Introduction to Qt Programming

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Introduction to Qt Programming

• Nitish Jaisoor

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Agenda

• The need for GUI programming
• Why Qt?
• Introduction to the Qt GUI toolkit
• What's involved in GUI design
• Part 1 Widgets the visible stuff
• Part 2 Signals the hidden stuff
• Part 3 Code snippets
• References
• QA

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The need for GUI programming

• The need to present all the options available to
  the user in an easy, pleasing style
• Front ends to console based applications can make
  them easier to use
• Linux newbies find GUIs very user friendly
• Pictorial presentation of data is possible

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Why Qt?

• Some common toolkits GTK, Qt, Tk, Visual Studio
  IDE.
• Licensing issues
• Cross platform portability
• Object oriented design
• Development language C or C?
• Ease of learning
• Well structured documentation

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Introduction to the Qt GUI toolkit

• Developed by Trolltech AS
• Based on OO C
• Available for Linux, Win32, Mac OsX, Embedded
• Basic C knowledge required
• Qt Object model
• Applications developed using Qt
• Reference documentation
• Useful tools QtDesigner, qmake

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What's involved in GUI design

• Obtain the requirements
• List out the functionality required
• Map the functionality to a GUI element
• Group similar functional elements
• Plan a user friendly layout
• User friendliness Error messages, Help dialogs
• Connect the functions and GUI elements

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Part-1 Widgets the visible stuff

• A user interface object that can process user
  input and draw graphics
• Properties of a widget
• Types of widgets
• Parent and child widgets

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Part-1 (cont.) Widget types
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Part 1 (cont.) Parents and children
Main Widget (QWidget)
Button 1 (QPushButton)
Label (QLabel)
Button 2 (QPushButton)
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Part 2 Signals the hidden stuff

• Signals and Slots provide an effective means of
  communication between objects
• They provide the functionality to the widget
  element while hiding the actual processing

Object 1
Signal 1 Signal 2
Object 2
Signal 1
Slot 1
Slot 1 Slot 2
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Part 2 (cont.) Signals and Slots
Slot displayMessage()
MessageLabel-gt setText(Welcome!)
Signal clicked()
Slot qApp-gtquit()
Signal clicked()
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Part 2 (cont.) Events and stuff

• Events are delivered to objects when a certain
  event takes place
• Strong support for events like mouse events,
  timer events, etc.
• Timers enable the scheduling of events in an
  object

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Part 3 Code snippets

• A simple widget
• A widget with a label and 2 buttons
• The above with signals and slots
• A small timer application

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References

• The Qt documentation with the distribution or
  at http//www.trolltech.com
• Programming with Qt Matthias Kalle Dalheimer
  (O'Reilly)
• OSS code get them at sites like
  http//apps.kde.com

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QA

• Contact information nitish_jaisoor_at_infosys.com