1. Slide design: Dr. Mark L. Hornick
SE3910
5/22/2018
SE3910 Week 5, Class 3
Today Qt
Perhaps Physical Datarate Limits
In Lab: No Quiz
17q3:
1-2,4,6-7,10-15,17,22,26-36
Print slides 20,21 on half sheets
SE-2811
Slide design: Dr. Mark L. Hornick
Content: Dr. Hornick
Errors: Dr. Yoder
Dr. Josiah Yoder

2. GUI Toolkits Java C# C/C++ AWT Swing SWT Java FX WPF Windows Forms
CS2852
5/22/2018
GUI Toolkits
Java
AWT
Swing
SWT
Java FX C#
WPF
Windows Forms
Silverlight
GTK#
C/C++ Qt
FLTK
GTK
Motif
MFC
SE Dr. Josiah Yoder
Slide style: Dr. Hornick
Much Material: Dr. Schilling
Dr. Yoder

3. What makes a good toolkit?
CS2852
5/22/2018
What makes a good toolkit?
Make table, fill in a few elements
Do “Boardshot”
SE Dr. Josiah Yoder
Slide style: Dr. Hornick
Much Material: Dr. Schilling
Dr. Yoder

4. Qt Features Fully object-oriented Utility classes
5/22/2018
Qt Features
Fully object-oriented
Utility classes
Consistent interfaces
OpenGL support
Rich set of widgets (controls)
Network support
Database support
Have native look and feel
Plugin support
Unicode/Internationalization support
Drag and drop
Customizable appearance
GUI builder
SE Dr. Josiah Yoder
Slide style: Dr. Hornick
Much Material: Dr. Schilling
Dr. Josiah Yoder

5. Qt Widgets Java Swing Qt CS2852 5/22/2018 Print large for me!
SE Dr. Josiah Yoder
Slide style: Dr. Hornick
Much Material: Dr. Schilling
Dr. Yoder

6. CS2852
5/22/2018
Example QT Widgets
SE3910 Real Time Systems
Dr. Yoder

7. QT Built in Dialog Boxes
CS2852
5/22/2018
QT Built in Dialog Boxes
File dialog
Font dialog
Color dialog
Printer dialog
Similar to Java…
SE3910 Real Time Systems
Dr. Yoder

8. Layouts Java Qt FlowLayout GridLayout BorderLayout BoxLayout
SE3910
5/22/2018
Layouts
Java
FlowLayout
GridLayout
BorderLayout
BoxLayout Qt
FlowLayout (ex)
QGridLayout
BorderLayout (ex)
QHBoxLayout
QVBoxLayout
SE Dr. Josiah Yoder
Slide style: Dr. Hornick
Much Material: Dr. Schilling
Dr. Josiah Yoder

9. Layouts in Java and Qt Layouts in Java Layouts in Qt (in JFrame)
SE3910
5/22/2018
Layouts in Java and Qt
Layouts in Java
(in JFrame)
setLayout(layout)
add(button)
Layouts in Qt
(in QMainWindow)
layout->add(button)
widget->setLayout(layout)
setCentralWidget(widget)
SE Dr. Josiah Yoder
Slide style: Dr. Hornick
Much Material: Dr. Schilling
Dr. Josiah Yoder

10. Events/Signals Java Qt What Design Pattern is this? Event
CS2852
5/22/2018
Events/Signals
Java
Event
E.g. ActionEvent
Event Listener
E.g. ActionListener
How does Java initiate an event? Qt
Signal
E.g. clicked()
Slot
E.g. on_pushButton_clicked
emit
What Design Pattern is this?
SE Dr. Josiah Yoder
Slide style: Dr. Hornick
Much Material: Dr. Schilling
Dr. Yoder

11. CS2852
5/22/2018
Custom Events in Java
How do you register an event with an event source in Java?
How do you create your own event in Java?
How do you fire an event in java?
Define MOC and qmake on board
SE Dr. Josiah Yoder
Slide style: Dr. Hornick
Much Material: Dr. Schilling
Dr. Yoder

