Question

I’m trying to write a custom clock widget in Ruby Qt gem install qtbindings The clock should update every second with the current time. It doesn’t, the code seems perfect, why doesn’t this work?

require "Qt4"

class ClockLabel < Qt::Label
    attr_accessor :timer
    def initialize(date_format = '%Y-%d-%mT%H:%M:%S')
        super()
        @date_format = date_format
        self.set_text(Time.now.strftime date_format)
    end

    def paint_event(event)
        super(event)
        painter = Qt::Painter.new(self)
        painter.draw_text(event.rect.x, event.rect.y, Time.now.strftime(@date_format))
    end

    def start
        @timer = Qt::Timer.new(self)
        self.connect(@timer, SIGNAL('timeout()'), self, SLOT('update()'))
        @timer.start(1000)
    end
end

if __FILE__ == $PROGRAM_NAME
    app = Qt::Application.new([])
    clock = ClockLabel.new()
    clock.start
    clock.show
    app.exec()
end

Answer 1

It works if I replace the connect call with

  @timer.connect(SIGNAL :timeout) {
    set_text(Time.now.strftime @date_format)
    update
  }

paint_event never gets called and can be omitted. That gives the hint that the widget did not change, so we change it when the timer triggers.