The QNX Photon MicroGUI was a technological feat in its time. It gained popularity in the mid-1990's when QNX released a 1.44Mb bootable floppy with the QNX Operating System, the Photon GUI, networking, web browser, file browser, and several demo applications. QNX continued to develop and support Photon through 2014, but as GUI development systems matured — and users' expectations for GUIs increased — Blackberry's QNX is now focusing on the basics of drawing to the screen (e.g. QNX Screen) and left other aspects of Graphical User Interfaces to those who do it best (e.g. Qt) This presentation would be of particular interest to people looking to upgrade their software from an existing Photon system to Qt. It discusses the differences and similarities between the Photon and Qt application development platforms and how one may migrate from one to the other.

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Migrating from
QNX Photon to Qt
Bobby Chawla <bchawla@ics.com>
Integrated Computer Solutions, Inc.

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Introduction
● Working with ICS for about four years now
● Taste for real-time software development
● Used to work with Process Control Systems for industry:
○ Pulp & Paper machines
○ Lots of QNX development
● Offered to work on QNX itself
● About five years developing various parts of Photon

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Agenda
● Introduction
● What is (was) Photon?
● What is Qt?
● Anatomy of an application
● Architecture differences
● Qt Signals and slots
● Widget comparisons
● When to port
● Porting from QNX
● Conclusion

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What is (was) Photon?
● Photon : A name with multiple meanings:
○ Light particle
○ QNX/Photon MicroGUI
■ typically used with Neutrino
○ Photon UI project (Javascript framework to create UIs)
○ Photon OS distribution
… Probably More … .

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What is (was) Photon?
● Photon : A name with multiple meanings:
○ Light particle
○ QNX/Photon MicroGUI
■ typically used with Neutrino
○ Photon UI project (Javascript framework to create UIs)
○ Photon OS distribution
We are talking about the QNX/Photon MicroGUI .

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What is (was) Photon… cont. ● Started in the Mid-90s
● Had a Windows 95 look and feel:
○ “modern” at the time
● Evolved with more GUI options

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What is(was) Photon… cont.
● Deprecated Could say Depreciated - Appropriate verb
● QNX v6.32 - Full implementation
● QNX v6.4 - Reduced widget set:
○ Removed browser & email applications
○ Removed PtTerminal
■ though PtTty was still there
● QNX v6.5 - Essentially the windowing system was still there:
○ But not designed to be a desktop OS
● QNX v6.6 - Unsupported:
○ But die-hards could import the 6.5 executables
● QNX v7 - Unavailable - Now it’s deprecated

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What is Qt?
● Cross-platform application framework
● Supports all major desktop, mobile, embedded platforms
○ Windows, Mac OS, Linux, iOS, Android, QNX, etc.
● Written in C++
● Not just for GUI, but includes portable abstraction for most OS features
○ File i/o, strings, containers, networking, etc.
● Around since 1991
● Used by approximately 1 million developers in over 70 industries
● Owned by The Qt Company
● Available under GPL/LGPL and commercial licenses

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What is Qt? - Qt Widgets
● Traditional building blocks for
GUI applications in Qt:
○ e.g. QButton, QLabel,
QTextEdit
● Can use Qt Designer - a GUI
builder for designing dialogs and
screens
● Have native look on each
platform
● Originally designed for desktop
applications, but also usable on
mobile and embedded.

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What is Qt? - QML (aka Qt Quick)
● Simple JSON-like declarative language
● Provides basic elements to build up user interfaces
● Elements support properties, signals, methods
● Makes it easy to define animated, fluid, touchscreen interfaces
● Qt Quick Controls provide widget-like UI elements
● Backed by full JavaScript engine
● Qt Creator IDE has a QML Designer
○ developers typically write code by hand (QML Designer getting better)
● Mostly targeted at mobile and embedded
○ but also supported on desktop platforms

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What is Qt? - Qt on QNX
● Qt has been available as an option for QNX development since 2010
● Qt widgets provide similar classes and mechanisms to Photon’s
● Typically find source code to Qt, configure for QNX, and compile
● Given the current customer base of QNX-7 - QNX is encouraging QML:
○ Partially configured for QML already in Momentics
○ Since this presentation is about porting from Photon,
■ we will focus on Qt widgets

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Anatomy of an Application
● At a high level, both Photon & Qt GUI applications are:
○ Event driven
○ Similar parent/child relationships
■ parent window
■ every widget has a parent which helps keep things organized
● e.g. when the parent gets deleted, the child cleans up as well
■ dialogs - children of parent’s windows
○ Interactions
■ Photon uses callbacks vs. Qt using “signals and slots”
○ Qt separates widgets from layout managers

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Architecture Differences
● Photon (conceptually) is an entire graphical system:
○ Though not as well documented, just as easy to create an app that captures
Photon events, thus being able to create your own:
■ graphics driver
■ mouse controller
■ screen capture app
■ virtual keyboard
■ other IO device

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Architecture Differences… cont.
● Those of you familiar with Photon will know about:
○ Pg….() functions - Raw graphics functions
○ Ph….() functions - Open Photon channels, create regions, collect/emit
events
○ Pt….() functions - Create, Manipulate & Destroy widgets
● Qt:
○ Qt widget classes map mostly to Pt….() functions
○ Mature ecosystem of other classes for portability & convenience
■ e.g. stacks, accessing filesystem, strings

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Architecture Differences… cont.
● Typically Qt is run in a third-party’s windowing environment:
○ Qt has backends for different graphics rendering environments
■ X11/xcb, OpenGL/ES, Linux frame buffer, etc.
■ look & feel designed to look native on the device
● same application looks/behaves slightly differently on a Mac than on
Linux or Windows
○ If working with a specialized board
■ need to speak with the hardware (BSP) vendor to interface with new
devices

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Architecture Differences… cont.
Application development: PhAB , Qt Designer (GUI builder) & Qt Creator (IDE).

