Clicking on tab stops click event propagation

[MetRonnie]

Description

Clicking on a tab in a tab bar does not cause in-DOM context menus to close etc.

Reproduce

1. Open something that depends on a click outside event to close, e.g. a Jupyter Lab context menu
2. Click on a tab title
3. The context menu remains open

Expected behavior

The context menu closes

Context

• Operating System and version: Windows 11
• Browser and version: Chrome 138, Edge 138
• JupyterLab version:
  @lumino/default-theme: 2.1.10
  @lumino/widgets: 2.7.1

Troubleshoot Output

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Command Line Output

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Browser Output

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[sccolbert]

Confirmed. The popup menus are rendered at the root document node with the highest precedence and trap all mouse events before they go elsewhere. This "should" be a simple detection of the mousedown event in the menu handler to see if it is outside the menu bounds. The timers on the submenus muddy the waters a bit. I'll look into it.

[MetRonnie]

Note this has not been fixed by #818, which only changed the behaviour of Lumino menus but did not fix the tab click stopping event propagation which means third party menus etc still do not close when clicking tabs.