RawWidget does not recive updates

[Tillsten]

Here in the example below, the RawWidget does not register the changes to i.

from enaml.widgets.api import (MainWindow, Label, Container, Timer, RawWidget)
from enaml.core.api import Looper, Declarative, d_
from enaml.application import deferred_call

from atom.api import *
from enaml.qt import QtWidgets

class Model(Atom):
    i = Int()

    def update(self):
        self.i = self.i+1

class Test(RawWidget):
    __slots__ = ('___weakref___')

    i = d_(Int())

    def create_widget(self, parent):
        return QtWidgets.QWidget(parent=parent)

    @observe('i')
    def log(self, change):
        print(self.i)

enamldef Main(MainWindow):
    attr model = Model()    
    Test: raw:        
        i << model.i
    Label:
        text << str(model.i)
    func update():
        model.update()
    Timer: timer:
        interval = 200
        single_shot = False
        timeout :: deferred_call(update)
    activated ::
        timer.start()

[Tillsten]

Suprisingly I add an reference of i to widget itself it does work?

def create_widget(self, parent):
      wid = QtWidgets.QWidget(parent=parent)
      wid.i = self.i
      return wid

[frmdstryr]

enaml and atom are lazy (or should I say smart?). They don't do work that is unnecessary.

Since your Test widget is never using i the expression is never setup / observed. When you do self.i it then creates the observer.

Simply read i once and it works.

enamldef Main(MainWindow):
    attr model = Model()

    Test: raw:
        i << model.i
    Label:
        text << str(model.i)
    func update():
        model.update()
    Timer: timer:
        interval = 200
        single_shot = False
        timeout :: deferred_call(update)
    activated ::
        raw.i # Read i
        timer.start()

[Tillsten]

Thanks @frmdstryr, is there more documentation on this behavior? For a newbie like me it is absolutly not clear why it does not in the first place.

[MatthieuDartiailh]

I would have to check if it is documented but enaml does ignore creation events. However I need to ponder a bit more this specific example. I feel like after the first event it should work.

[sccolbert]

Change your Label to read the value from your Test widget instead of the model, and it will work. Frmdstryr is correct in that Enaml is as lazy as possible (it's a lazily evaluated dependency graph). If you never use the value, the expression won't be executed.

On Fri, Jan 29, 2021 at 9:49 AM Matthieu Dartiailh notifications@github.com wrote:

I would have to check if it is documented but enaml does ignore creation events. However I need to ponder a bit more this specific example. I feel like after the first event it should work.

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[Tillsten]

My real usecase is a little bit more complicated, i am not sure if this kind of redirection is always useful. At least now I know how to work around that issue.

[MatthieuDartiailh]

Closing feel free to reopen if needed.

[Tillsten]

I still think this should be at least advertised in the docs somewhere, since the behavior is not intuitive.