Transcript Ruby GUI Toolkits

Ruby GUI Toolkits
29-Mar-16
Available GUI toolkits
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The Tk GUI toolkit is a part of the Ruby distribution
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Other toolkits are FXRuby, GTK+, FLTK, Gt, probably others
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Tk is badly documented, does not support native widgets, and is generally
regarded as ugly
However, Tk is perfectly functional and easily available
All have some significant disadvantages
My less-than-extensive research (about an hour's worth) leads me
to think that wxRuby2 is the best choice
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Advantages: Fairly stable, mature, cross-platform, native look-and-feel,
good selection of widgets
Disadvantage: C++ oriented
The home page is at http://wxruby.rubyforge.org/wiki/wiki.pl
Download from RubyForge at http://rubyforge.org/frs/?group_id=35
Modern event-driven programs
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Multiple sources of
input
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mouse clicks
keyboard
timers
external events
In all modern
languages, this is
handled with an event
loop
Wait for event
Dispatch event
Quit
Java hides the event loop
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The event loop is built into Java GUIs
Interacting with a GUI component (such as a button)
causes an event to occur
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An Event is an object
You create Listeners for interesting events
The Listener gets the Event as a parameter
In Ruby, the event loop is not built in
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However, Ruby GUI systems provide one—you just have
to use it
“Hello world” in Tk
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require 'tk'
root = TkRoot.new { title 'Our first Tk App' }
label = TkLabel.new(root) do
text 'Hello, world!'
pack("padx" => 90)
end
Tk.mainloop
All subsequent widgets will be contained by root
The block uses instance_eval; the title method belongs to the
newly created instance
pack is a geometry manager; it takes a hash as an argument
The mainloop is the event handler
Geometry managers
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Geometry managers are like Java’s layout managers
Ruby has three geometry managers: grid, place, and
pack
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pack is like Java’s FlowLayout; things are put into it in the
order they are defined
grid is like Java’s GridbagLayout, and is complex
place specifies pixel coordinates, and is tedious
pack is the best compromise for ordinary use
Allocation rectangle
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Every Ruby widget has an allocation rectangle, and is put
somewhere inside that rectangle
Here are the options for the hash argument to pack:
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The 'side' option tells where the allocation rectangle goes in the
container--'top' (default), 'bottom', 'left', or 'right'
The 'expand' option tells whether the allocation rectangle should be
expanded to fill the remaining space--the value is either '0' (default,
meaning don’t expand) or '1'
The 'anchor' option tells where the widget goes in the allocation
rectangle--'n', 'ne', 'e', 'se', 's', 'sw', 'w', 'nw', or 'center'
The 'fill' option tells how to stretch the widget to fill the container-'none' (default), 'x', 'y', or 'both'
The 'padx' and 'pady' options specify margins
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The default is pixels
You can suffix a number with a letter: i for inches, p for points, m for
millimeters, or c for centimeters
Packing example I
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require 'tk'
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root = TkRoot.new() { title "Packing Example" }
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button = TkButton.new(root) { text "First, rightmost" }
button.pack("side"=>"right", "fill"=>"y")
entry = TkEntry.new(root).pack("side"=>"top", "fill"=>"x")
entry.insert(0, "Entry on the top")
label = TkLabel.new() { text "to the right" }
label.pack("side"=>"right")
Packing example II
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image = TkPhotoImage.new('file'=>"background.gif", 'height'=>50)
img_label = TkLabel.new(root) { image image }.pack("anchor"=>"e")
text = TkText.new(root) { width 20; height 5 }.pack("side"=>"left")
text.insert('end', "Left in canvas")
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TkMessage.new(root) { text "Message in the Bottom" }.pack("side"=>"bottom")
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Tk.mainloop()
Event handling example
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require 'tk'
root = TkRoot.new() { title "Click the Button" }
button = TkButton.new(root) {
text "Hello..."
command proc {
puts "...world!"
}
}
button.pack()
Tk.mainloop()
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This brings up a window with a button labeled “Hello...”
When the button is clicked, “...world!” is printed to the console
RubyGems
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RubyGems is a standardized way of installing, upgrading, and
removing Ruby packages
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It uses a centralized repository, so you don’t even have to know where to
download packages from
If you installed InstantRails, you already have RubyGems
Example:
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C:\ruby\InstantRails\rails_apps>gem install wxruby2-preview
Select which gem to install for your platform (i386-mswin32)
1. wxruby2-preview 0.0.40 (i686-darwin8.8.2)
2. wxruby2-preview 0.0.40 (i386-mswin32)
3. wxruby2-preview 0.0.40 (powerpc-darwin7.9.0)
4. wxruby2-preview 0.0.40 (i686-linux)
5. Skip this gem
6. Cancel installation
>1
Successfully installed wxruby2-preview-0.0.40-i686-darwin8.8.2
“HelloWorld” in wxRuby2
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require 'rubygems'
require 'wx'
include Wx
# Extend the Wx::App class
class HelloWorld < App
# Define what the application is going to do when it starts
def on_init
# Make a frame with the title "Hello World"
helloframe = Frame.new(nil, -1, "Hello World")
# Put the text "Hello World" in that frame
StaticText.new(helloframe,-1,"Hello World")
# Make the window appear
helloframe.show()
end
end
# Make the program actually do it!
HelloWorld.new.main_loop
Using wxRuby2
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A tutorial for wxRuby2 is at
http://wxruby.rubyforge.org/wiki/wiki.pl?WxRuby_Tutorial
Some of the examples don’t work as printed
The following code, at the beginning of the file, seems to solve
the problem:
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begin
require 'wx'
rescue LoadError => no_wx_err
begin
require 'rubygems'
require 'wx'
rescue LoadError
raise no_wx_err
end
end
include Wx
Using a BoxSizer
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# Code from previous slide goes here
class MyApp < Wx::App
def on_init()
frame = Wx::Frame.new(nil, -1, 'Sizer happiness')
frame.set_client_size(Wx::Size.new(200,200))
sizer = Wx::BoxSizer.new(Wx::VERTICAL)
text = Wx::TextCtrl.new(frame, -1, 'Type in here',
Wx::DEFAULT_POSITION, Wx::DEFAULT_SIZE,
Wx::TE_MULTILINE)
sizer.add(text, 1, Wx::GROW|Wx::ALL, 2)
button = Wx::Button.new(frame, -1, 'Click on this')
sizer.add(button, 0, Wx::ALIGN_RIGHT, 2)
frame.set_sizer(sizer)
frame.show()
end
end
MyApp.new.main_loop()
Comments
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Ruby has no real “Ruby-like” GUI system
Tk is the default if you are OK with just basic
functionality and don’t care much about appearance
You have several choices if you want something better
than Tk
This situation may change as Ruby becomes
increasingly popular
The End