Versatile clipping

[kurkle]

This PR changes the default clipping so it will clip at chartArea edge, if the scale defining that edge is limited at that end (by ticks.min/ticks.max). If min/max is not defined, the current clipping rules apply (borderWidth / 2 outside chartArea)

Overriding this clipping is also allowed per dataset:

clip: 10 // would clip 10px outside chartArea on each edge
clip: -10 // would clip 10px inside chartArea on each edge
clip: false // would not clip
clip: 0 // would clip to chartArea
clip: { left: 10, right: -10, top: false, bottom: 0) // per edge config

Fixes: #6631

TODO

• documentation
• clipping in core, enabling for any dataset type

Thoughts?

[benmccann]

Does this draw the image from #6631 (comment) ?

[kurkle]

Yes, by default.

[kurkle]

Updated the description.

[benmccann]

@kurkle I notice this is still in draft mode. Are you ready for us to review?

[kurkle]

Yeah, was waiting on CC/CI and got carried away in the mean time :)

[benmccann]

I'm surprise the default is false instead of null or undefined

[kurkle]

Default is false only for controllers not overriding getMaxOverflow
false meaning no clipping. Because the clipping could be off on one edge only, false is tested and clipping area extended to that edge of canvas.

[benmccann]

@kurkle looks like this one will need to be rebased

[kurkle]

Updated the fixtures to reflect the removal of zeroLine* functionality.
The grids are intentionally visible in these, to make the tests easily understandable.

Just chartArea borders would suffice, but I don't think thats currently (easily) doable.