Palettes: Implement Type-Ahead Find with incremental search

[shoogle]

Resolves: no issue in tracker

If the user presses a letter key while in the Palettes tree then a matching palette or cell gains focus. E.g. Press 'L' to jump to the Lines palette.

Pressing multiple keys in quick succession enables incremental search. E.g. Press 'A' shortly followed by 'R' to skip Accidentals and go straight to Articulations.

Pressing the same key repeatedly cycles through matching items. E.g. 'T' => Time Signatures, 'T' => Text, 'T' => Tempo, 'T' => Time Signatures, etc.

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[MarcSabatella]

I know I can find out if I build this, but, what happens if I type "Treble" - do I get a treble clef, or does the "T" get "eaten" by the code jumpng to the time signature palette? Also, I assume this code is only active when not in the search box, so regular search behavior isn't affected?

[shoogle]

what happens if I type "Treble" - do I get a treble clef, or does the "T" get "eaten" by the code jumpng to the time signature palette?

If you are on the palettes then it will take you to a palette. If you are within a palette then it will take you to an item within that palette. In other words, you cannot type "treble" and expect to get a treble clef unless you are already in the clefs palette.

This is slightly different to how type-ahead find usually works in a tree view. Normally you are able to jump to other levels of the tree, but only if they have previously been expanded (i.e. you can jump to any item that is currently visible). I'm not sure how useful that behaviour is, especially given that we already have search to take you straight to an item.

See the template chooser in the New Score Wizard for an example of the conventional behaviour. Make sure the template tree has focus and not the searchbox.

Also, I assume this code is only active when not in the search box, so regular search behavior isn't affected?

Correct.

[anatoly-os]

@shoogle have you had a chance to test this PR on macOS and Windows? Focus doesn't work for me on macOS as you explained in the description of this PR. Typing "L" doesn't make "Lines" palette focused.

[shoogle]

@anatoly-os, I've only tested on Windows so far and it worked there. I will try on Linux and macOS.

[shoogle]

@anatoly-os

Typing "L" doesn't make "Lines" palette focused.

I tested on macOS and it worked for me. However, it is possible that 'L' was being swallowed by an application shortcut (i.e. if you defined one in Preferences). If that's the case then the latest commit should fix it.