Re: Key press events on Canvas

[Damon Chaplin <damonachaplin gmail com>]

On Sat, 2015-10-31 at 12:20 -0300, John Coppens wrote:
> On Fri, 30 Oct 2015 23:22:35 +0000
> Damon Chaplin <damonachaplin gmail com> wrote:
>
> > On Fri, 2015-10-30 at 14:24 -0300, John Coppens wrote:
> > > Hi all,
> > >
> > > I tried to react on keypress events over a Canvas widget. Though the
> > > code seems right (no compiler complaints), no events are generated.
> > > Button press/release events and Enter/Leave events work fine.
> > >
> > > I thought the button press events might be masked out, but even
> > > after    canvas.set_events(Gdk.EventMask.KEY_PRESS_EVENT), no events
> > > appeared.
> > >
> > > I'm using GooCanvas 2.0.2 (using introspection), and Python 3.4.3.
> > >
> > > Is there any way to detect keypresses?
> >
> > It should work. There is a page in the demo app to demonstrate it.
> >
> > Have you set the CAN_FOCUS widget flag, to let GTK+ know the canvas can
> > take the keyboard focus?
> >
> >   gtk_widget_set_can_focus (canvas, TRUE);
> >
> > Damon
>
> Hi Damon:
>
> Thanks for replying. Here's (some of) the code (I added can_focus for testing):
>
>       self.canvas = GooCanvas.Canvas()
> ...
>         self.canvas.set_events(Gdk.EventMask.KEY_PRESS_MASK)          # Makes no difference
>
>         self.canvas.connect("button-release-event", self.on_darea_button_released)
>         self.canvas.connect("key-press-event",      self.on_darea_key_pressed)
>         self.canvas.connect("key-release-event",    self.on_darea_key_released)
>         self.canvas.set_can_focus(True)                                       # Makes no difference
>
> ...
>
>     def on_darea_button_released(self, darea, event):                 # Gets called correctly
>         print("released")
>
>     def on_darea_key_pressed(self, darea, event):                     # Never gets called
>         print("key pressed")
>
>     def on_darea_key_released(self, darea, event):                    # Never gets called
>         print("key released")
>
> So, no luck with the can_focus setting. I'm using Python, so maybe a problem with the
> bindings? I believe I've seen a Python version of the demo - I'll try and search for
> it. I remember it did behave differently from the C version.
>
> John

You may need to make sure the canvas has the keyboard focus too, if
there are multiple widgets that can take the focus in the window.

Either manually by tabbing to it, or using gtk_widget_grab_focus().

(I doubt it is a bindings problem, as it is basic GTK+ stuff.)

Damon