How to make button exit pin_wait_change call

[tingeman]

I am looking for a workaround to make a button trigger the pin_wait_change() call to return.

The desired functionality can be obtained with a checkbox:

from pywebio.output import * 
from pywebio.pin import *

def button_callback(val):
    # trigger a change event here to exit the pin_wait_change call
    pass

put_markdown("# Test case")

put_row([
    put_column([
        put_select('select1', label='Choose:', options=['option1','option2']),
        None,
        put_input('input1', label='Write some text:'),
        ]),
    None,
    None,
    put_column([
        put_markdown('Show some **random** text *here*\nMore text...\nAnd some concluding remarks.'),
        ]),
    ])
put_row([
    put_checkbox('checkbox', options=['check to proceed']),
    #put_buttons(['proceed'], onclick=button_callback)
    ])
    
loop_flag = True
while loop_flag:
    result = pin_wait_change(['checkbox'])
    if result['name'] == 'checkbox':
        loop_flag = False

put_markdown('We have left the `while` loop')

Button clicks apparently do not trigger a change.
Is there a workaround to make this happen? e.g. by sending a message from the button onclick-callback? Or through run_js (called from callback)?

Thanks.

[wang0618]

If you just want to add a button to submit the form of pin widgets, you don't need the pin_wait_change() at all, just use pywebio.pin.pin object to access the value of pin widgets in the button's callback:

from pywebio.output import *
from pywebio.session import *
from pywebio.pin import *


def main():
    put_markdown("# Test case")

    put_row([
        put_column([
            put_select('select1', label='Choose:', options=['option1', 'option2']),
            None,
            put_input('input1', label='Write some text:'),
        ]),
        None,
        None,
        put_column([
            put_markdown('Show some **random** text *here*\nMore text...\nAnd some concluding remarks.'),
        ]),
    ])

    def submit():
        put_markdown('`select1` =  `%s`' % pin.select1)
        put_markdown('`input1` =  `%s`' % pin.input1)

    put_buttons(['check to proceed'], onclick=[submit])

    hold()


pywebio.start_server(main, port=8080)

[wang0618]

If you need a way to exit the pin_wait_change call, it will be a bit complicated:

from pywebio.output import *
from pywebio.session import *
from pywebio.pin import *
import threading
from queue import Queue

import pywebio


class PinChangeQueue:
    def __init__(self, names, maxsize=10):
        self.names = names
        self.mq = Queue(maxsize=maxsize)
        self.stopped = False

    def start(self):
        def mq_append():
            while not self.stopped:
                change = pin_wait_change(self.names)
                self.mq.put(change)

        t = threading.Thread(target=mq_append)
        register_thread(t)
        t.start()

    def get(self):
        if self.stopped:
            raise RuntimeError("The queue is closed")
        return self.mq.get()

    def stop(self):
        self.mq.put(None)
        self.stopped = True


def main():
    put_markdown("# Test case")

    put_row([
        put_column([
            put_select('select1', label='Choose:', options=['option1', 'option2']),
            None,
            put_input('input1', label='Write some text:'),
        ]),
        None,
        None,
        put_column([
            put_markdown('Show some **random** text *here*\nMore text...\nAnd some concluding remarks.'),
        ]),
    ])

    mq = PinChangeQueue(['select1', 'input1'])

    put_buttons(['Stop watching'], onclick=[mq.stop])

    mq.start()
    while not mq.stopped:
        changed_info = mq.get()
        put_code(str(changed_info))

    put_text('Stop watching Pin widgets')

pywebio.start_server(main, port=8080)

[wang0618]

Update: in the latest version (v1.4) of pywebio, you can use pin.put_actions() to exit the pin_wait_change call

[tingeman]

Excellent, thank you very much!
And thanks for the previous replies as well, I managed to get something working, but this will be much simpler!