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Architecture Differences… cont.
● Photon uses “PhAB”,
● Can compile/link in PhAB
● PhAB - not your average
application builder:
○ No source code created for
PhAB windows/dialog
○ GUI component info
written as binary data as
part of the executable

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Architecture Differences… cont.
● Qt Creator (and Designer) is
not your average application
builder either:
○ Full development suite
○ Architecture-safe classes
○ PhAB/Photon users will
appreciate how easily tasks
get done (e.g. menus)

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Architecture Differences… menus

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Qt Signals & Slots
● Another term that can have different meanings: “Signals”:
○ QNX developers associate “Signals” as an operating system message
■ Signal can be passed from one process to another
■ Interrupts the receiving process, and process the signal
■ The call does not block the calling process
● Qt “Signals” are not the same as Linux/POSIX signals above:
○ Qt Signals & Slots are a one-to-many messaging system that lets Qt
“Objects” communicate within a process
○ Could be blocking function call, or could be queued
○ No “return” values from a signal
● Which differ from Boost Signals/Slots - allow return values from the “slots”

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Qt Signals & Slots… cont.
● Qt signals are an expanded form of callbacks that allow separation of UI
elements from business logic
● Signals are emitted by Qt objects when event occurs (e.g. button pressed)
● Slots are methods that can be called in response to a signal
● Typically connect signals and slots at run-time
● Qt uses “moc” tool to generate meta object information about signals/slots
● Type safe alternative to callbacks, checked at compile time or run time

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Widget Comparison - Menus and Options
Functionality Photon Qt Major Differences
Horizontal Menubar PtMenuBar QMenuBar QMenuBar has several insert Item
methods.
Pulldown Popup Menu PtMenu QMenu Qt provides a cleaner abstraction
using QMenu.
The common object for pulldowns
popups, and menubars
Menu button PtMenuButton QMenu
Combo Box PtComboBox QComboBox
Toggle or Multiple-selection
options
PtToggleButton
(Pt_TOGGLE_RADIO)
QRadioButton or
QCheckBox

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Widget Comparison - Dialogs
Functionality Photon Qt
Error PtAlert() QErrorMessage
Information PtNotice() QMessageBox
Question PtAlert() QMessageBox
Warning PtAlert() QMessageBox
Progress PtProgress widget QProgressDialog
Simple Input PtPrompt() QInputDialog
File Chooser PtFileSelection() QFileDialog
HTML/Web display PtWebClient widget QWebView
Generic/Custom PtWindow container QDialog
● Italicized Photon
items (such as
PtAlert()) are
convenience
functions which
use widgets to
build a dialog

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Widget Comparison… cont.
● Examples of widgets that are not 1 to 1 relationships:
○ PtTimer
○ RtTrend
● Qt has a large user base with many contributors:
○ Many sophisticated Qt widgets that don't exist in Photon are available from
3rd
party vendors

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Widget Comparison - Containers vs. Layouts
● PtContainer (or it’s subclasses) allow the automatic placement of widgets in a:
○ FILL_LAYOUT (Horizontal / Vertical)
○ ROW_LAYOUT (Horizontal/Vertical with options for Justify, Wrap and Pack)
○ GRID_LAYOUT
○ ANCHOR_LAYOUT
● In Qt, layouts are more sophisticated:
○ Layouts are separated from any widget subclassed off of QWidget
○ Container widgets can manage their children using QWidget::setLayout()

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When to Port / When to Consider Rewrite
● Photon is deprecated / newer hardware not supported
○ Eventually will run out of hardware options
○ Or user expectations for a device increase
● What code can you typically keep and what do you need to rewrite?
● Design aspects that makes it easier to port, e. g.
○ Good separation of UI and business logic.
○ Much of your application can be dissected into Model-View-Controller
(MVC) portions

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Object Oriented Design 101
● Qt is based off C++:
○ Photon apps are usually ‘C’ based
○ Need to port some or all of your code to C++.
○ Your team may need to learn object-oriented design.
○ May require re-architecting (e.g. to separate GUI from business logic).
● C++ applications typically better at compartmentalizing,
○ Scale better for larger projects

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Object
Oriented
Design
“101”

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Object Oriented Design 101… cont.
● Created the same application in Photon & Qt
● In Photon had a functional relation PtText → callback → PtSetArg( PtLabel )
● Can do a similar connection with Qt:
○ QLineEdit → signal to QObject::AddHello → signal to QLabel
● However, a cleaner implementation is to create a ‘Hello’ widget:
○ Create a QHelloLabel as a subclass of QLabel,
○ QHelloLabel displays the string with ‘Hello’ prepended
○ QLineEdit → signal to QHelloLabel
Less code, less portions that can break, easier to test, ….

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Porting from QNX
Note for native QNX-ers
● QNX has been, and continues to be a “Message passing” architecture:
○ Lightweight transition from one process to another
○ Designed for many thousands (millions) of messages
○ Many aspects of QNX based on message passing
○ Photon is no exception
● If porting to other operating systems:
○ Can’t rely as heavily on OS-level message passing
○ Buffered streams more common
○ QNX is a POSIX OS, therefore a port to Linux should be easier

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Conclusion
● Most applications would have one to one mapping to Qt widgets
● Need help getting started? ICS developers:
○ Have many years of experience with Qt and QNX/Photon
○ Can assist you with the port (while your developers continue advancing
with current development)
○ Can help you get started by analyzing your application and coming up with
a plan of action

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Questions?