path: root/qtruby/README

/***************************************************************************
 * 	(C) 2003 Richard Dale All rights reserved.                             *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as               *
 *   published by the Free Software Foundation; either version 2 of the    *
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Here is a Ruby SMOKE adaptor for Qt

Why ruby? From the rubytalk list

On 8/28/03 8:56 PM, "Scott Thompson" wrote:

>> : Can anyone give me a good reason why I would want to use Ruby over
>> Python?
>> 
>> Ruby smells better than Python. Also, it has cuter girls.
>> 
>> Python sometimes tastes better if you prepare it right.
> 
> I hadn't noticed the odor thing. It does have a faintly floral aroma
> doesn't it.
> 
> Of course it is no surprise that you can get more and cuter girls with
> Rubies than you can with Pythons.
> 
> Scott

So there you have it! :)

Here is 'Hello World' in QtRuby:

#!/usr/bin/ruby -w

require 'Qt'

a = Qt::Application.new(ARGV)
hello = Qt::PushButton.new("Hello World!", nil)
hello.resize(100, 30)
a.setMainWidget(hello)
hello.show()
a.exec()

Ruby 1.8 is unfortunately implicitly required as with 1.6.x it is not possible to:

   Make dynamic constants available (thus forcing syntax such as Qt.RichText rather than Qt::RichText)<br>
   Call super in the initialize method thus making subclassing of non trivial classes impossible

QtRuby features a very complete coverage of the Qt api:

	- You can call all Qt public and protected methods, and all friend methods
		such as bitBlt() etc
		
	- Virtual methods
		All virtual methods can be overriden, not just event handlers
		
	- Properties 
		'fooBar = 5' is a synonym for 'setFooBar(5)'
		
	- Predicates
		'if foo?' is a synonym for 'if isFoo()' or 'if hasFoo()'
		
	- Use underscore naming for method names instead of camel case if you 
		prefer. Any underscores in method names are removed, and the following
		character is capitalised. For example, you can use either of these two 
		forms to call the same method:
		
		create_standard_status_bar_action()
		
		createStandardStatusBarAction()
		
	- Operator overloading
		The full range of Qt operator methods is available, for example:
		
			p1 = Qt::Point.new(5,5)   => (5, 5)
			p2 = Qt::Point.new(20,20) => (20, 20)
			p1 + p2                   => (25, 25)
			
	- Declare signals and slots
	 	Signals and slots are declared as list of strings like this:
		
			slots 'setColor(QColor)', 'slotLoad(const QString&)'..
			signals 'clicked()'..
			
		Currently C++ type signatures must be used, a future version of QtRuby
			will allow ruby type signatures instead.
		
		Connect slots and signals like this:
					
			Qt::Object.connect( @_colormenu, SIGNAL( "activated( int )" ),
						 		self, SLOT( "slotColorMenu( int )" ) )
	
		And emit signals like this:
		
			emit colorChanged( black )

	- Constructors
		You can call constructors in the conventional style:
		
		    quit = Qt::PushButton.new("Quit", self, "quit")
			
		Or you can pass a block if you prefer:
		
			w = MyWidget.new { setCaption("foobar") }
			
		The block will be called in the context of the newly created instance.
		
		Ordinary arguments can be provided as well as a block at the end:
			
			w = MyWidget.new(nil) { setCaption("foobar") }
			
		They are run in the context of the new instance.
		
		And there's more! You can also pass an arg to the block, and it will
			be run in the context of the arg:
			
			w = MyWidget.new { |theWidget| theWidget.setCaption "foobar" }
			
	- Garbage Collection
		When a ruby instance is garbage collected, the underlying C++ instance will only be
		deleted if it isn't 'owned' by a parent object. Normally this will 'just work', but
		there are occasions when you need to delete the C++ ahead of garbage collection, and
		whether or not it has a parent. Use the dispose() and isDisposed() methods like this:
		
			item2.dispose
			if item2.isDisposed
				puts "item2 is disposed"
			end
			
	- C++ 'int*' and 'int&' argument types
		Ruby passes numeric values by value, and so they can't be changed when passed to a
		method. The Qt::Integer class provides a mutable numeric type which does get updated
		when passed as an argument. For example, this C++ method 'findByFileContent()':
		
			# static Ptr findByFileContent( const QString &fileName, int *accuracy=0 );

			acc = Qt::Integer.new(0)
        	fc = KDE::MimeType.findByFileContent("mimetype.rb", acc)
		
		It supports the arithmetic operators, and so expressions such as 'acc + 3' will work.
	
