Re: Key press events on Canvas

[John Coppens <john jcoppens com>]

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