From: Stefano Crocco <stefano.crocco@...>
Date: 2009-05-12T15:17:11+09:00
Subject: Re: (mandriva,eclipse,Qt) elementary problem : signals and slots

On Monday 11 May 2009, lolveley wrote:
> |hi,
> |
> |I would like to make a little program using Qt : it's a displayer /
> |converter between farenheit and celsius degrees.
> |I also want to use QtDesigner.
> |
> |I made a little widget with QtDesigner, and this widget contains two
> |dials(dial and dial_2) and two spinboxes(kind of textboxes) (spinbox and
> |spinbox_2).
> |There are some connections : see below for the ruby file I obtained with
> |the tool rbuic4 (which converts the ".ui" file into ".rb").
> |my problem is this : I want that some changes made in dial_2 modify dial
> |(and then spinbox), eg :
> |    0 celsius degrees => 32 farenheit degrees.
> |
> |here is the file made by rbuic4 and after this my try to modify the slot
> |setValue (but it doesn't run: the value of dial is always the same as
> |the one of dial_2.

I don't know why it doesn't work, as I never used the designer to make 
signal/slot connections. I'd say it should work, but there might be some 
limitations which I'm not aware of. My suggestion is to use a custom widget 
class instead of a generic Qt::Widget and to implement the slot which converts 
the values there. Here's how the tmp_dsc_form.rb could look like:

require 'Qt4'
require 'temp.rb'

class MyWidget < Qt::Widget
  
  slots 'change_values(int)'
  
  def initialize
    super
    @ui = Ui_Form.new
    @ui.setupUi self
    connect @ui.dial_2, SIGNAL('valueChanged(int)'), self, 
SLOT('change_values(int)')
  end
  
  def change_values val
    new_value = (1.8*val+32).to_i
    @ui.spinBox.value = new_value
    @ui.dial.value = new_value
  end
  
end

une_appli=Qt::Application.new(ARGV)
un_wdg = MyWidget.new
un_wdg.show
une_appli.exec

Of course, if you use this you can remove the connections made from the 
designer.

I hope this helps

Stefano