Toolbox opens when clicking below all categories first time

[hannahbergam]

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Description

If you click below the categories within the toolbox, the toolbox opens with the first category selected. This only happens the first time (if you click again, it closes the toolbox, and if you click a third time, nothing happens).

Reproduction steps

1. Click in toolbox below all the categories and the toolbox opens with the first category selected

Stack trace

Screenshots

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Browsers

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[BenHenning]

This can be toggled, and is a side effect of us not being able to to distinguish why the toolbox now has focus (that is, whether it's from clicking or tab navigation). Here's a quirky repro of the bug that I sometimes do when I'm waiting for something:

Screen.recording.2025-07-02.12.26.07.PM.webm

Actually distinguishing between the two types of focus is probably difficult. Some other options we could consider:

• Add click handling to the toolbox with disabled propagation so that clicks don't change focus without explicit calls to focusNode like is done today with gestures.
• Make it so that clicking always opens the flyout but doesn't toggle it closed (this is technically an addition to the previous point).
• Try to fix the bug that causes the toggling: there is an actual issue happening with the second click that then closes the flyout. I think it's a consequence of how toolbox handles its getRestoredFocusableNode function.

[BenHenning]

Ah, actually I'm wrong. This is the line causing the problem:

https://github.com/google/blockly/blob/5acd072f0519f61848d86b148bdd44537fec9c0f/core/toolbox/toolbox.ts#L267

That causes the second click to then close the flyout. The toolbox still retains focus at this point, so clicking a third time won't reselect an item (since one is already selected), thus the flyout stays closed.

I suspect we can get rid of a lot of the hide chaff logic for toolbox, actually, since the focus system handles it automatically. However, this would be a deliberate behavior change of keeping the toolbox's flyout open when clicking on the toolbox again, rather than closing its flyout (which was v11 behavior, I believe, based on past testing and how the code is written).