t/ckeditor5/416d: Implemented automatic items grouping in the ToolbarView component

[oleq]

Suggested merge commit message (convention)

Feature: Implemented automatic items grouping in the ToolbarView component. Closes ckeditor/ckeditor5#416.

BREAKING CHANGE: The internal structure of the component has changed. Toolbar items are no longer direct descendants of the toolbar in DOM, which may affect some integrations (mainly CSS selectors if adjustments were made to the styles).

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Additional information

Requires:

• t/ckeditor5/416d: Created a "three vertical dots" icon ckeditor5-core#196 (icon)
• t/ckeditor5/416d: Implemented the getResizeObserver() helper ckeditor5-utils#303 (resize observer API)
• t/ckeditor5/416d: Enabled automatic items grouping  ckeditor5-editor-classic#99 (use-case)
• t/ckeditor5/416d: Enabled automatic items grouping  ckeditor5-editor-decoupled#44 (use-case)
• T/ckeditor5/416d: Adjusted toolbar styles to allow automatic items grouping ckeditor5-theme-lark#243 (styles)

Constellation for testing and development.

[oleq]

Some concerns:

• We may need throttling on top of the ResizeObserver,
• ...?

[oleq]

@Mgsy Could you check the constellation and play with the new feature a little bit? There's a manual test ready but also all ClassicEditors and DecoupledEditors in docs should have it enabled.

[jodator]

The same bug with Chrome rendering problems :( I'm not reporting this as I feel that we track that already.

[jodator]

This is a bug or a feature? 😃

[jodator]

Might be a follow-up: I cannot type after executing a command.
Steps:

1. Use alt+f10 to focus toolbar
2. Navigate to overflow menu
3. execute some command

Actual (focus is lost)

Expected (focus is somewhere - like in normal toolbar)

[jodator]

ps. the very, very, very long toolbar is lost on the other side ;)

[jodator]

Some minor things detected. I couldn't find anything in particular that should needed to be changed. The code looks OK.

I also find some minor issues with the behavior but nothing blocking though (maybe except that execute on overflowed toolbar).

[oleq]

The same bug with Chrome rendering problems :( I'm not reporting this as I feel that we track that already.

Yes.

This is a bug or a feature? 😃

Never planned this but this is definitely a feature 😛

Might be a follow-up: I cannot type after executing a command.

It's a general issue. I added a comment explaining the scope of the problem.

ps. the very, very, very long toolbar is lost on the other side ;)

Yup. Created a follow-up.