PR: Greatly improve Outline performance and update it correctly when it becomes visible

[ccordoba12]

Description of Changes

• Simplify and greatly speed up updating trees when new symbols arrive from PyLSP. For instance, this decreases the time necessary to update the tree of our codeeditor.py file from 700 ms to 30 ms in my laptop.
• Update trees when the Outline is undocked, but not if its window is minimized.
• Avoid the Editor plugin to update the current tree when given focus (this was very inefficient).
• Dock plugins if they are undocked before hiding them when going to the Panes > View menu. I discovered that UX bug while working on this PR.
• Add a test to check that we update (don't update) the Outline when it becomes visible (is not visible) under different circumstances.

Issue(s) Resolved

Fixes #16634

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[dalthviz]

Thanks @ccordoba12 ! Seems like things are working as described in the OP 👍

However, regarding the issue of the undocked panes not respecting the selection on the View Panes menu, we shouldn't instead of docking the pane, save the window pane geometry and restored it when checking the pane entry again from the menu (keeping the undocked panes state)?

Also, while checking this, I noticed another issue related with maximizing the Editor action and the Outline pane state on the View > Panes menu. Seems like although the Outline is being showed along side the Editor (being the Outline previously not visible), the checkbox state for the Outline is not showing is visible. I think this is not caused by the changes done here but maybe could be worthy to fix it here?

[ccordoba12]

However, regarding the issue of the undocked panes not respecting the selection on the View Panes menu, we shouldn't instead of docking the pane, save the window pane geometry and restored it when checking the pane entry again from the menu (keeping the undocked panes state)?

That's a very interesting idea! And something that will bring cool interactions in Spyder, like showing certain plugins on demand out of the main window. In other words, if users hide a plugin by going to View > Panes while it's undocked, and then press the shortcut to show it, with your suggestion it'd be displayed as undocked again.

I started to work on this idea but I think we'd need to differentiate between the Dock (bring back to the main window) and Close (hide) actions when the plugin is undocked for users to make sense of it. So I think it's work for another PR because my proposed fix is really simple but what you suggest would require things out of the current scope of this PR.

Seems like although the Outline is being showed along side the Editor (being the Outline previously not visible), the checkbox state for the Outline is not showing is visible. I think this is not caused by the changes done here but maybe could be worthy to fix it here?

That's a good point too, but we could discuss how to solve it (or even if we should show the Outline next to the Editor) when we're migrating the editor to the new API. What do you think?

[dalthviz]

Then I think we need to create follow-up issues for both things for further discussion: the behavior when an undocked pane is requested to be hidden and the coherence between the Panes menu checkboxes and the maximize action (mostly for the Editor case where also the Outline is shown)

[ccordoba12]

the behavior when an undocked pane is requested to be hidden

See PR #19784. I'll rebase and finish it after this one is merged.

the coherence between the Panes menu checkboxes and the maximize action (mostly for the Editor case where also the Outline is shown)

Instead of opening a new issue, I posted #16265 (comment) because precisely tracking if the Outline is visible when the Editor is maximized would help us to solve that issue in an intuitive way.

[ccordoba12]

Note: I decided to rebase this PR in order to re-run our tests and check that everything is green, given that it's almost a month old.

[ccordoba12]

@dalthviz, this should be ready to be merged, unless you have further comments.