modifiers() & Qt::ShiftModifier)     && e->key() == Qt::Key_Z)   {     m_stack->redo();   } } void QtDialog::on_button_clicked() {   QtButtonIncrementCommand * const cmd     = new QtButtonIncrementCommand(ui->button);   //By pushing the command, redo is called   m_stack->push(cmd); }