WxWindows

1 Intro

• WxWindows is a cross-platform graphical toolkit library

  

• It’s a library for creating programs that have graphical user interfaces and can be run on different platforms
• Free (LGPL but can distribute derived binaries however you want)

2 On Windows

• WxWindows programs run on Windows (95, NT, XP, …)

3 On Unix

• WxWindows programs run on Linux, using GTK+

• Other Unix platforms also supported

4 On Macs

• WxWindows programs run on MacOS 9 and OS X

5 Sticking Out

• The leading-brand multi-platform toolkits impose their own look on programs using them
  • Tk, Java Swing, XUL, GTK+
• A program looks the same on all platforms
• But it doesn’t fit in on any platform
  • On Windows it doesn’t look like a Windows app ...
• Obvious aesthetic disruption
• Usability issues
  • Ctrl+A is ‘select all’ or ‘start of line’?
• Most baffling for users who run the app on a single OS

6 Blending in

• WxWindows is different
• Doesn’t have any widgets of its own
• Uses the actual native widgets of platform it’s running on
  • Not just its own widgets painted to disguise themselves as native
  • WxWindows provides a consistent programming interface to the different native platform toolkits
• A WxWindows program will look different on each platform
  • But it will always look like other native apps
  • Not obviously identifiable as a WxWindows program

7 Programing Languages

• WxWindows is a C++ library
  • The website claims that it isn’t a problem for C developers to switch to C++
• WxPython provides Python bindings
  • Seems to be a popular toolkit in the Python community
  • Python issues integretated in the WxWindows documentation
• WxPerl is the equivalent for … um, Perl
  • Not so well established
  • Docs are a little flaky

8 Using a Scripting Language

• Scripting languages such as Perl and Python lend themselves well to developing GUI programs
• Not having compilation greatly aids making small tweaks
  • And GUIs always need many small tweaks
• Generally speed isn’t an issue
  • The slowest part of a GUI program is usually the user
• Using WxPerl or WxPython means that your program can be deployed unchanged on multiple platforms
  • No need to compile separate editions for each OS
  • Even runs on platforms you don’t have

9 Sane Windows Development

• Developers allergic to Windows can share WxPerl or WxPython program directories on the network
• Run on Windows directly from those directories
  • Minimal interaction with a Windows computer

• For WxPerl using the .plw extension and associating it with wperl.exe quells Dos-prompt pop-up irritation

10 Bargepole Avoidance

• Using VNC can prevent even having to touch a Windows computer

11 Comparison

• Can run the same file locally to compare appearances

12 Multiple Platforms

• Presumably this would also work the other way round
  • Develop on Windows but also deploy on Linux
• Possible migration strategy
  • If planning to switch desktops from Windows to Linux, helps for application software to be familiar
  • Custom tools can be implemented with WxWindows and deployed on Windows now, knowing that they will work on Linux after switching
• Insurance policy
  • Even if only using Windows at the moment, can avoid being tied to it

13 Capabilities

• WxWindows includes the form controls you’d expect
  • Textboxes, labels, checkboxes, radio buttons…
• Not lowest-common denominator of supported platforms
  • Controls such as checklistboxes faked if necessary

  

• Also some non-graphical cross-platform classes
  • Printing, forking, config files, clipboard

14 Programming

• The WxWindows docs are comprehensive, and available in many formats
• But it isn’t something that can be picked up in an afternoon
• Complex library with lots of specific bits to get the hang of
  • Some idiosyncrasies
  • Learning process likely to involve frustration
• Putting controls on windows is a skill requiring practice
  • And squared paper
  • Widgets are different sizes on different platforms
  • Designs specified with relative sizes and positions

15 Positioning with Sizers

• The concept of sizers will be familiar to anybody with experience of nesting HTML tables
• The practice of sizers will be familiar to anybody who’s tried to find out train times on the National Rail website

  

• Seem manageable once you’ve got used to them

16 Object Objections

• The WxWindows API is quite verbose
• Object-oriented
  • Lots of method calls needed to do anything
  • Separate object trees for controls and sizers
• Quite common tasks often result in more code repetition than is strictly healthy
  • Possible to roll your own sub-classes and helper functions to hide the mess under the carpet
  • Specifying related controls in nested data structures can work well
• Other GUI toolkits appear to suffer from this too

17 XML Window Specifications

• Somebody had the idea that adding in an XML format for specifying window layouts might help with designs
• Well, I suppose it was worth a try
• WRC files are parsed by programs at run-time
• Enforced separation can be awkward
  • Using loops or sub-classes to set up similar controls
  • Initializing controls based on external data
  • Specifying event handlers to spring into action when controls are changed
• Might be useful for apps with fixed interfaces which gather all data before processing any of it

18 WxDesigner: a GUI GUI

19 WxDesigner

• Reasonable interface, once used to the icons
• Still need to think in terms of nested grids
  • Can’t just drop things anywhere on a window
  • Can’t wrap a further level of grid outside controls
  • Still need the squared paper
• Tedious repetition for editing similar controls
• Generates C++, Python, Perl, and XML
  • Dubious quality
• Commercial, with free trial version
• Other WxWindows form designers exist

20 Using WxDesigner

• WxDesigner is good for quickly realizing paper designs
  • Try out variations in layout
• Use it to discover the various WxWindows options
  • Teach yourself WxWindows from WxDesigner output
  • Generate the code for ‘difficult’ controls
• Generate first drafts in WxDesigner then hack by hand
  • Helper functions and loops for the repetitive bits
• Now I’ve learnt WxWindows it seems more efficient to code with it in a text editor
  • GUIs are vastly overrated

21 Cross-Platform Issues

• WxWindows programs look ‘right’ on different platforms
• Some aspects of usability dealt with
  • Mozilla development has highlighted many platform differences, such as dragging scroll-bar sliders
• But also ‘cultural’ differences between platforms:
  • ‘Exit’ or ‘Quit’ on the ‘File’ menu?
  • Expectation of built-in or external text editor
  • User home directories
  • Common file formats
• Can test for the OS adjust behaviour accordingly
  • But then need different docs for each edition

22 Community

• WxWindows and the WxPython and WxPerl bindings are all actively being developed
• Links and stuff on http://www.wxwindows.org/
• WxWindows has been around for 10 years
  • Created at Edinburgh Uni AI dept
• Sundry mailing lists exist

23 Installation

• WxWindows installation is mostly unsurprising
• Linux:
  • Source and RPMs are available on the website
  • No Debian package currently
  • WxPerl on CPAN, as the Wx module
• Windows:
  • Installer that works
  • PPMs for ActiveState Perl

24 Summary

• I quite like WxWindows
  • Well, the bits I don’t like have been encapsulated and are kept in quarantine
• Used with a scripting language it seems like a reasonably neat way of producing decent-looking GUI programs
  • And they fit in well with their surroundings
• The cross-platform capability is nice to have
  • Write programs that will run on other platforms even if there doesn’t seem to be an immediate need
  • One less thing tying you to a particular OS