12. Custom Events in QT emit progressNotification(1000 * seconds);
CS2852
5/22/2018
Custom Events in QT
How do you register an event with an event source in QT?
connect(button, SIGNAL(clicked()), qApp, SLOT(quit()));
How do you create your own event in QT?
signals:
void clicked();
How do you fire an event in QT?
emit progressNotification(1000 * seconds);
Define MOC and qmake on board
SE Dr. Josiah Yoder
Slide style: Dr. Hornick
Much Material: Dr. Schilling
Dr. Yoder

13. Threading – qthreads (with corrections)
SE3910
5/22/2018
Threading – qthreads (with corrections)
Java
qthreads
java.lang.Thread
#include <QThread>
No external jar needed
(moc and friends take care of this)
Thread t = new Thread(r)
t.start();
QThread *t = new QThread;
moveToThread(t); // note here
interface Runnable {
void run(); }
QObject (e.g. QWidget (e.g. QMainWindow))
t.join();
connect the QThread::finish() signal to a slot that checks if all threads are done.
Object o;
QMutex
synchronized(o) { …
} … /* Garbage coll. */
Avoid sharing memory entirely…
… see code example…
????
Dr. Josiah Yoder

14. Useful if you are into Qt slots/signals == events
5/22/2018
Useful if you are into Qt slots/signals == events
“A QThread should be used much like a regular thread instance: prepare an object (QObject) class with all your desired functionality in it. Then create a new QThread instance, push the QObject onto it using moveToThread(QThread*) of the QObject instance and call start() on the QThread instance. That’s all.”
I have successfully used this approach.
SE-2811
Dr.Yoder
Dr. Josiah Yoder

15. Qt’s connect method http://doc.qt.io/qt-5/qobject.html#connect
SE-2811
Dr.Yoder

16. Qt Connection types 1 2 3 0x80 Constant Value Description
Constant
Value
Description
Qt::AutoConnection
(Default) If the receiver lives inthe thread that emits the signal, Qt::DirectConnection is used. Otherwise, Qt::QueuedConnection is used. The connection type is determined when the signal is emitted.
Qt::Direct Connection 1
The slot is invoked immediately when the signal is emitted. The slot is executed in the signalling thread.
Qt::Queued Connection 2
The slot is invoked when control returns to the event loop of the receiver's thread. The slot is executed inhe t receiver's thread.
Qt::Blocking QueuedConnection 3
Same as Qt::QueuedConnection, except that the signalling thread blocks until the slot returns. This connection must not be used if the receiver lives in the signalling thread, or else the application will deadlock.
Qt::Unique Connection
0x80
This is a flag that can be combined with any one of the above connection types, using a bitwise OR. When Qt::UniqueConnection is set,QObject::connect() will fail if the connection already exists (i.e. if the same signal is already connected to the same slot for the same pair of objects). This flag was introduced in Qt 4.6.
SE-2811
Dr.Yoder

17. Coding example. Exercise:
Both the Java and Qt solutions will behave poorly if I start multiple threads.
Predict how each solution will behave if I:
Click start
// what happens? (For Java? For Qt?)
Click stop
SE-2811
Dr.Yoder

18. Week 10 Class 1 Communicating with Qt from a Non-Qt thread SE-2811
Dr.Yoder

19. Need invokeMethod
Code example:
QMetaObject::invokeMethod(&objWithSlot, “slotMethodName”, Qt::QueuedConnection, Q_ARG(QString, QString(“Hello!”)))
(But avoid smart quotes)
Like SwingUtilities.invokeLater()
SE-2811
Dr.Yoder

20. Sharing Memory
If you pass a pointer through a slot, both sender and receiver will have a pointer to the same memory.
Some memory management care is needed to avoid issues here.
SE-2811
Dr.Yoder

21. Slide design: Dr. Mark L. Hornick
References
EB: Derek Malloy, Exploring Beaglebone, Wiley, 2015 Laplante and Ovaska, Real-Time Systems Design and Analysis, Fourth Edition, Wiley, 2012
SE-2811
Slide design: Dr. Mark L. Hornick
Content: Dr. Hornick
Errors: Dr. Yoder