	- C++ 'bool*' and 'bool&' argument types
		There is a similar problem for bool arg types, and the mutable Qt::Boolean class can be
		used like this:
		
			# QFont getFont(bool * ok, const QFont&initial, QWidget* parent = 0, const char *name = 0);		
		
			ok = Qt::Boolean.new
			font = Qt::FontDialog.getFont(ok, Qt::Font.new("Helvetica [Cronyx]", 10), self)
			if !ok.nil? 
        		# font is set to the font the user selected
			else 
        		# the user canceled the dialog
			end
		
		Use 'nil?' to test the value returned in the Boolean

	- Debugging
		If a method call can't be matched in the Smoke library giving a 'method_missing' 
		error, you can turn on debugging to trace the matching process:
		
			a = Qt::Application.new(ARGV)
			Qt.debug_level = Qt::DebugLevel::High
			a.loadLibrary("foo")  # Non existent method

		Will give the following output:
		
			classname    == QApplication
			:: method == loadLibrary$
			-> methodIds == []
			candidate list:
			Possible prototypes:
        			static QWidget* QApplication::widgetAt(int, int, bool)
					...
		
		Here, the list of candidate methods 'methodIds' is empty
		
		Another debugging mechanism allows various trace 'channels' to be switched on.
		
		You can trace virtual method callbacks:
		    Qt::Internal::setDebug(Qt::QtDebugChannel::QTDB_VIRTUAL)
			
		Or trace QtRuby garbage collection:
		    Qt::Internal::setDebug(Qt::QtDebugChannel::QTDB_GC)
		
	- String i18n 
	
	   QtRuby supports $KCODE values of 'u', 'e' and 
	  's' or the corresponding '-K' options from the command line. Qt Designer
	  .ui files have UTF-8 strings so if you use any 8 bit UTF-8 characters, you
	  will need to set $KCODE='u' or use the -Ku command line option.
 	
	- Qt Designer
		A 'rbuic' tool is included in qtruby/rubylib/designer/rbuic to compile
		.ui files into ruby code. As described above, Qt Designer uses UTF-8.
		In addition to the options in the original uic C++ utility an '-x' flag
		has been added. This will generate a top level stub in the code:
		
		$ rbuic mainform.ui -x -o mainform.rb
		
		Will add this to the end of the generated code:

	        if $0 == __FILE__
                a = Qt::Application.new(ARGV)
                w = MainForm.new
                a.setMainWidget(w)
                w.show
                a.exec
            end
			
		Then you can test the example code straight away:
			
		$ ruby mainform.rb

	- Loading .ui files at runtime with QWidgetFactory
		You can load a Qt Designer .ui file at runtime with the qui extension,
		for example:
		
			require 'Qt'
			require 'qui'

			a = Qt::Application.new(ARGV)
			if ARGV.length == 0
				exit
			end

			if ARGV.length == 2
				QUI::WidgetFactory.loadImages( ARGV[ 0 ] )
    			w = QUI::WidgetFactory.create( ARGV[ 1 ] )
    			if w.nil?
					exit
				end
    			w.show()
    			a.connect( a, SIGNAL('lastWindowClosed()'), a, SLOT('quit()') )
    			a.exec()
			end
			
	- QtRuby shell
		You can use the QtRuby shell in bin/rbqtsh to create widgets 
		interactively from the command line.
			
	- API reference
		Use the bin/rbqtapi tool to discover which methods are available in
		the QtRuby api.
			
	- Example programs
		The best way to start programming QtRuby is to look at some existing
		code and start messing with it.. 
		The are various samples under qtruby/rubylib/examples.

	- Optional QScintilla text editing widget support
		Great for building your own ruby IDE..

Have Fun!

-- Richard