Hi there,

I have two pieces of Ruby code, which do essentially the same. I
created the first one during experimenting with the GTK dialog display
functions, and the second was aimed on creating a Rubyish MessageBox
object from it. The first works correctly and displays the message box
- the second fails with a quite strange error message:
--------------------------------------------------------------
/opt/rubies/ruby-1.9.1-p378/lib/ruby/gems/1.9.1/gems/ffi-0.6.3/lib/ffi/
types.rb:46:in `find_type': Unable to resolve type
'string' (TypeError)
	from /opt/rubies/ruby-1.9.1-p378/lib/ruby/gems/1.9.1/gems/ffi-0.6.3/
lib/ffi/variadic.rb:47:in `call'
	from (eval):3:in `g_object_set'
	from gtkbox.rb:66:in `show'
	from gtkbox.rb:76:in `<main>'
-------------------------------------------------------------

What's the matter? As far as I know, :string as a regular type in
FFI.

Here's the (working) first attempt:
-------------------------------------------------------------
#!/usr/bin/env ruby
#Encoding: UTF-8
require "ffi"

module GTK

  extend FFI::Library

  ffi_lib("gtk-x11-2.0.so")

  attach_function(:gtk_init, [:pointer, :pointer], :void)
  attach_function(:gtk_set_locale, [], :void)
  attach_function(:gtk_message_dialog_new,
[:pointer, :int, :int, :int, :string], :pointer)
  attach_function(:g_object_set, [:pointer, :varargs], :void)
  attach_function(:gtk_dialog_run, [:pointer], :int)
  attach_function(:gtk_widget_destroy, [:pointer], :void)
end

GTK.gtk_init(nil, nil)
GTK.gtk_set_locale()
dialog = GTK.gtk_message_dialog_new(nil, 0, 0, 2, "title")
GTK.g_object_set(dialog, :string, "secondary-text", :string,
"text", :pointer, nil)
GTK.gtk_dialog_run(dialog)
GTK.gtk_widget_destroy(dialog)
-------------------------------------------------------------

And here's the (non-working) second:
-------------------------------------------------------------
#!/usr/bin/env ruby
#Encoding: UTF-8
require "ffi"
module MessageBox

  class GTKBox

    module Functions
      extend FFI::Library

      @init = false

      def self.init
        return false if @init
        begin
          ffi_lib("gtk-x11-2.0.so")

          enum :type, [ :gtk_message_info,
                                :gtk_message_warning,
                                :gtk_message_question,
                                :gtk_message_error,
                                :gtk_message_other
                              ]

          enum :buttons, [:gtk_buttons_none,
                                    :gtk_button_ok,
                                    :gtk_buttons_close,
                                    :gtk_buttons_cancel,
                                    :gtk_buttons_yes_no,
                                    :gtk_buttons_ok_cancel
                                    ]

          attach_function(:gtk_init, [:pointer, :pointer], :void)
          attach_function(:gtk_set_locale, [], :void)
          attach_function(:gtk_message_dialog_new,
[:pointer, :int, :type, :buttons, :string], :pointer)
          attach_function(:g_object_set, [:pointer, :varargs], :void)
          attach_function(:gtk_dialog_run, [:pointer], :int)
          attach_function(:gtk_widget_destroy, [:pointer], :void)

          #Initialize GTK and set it to the current locale.
          gtk_init(nil, nil)
          gtk_set_locale()

          @init = true
        rescue LoadError
          raise(NotImplementedError, "GTK+ >= 2.10 is not installed on
your system.")
        end #begin
      end #init
    end #Functions

    attr_reader :title
    attr_reader :text
    attr_accessor :icon
    attr_accessor :buttons

    def initialize(title, text)
      GTKBox::Functions.init
      @title = title
      @text = text
      @icon = :gtk_message_info
      @buttons = :gtk_button_ok
    end

    def show
      dialog = Functions.gtk_message_dialog_new(nil, 0, @icon,
@buttons, @title)
      Functions.g_object_set(dialog, :string, "secondary-
text", :string, @text, :pointer, nil)
      Functions.gtk_dialog_run(dialog)
      Functions.gtk_widget_destroy(dialog)
    end

  end

end

msgbox = MessageBox::GTKBox.new("title", "text")
msgbox.show
-------------------------------------------------------------

In case if you wonder why I don't define the FFI methods in
MessageBox::GTKBox::Functions directly, the answer is that I want to
create a system-independant library of displaying message boxes. And
if someone uses that library on Windows, FFI tries to load the GTK
shared object file which results in a program crash since it isn't
there. Now this is just the case if someone tries to display a GTK box
on Windows (which would work if GTK is installed, I know, but that's
for later).

I also noticed that if I removed the call to the g_object_set()
function, everything works fine, so I suppose there's something wrong
when resolving :varargs.

I'm using ruby 1.9.1p378 (2010-01-10 revision 26273) [x86_64-linux] on
Ubuntu Karmic Koala. I think that code works for every Linux that has
GTK+ installed, but if not, please correct me since I'm planning to
make a Gem for those message dialog functions in GTK+, KDE, Windows...

Any ideas?

Marvin


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