Observing return events in Field objects in enaml

person_view.enaml

#------------------------------------------------------------------------------
# Copyright (c) 2013, Nucleic Development Team.
#
# Distributed under the terms of the Modified BSD License.
#
# The full license is in the file COPYING.txt, distributed with this software.
#------------------------------------------------------------------------------
# 
# mods by Jason Sachs
#
from enaml.layout.api import hbox, vbox, align, spacer
from enaml.widgets.api import Window, Label, Field, Form, Container
from enaml.stdlib.fields import IntField

def field_signal_return_event(field, signal):
    field.proxy.widget.returnPressed.connect(lambda: signal.emit())

enamldef PersonForm(Form):
    attr person
    attr key_manager
    Label:
        text = 'First Name'
    Field: fname:
        text := person.first_name
    Label:
        text = 'Last Name'
    Field: lname:
        text := person.last_name
    Label:
        text = 'Age'
    IntField: age:
        minimum = 0
        value := person.age
    constraints = [
		field_signal_return_event(age, person.ageSignal),
        field_signal_return_event(fname, person.nameSignal),
        field_signal_return_event(lname, person.nameSignal)
	]

enamldef PersonView(Window):
    attr person
    PersonForm: form1:
        person := parent.person
        key_manager = keys

test1.py

#------------------------------------------------------------------------------
# Copyright (c) 2013, Nucleic Development Team.
#
# Distributed under the terms of the Modified BSD License.
#
# The full license is in the file COPYING.txt, distributed with this software.
#------------------------------------------------------------------------------
# 
# mods by Jason Sachs
#
from __future__ import print_function

from atom.api import Atom, Str, Range, Int, Bool, Signal, observe

import enaml
from enaml.qt.qt_application import QtApplication

class Person(Atom):
    """ A simple class representing a person object.

    """
    last_name = Str()

    first_name = Str()

    age = Range(low=0)
    
    nameSignal = Signal()
    ageSignal = Signal()
    
    debug = Bool(False)

    @observe('age')
    def debug_print(self, change):
        """ Prints out a debug message whenever the person's age changes.

        """
        if self.debug:
            templ = "{first} {last} is {age} years old."
            s = templ.format(
                first=self.first_name, last=self.last_name, age=self.age,
            )
            print(s)
            
    @observe('nameSignal')
    def namesig(self):
        print("NAME SIGNAL")

    @observe('ageSignal')
    def agesig(self):
        print("AGE SIGNAL")
            

if __name__ == '__main__':
    with enaml.imports():
        from person_view import PersonView

    john = Person(first_name='John', last_name='Doe', age=42)
    john.debug = True

    app = QtApplication()
    view = PersonView(person=john)
    view.show()

    app.start()

This modifies the Person tutorial to show how intercepting Return events in fields is pretty easy for the Qt backend. The relevant aspects of it are

def field_signal_return_event(field, signal):
    field.proxy.widget.returnPressed.connect(lambda: signal.emit())

and adding non-constraint function calls in the constraints section:

    constraints = [
		field_signal_return_event(age, person.ageSignal),
        field_signal_return_event(fname, person.nameSignal),
        field_signal_return_event(lname, person.nameSignal)
	]

where person.ageSignal and person.nameSignal are Signal objects defined in the model.

Then you can observe the signals and do whatever you want:

    @observe('nameSignal')
    def namesig(self):
        print("NAME SIGNAL")

    @observe('ageSignal')
    def agesig(self):
        print("AGE SIGNAL")

When you run test1.py and you press return in any of the fields, it will either print NAME SIGNAL for the first/last names, or AGE SIGNAL in the age field.