Log viewer inside tabs issue

[marcin-koziol]

Description

I want to place the Log component in the tab, everything is OK, but to see the logs, you first need to switch to the Log viewer tab

from datetime import datetime
from nicegui import ui


with ui.row():
    with ui.tabs().classes('w-full').props(add="dense align=left") as tabs:
        one = ui.tab('Something')
        logs = ui.tab('Logs')
    ui.separator()

    with ui.tab_panels(tabs, value=one).classes('w-full').style('min-height: 268px'):
        with ui.tab_panel(one):
            ui.image('https://picsum.photos/id/377/640/360').style('max-width: 420px')
        with ui.tab_panel(logs):
            log = ui.log(max_lines=10).classes('w-full h-20')


with ui.row():
    ui.button('Log time', on_click=lambda: log.push(datetime.now().strftime('%X.%f')[:-5]))

ui.run()

In this example:

• run
• click on "Log time" button
• switch to the "Logs" tab - no entries here
• click again
• enties are visible

[falkoschindler]

Wow, thanks for reporting this issue, @marcin-koziol!

It seems like the log element doesn't exist before opening the tab. When I print its ID print(log.id) (→"13") and try to get the element from the JavaScript console getElement(13), it is undefined.

Right now I'm not sure how to fix it. When calling log.update() right after pushing new content, it works. But the main idea of ui.log was to not update the whole element for each new line. I guess there's a better way...

[marcin-koziol]

maybe we could add the ability to bind a variable to the log (same as for inputs), so we'll be able to push logs to this var , without having rendered component? Is the truncating logic implemented only on the client?

[falkoschindler]

Yes, the truncating logic is implemented on the client. But more importantly, we don't want to send the whole log of maybe thousands of lines to the client every time a new line is pushed. Instead we only want to send an incremental update. Therefore I'd like to avoid any fix or workaround involving log.update(), which would be called internally if would bind its content to some source.

[falkoschindler]

I still have no idea how to fix this issue. Therefore I'll remove the milestone for now.

[falkoschindler]

We have spotted a similar problem with AG Grids:

with ui.tabs().classes('w-full') as tabs:
    one = ui.tab('One')
    two = ui.tab('Two')
with ui.tab_panels(tabs, value=one).classes('w-full'):
    with ui.tab_panel(one):
        async def get_data():
            ui.notify(await grid.get_client_data())
        ui.button('Get data', on_click=get_data)
    with ui.tab_panel(two):
        grid = ui.aggrid({
            'columnDefs': [{'headerName': 'Name', 'field': 'name'}],
            'rowData': [{'name': 'Alice'}, {'name': 'Bob'}],
        })

Like with ui.log the UI element doesn't get mounted until the user visits the tab. How can we fix that?

[E-H-E-H]

Hi, just wondering, what is the best strategy for an workaround? , if you want multiple logs updating on multiple views? (for example on seperate pages, on multiple tabs, etc.)

[falkoschindler]

@E-H-E-H It shouldn't be a problem on separate pages. For the issue with ui.log inside hidden tabs I don't have any new ideas or workarounds...

But wait! Maybe we can re-implement ui.log with a much simpler approach. By simply adding labels to a scroll view, we can achieve a similar behavior which even works on hidden tabs:

import time
from typing import Optional
from nicegui import ui

ui.add_head_html('<style>.custom-log .q-scrollarea__content { padding: 0.25rem; gap: 0; }</style>')

class Log(ui.scroll_area):

    def __init__(self, max_lines: Optional[int] = None) -> None:
        super().__init__()
        self.classes('custom-log font-mono whitespace-pre-wrap bg-gray-50 border border-gray-200')
        self.max_lines = max_lines

    def push(self, text: str) -> None:
        with self:
            ui.label(text)
        while self.max_lines is not None and len(self.default_slot.children) > self.max_lines:
            self.remove(0)
        self.scroll_to(percent=100)

log = Log(max_lines=20)
log.push('Hello, world!')
log.push('Hello, world!')