Log console status bar widget does not update

[jasongrout]

Description

Log console status bar widget sometimes does not update its message count

Reproduce

On JupyterLab 1.2.0a1:

1. Open a new notebook
2. Open the Log Console and add a few timestamps so that there are some messages
3. Observe that the message count in the status bar is updated
4. Open a new launcher (not a notebook, just the launcher)
5. Notice that when the launcher is focused, you still see the notebook's message count.

Expected behavior

In step 4, the message count should display zero messages.

Context

• Operating System and version: macOS 10.14.6
• Browser and version: Firefox 69
• JupyterLab version: 1.2.0a1

CC @mbektasbbg

[adityar-r]

Can you help me find the log console of step 2, I am unable to find it.

[jasongrout]

You can open it from the view menu or by clicking on the message icon in the status bar.

[mbektas]

@jasongrout the reason for this behavior is, active source is updated when a new notebook is activated (https://github.com/jupyterlab/jupyterlab/blob/master/packages/logconsole-extension/src/index.tsx#L540) or a notebook is closed (https://github.com/jupyterlab/jupyterlab/blob/master/packages/logconsole-extension/src/index.tsx#L553).

I couldn't find a way to detect deactivation of a notebook/log source.

Is there a way to listen for deactivation of a notebook (or activation of another tab that is not a notebook)?

[jasongrout]

Good question. You could handle this similar to how the line numbers are handled in the status bar, and listen to the currentChanged signal on the lab shell:

jupyterlab/packages/statusbar-extension/src/index.ts

Lines 228 to 241 in e04e3af

	labShell.currentChanged.connect((_, change) => {
	const { oldValue, newValue } = change;
	// Check if we need to disconnect the console listener
	// or the notebook active cell listener
	if (oldValue && consoleTracker.has(oldValue)) {
	(oldValue as ConsolePanel).console.promptCellCreated.disconnect(
	onPromptCreated
	);
	} else if (oldValue && notebookTracker.has(oldValue)) {
	(oldValue as NotebookPanel).content.activeCellChanged.disconnect(
	onActiveCellChanged
	);
	}