Introduce Widget D&D with Magicline internals under the hood

[Olek Nowodziński]

The basic idea is to reuse magicline's engine to visually mark valid places to drop a block widget while the mouse is moving.

[Olek Nowodziński]

Created branches ​t/10933 (dev) and t/10933 (tests).

[Frederico Caldeira Knabben]

Just to not forget about it... we cannot pass this code with the "magicfinger" name. The final name must be chosen and the core properly changed.

[Olek Nowodziński]

Replying to fredck:

Just to not forget about it... we cannot pass this code with the "magicfinger" name. The final name must be chosen and the core properly changed.

How about "lineutils"?

[Frederico Caldeira Knabben]

Replying to a.nowodzinski:

How about "lineutils"?

I'm fine with it... I'm not able to say it, but it works well when read :D

[Piotrek Koszuliński]

Pushed t/10933 on dev with minor code fixes.

Still:

• There will be no revert() calls in tests if they failed.
• Finder#traverseSearch uses cache which is shared between all instances. Most likely this is incorrect.
• Callback functions are repeating in Liner constructor.
• Lookups in widget/plugin.js are defined in natural lang.
• removeListeners in onBlockWidgetDrag is defined in the middle of nowhere.
• Last two listeners in onBlockWidgetDrag use exactly the same callback.

[Olek Nowodziński]

Replying to Reinmar:

Pushed t/10933 on dev with minor code fixes.

Still:

• There will be no revert() calls in tests if they failed.
• Finder#traverseSearch uses cache which is shared between all instances. Most likely this is incorrect.
• Callback functions are repeating in Liner constructor.
• Lookups in widget/plugin.js are defined in natural lang.
• removeListeners in onBlockWidgetDrag is defined in the middle of nowhere.
• Last two listeners in onBlockWidgetDrag use exactly the same callback.

I improved the code referring to your concerns. Happy reviewing ;>

Magicfinger is now Lineutils.

[Piotrek Koszuliński]

I pushed one commit to dev and amended one commit in tests (the last one).

Everything seems to work fine except undo after dnd. I reported #11098.

[Olek Nowodziński]

Feature landed in major ​git:ca5b94a and tests 31e7be5.