Validation callback only called once if no value returned by it

[BloodyRain2k]

So I was working on another PR for the designer's UI and I needed to get a callback for some of the code template properties.

Being completely new to Tk and barely having started half a year ago with Python, I just went with the "validate" callbacks.

But since I don't know the inner workings of either Tk nor PyGubu, I found out that if a "validate" callback doesn't return any value, it is never called a 2nd time.

Is that on purpose?

[alejandroautalan]

Hello @BloodyRain2k,

But since I don't know the inner workings of either Tk nor PyGubu, I found out that if a "validate" callback doesn't return any value, it is never called a 2nd time.
Is that on purpose?

Yes, that is the default behavior. If you don't return a boolean value the validation is disabled. According to tk documentation:

The Tk themed entry widget only disables validation if one of the validation scripts raises an error, or if -validatecommand does not return a valid boolean value. (Thus, it is not necessary to re-enable validation after modifying the entry value in a validation script).

You have some validation examples here:

pygubu-designer/examples/user_input/userinputapp.py

Lines 82 to 89 in 7153c7e

	def validate_entry_cb(self, d_action, p_entry_value):
	is_valid = True
	if d_action == "1": # Insert
	if not p_entry_value.islower():
	is_valid = False
	if len(p_entry_value) > 10:
	is_valid = False
	return is_valid

And here:

pygubu-designer/examples/7guis/02_temperature_converter/tempconvapp.py

Lines 39 to 51 in 7153c7e

	def temp_validate(self, d_action, p_entry_value, w_entry_name):
	is_valid = True
	if d_action == "1": # Insert
	try:
	temperature = float(p_entry_value)
	widget = self.mainwindow.nametowidget(w_entry_name)
	if widget is self.tempc:
	self.calculate_fahrenheit(temperature)
	else:
	self.calculate_celsius(temperature)
	except ValueError:
	is_valid = False
	return is_valid

Regards
Alejandro A.