Recipe 21.14. Creating a GUI Application with wxRuby
Problem
You want to write a portable GUI application that looks better than a Tk application.
Solution
Use the
wxRuby library, available as a third-party download. It uses native GUI widgets on Windows, Unix, and Mac OS X. It's got many more features than the Tk library, and even greater complexity.
Here's a very simple wxRuby application (Figure 21-3):
#!/usr/bin/ruby -w
# wxtrout.rb
require 'wxruby'
class TroutApp < Wx::App
def on_init
frame = Wx::Frame.new(nil, -1, 'Tiny wxRuby Application')
panel = Wx::StaticText.new(frame, -1, 'You are a trout!',
Wx::Point.new(-1,1), Wx::DEFAULT_SIZE,
Wx::ALIGN_CENTER)
frame.show
end
end
TroutApp.new.main_loop
Discussion
The simple wxRuby application has the same basic structure as its Tk cousin (see Recipe 21.12). A top-level widget is created (here called a Frame) and a label (StaticText) widget is added to it. The application then goes into an event loop, listening for and retrieving events like mouse clicks.
A
wxRuby version of the Tk stopwatch program is also similar, although much longer.
wxRuby code tends to be more verbose and less idiomatic than Ruby Tk code.
The core methods are nearly unchanged, because they have little to do with the GUI:
#!/usr/bin/ruby -w
# wx_stopwatch.rb
require 'wxruby'
class StopwatchApp < Wx::App
def start
@start = Time.now
@button.set_label('Stop')
@button.refresh
@frame.evt_button(@button.get_id) { stop }
@timer.start(100) # The timer should tick every 100 milliseconds.
end
def stop
@button.set_label('Start')
@button.refresh
@frame.evt_button(@button.get_id) { start }
@timer.stop
@accumulated += @elapsed
end
def reset
stop
@accumulated, @elapsed = 0, 0
@label.set_label('00:00:00.0')
@frame.layout
end
def tick
@elapsed = Time.now - @start
time = @accumulated + @elapsed
h = sprintf('%02i', (time.to_i / 3600))
m = sprintf('%02i', ((time.to_i % 3600) / 60))
s = sprintf('%02i', (time.to_i % 60))
mt = sprintf('%1i', ((time - time.to_i)*10).to_i)
newtime = "#{h}:#{m}:#{s}:#{mt}"
@label.set_label(newtime)
@frame.layout
end
The menu bar takes a lot more code in wxRuby than in Tk. Every widget in a wxRuby program has a unique ID, which must be passed in when you register an event handler. I've defined a hardcoded ID for each menu item, so that after I create the "menu item" widget, I can pass its unique ID into the event-handler registration method, evt_menu. You can really sense the underlying C code here:
# Constants for the IDs of the menu items.
START_MENU = 10
STOP_MENU = 11
EXIT_MENU = 12
RESET_MENU = 13
# Constant for the ID of the timer widget, used below.
TIMER_ID = 14
def on_init
@accumulated, @elapsed = 0, 0
@frame = Wx::Frame.new(nil, -1, '
wxRuby Stopwatch')
menu_bar = Wx::MenuBar.new
program_menu = Wx::Menu.new
menu_bar.append(program_menu, '&Program')
program_menu.append(START_MENU, '&Start', 'Start the stopwatch')
@frame.evt_menu(START_MENU) { start }
program_menu.append(STOP_MENU, 'S&top', 'Stop the stopwatch')
@frame.evt_menu(STOP_MENU) { stop }
menu_exit = program_menu.append(EXIT_MENU, "E&xit\tAlt-X",
'Exit the program')
@frame.evt_menu(EXIT_MENU) { exit }
reset_menu = Wx::Menu.new
menu_bar.append(reset_menu, '&Reset')
reset_menu.append(RESET_MENU, '&Reset', 'Reset the stopwatch')
@frame.evt_menu(RESET_MENU) { reset }
@frame.set_menu_bar(menu_bar)
wxRuby uses Sizer objects to pack widgets into their display areas. The BoxSizer object used below arranges widgets within the frame vertically, so that the label will be above the stopwatch button.
sizer = Wx::BoxSizer.new(Wx::VERTICAL)
@label = Wx::StaticText.new(@frame, -1, '00:00:00.0')
font = Wx::FontData.new.get_chosen_font
font.set_point_size(16)
font.set_weight(Wx::FONTWEIGHT_BOLD)
@label.set_font(font)
sizer.add(@label, 1, Wx::ALIGN_CENTER)
The button and the timer work more or less like their Tk equivalents. The call to @frame.set_sizer tells the root widget to use our vertical BoxSizer when deciding how to arrange widgets on the screen (Figure 21-4).
@button = Wx::Button.new(@frame, -1, 'Start')
@frame.evt_button(@button.get_id) { start }
sizer.add(@button, 0, Wx::ALIGN_CENTER, 2)
@frame.set_sizer(sizer)
@frame.show
@timer = Wx::Timer.new(@frame, TIMER_ID)
@frame.evt_timer(TIMER_ID) { tick }
end
end
StopwatchApp.new.main_loop
See Also
You need to download (and, on Unix systems, compile)
wxRuby as a Ruby extension; you can get it from http://wxruby.rubyforge.org/; the wxRuby developers provide a good installation guide at http://wxruby.rubyforge.org/wiki/wiki.pl?Installation The wxRuby wiki has a lot of useful information, including a simple tutorial at http://wxruby.rubyforge.org/wiki/wiki.pl?Getting_Started; the wxRuby distribution also comes with many good sample applications in its samples/ directory The web site for wxWidgets (the underlying library to which wxRuby is a binding) also has lots of good reference material: http://www.wxwidgets.org/; you just have to be able to translate the C++-style class and method names into Ruby style (for instance, WxLabel::SetLabel becomes Wx::Label#set_label)
|
No comments:
Post a Comment