Port #4173 to master: dashArray in Canvas

[IvanSanchez]

Allows using dashArray in <canvas> renderers.

[yohanboniface]

Worth a unittest?

[IvanSanchez]

@yohanboniface This is a graphical thing - in order to do unit tests for this we would need to do like Mapnik does, and compare screenshots to reference screenshots. Bit of an undertaking right now?

[yohanboniface]

Was just thinking about testing that the attributes are on the DOM element. But maybe that would be like testing browser Canvas implementation at the end…

[mourner]

Oh, I didn't even notice it was for stable previously...

[gommo]

We just found out that setLineDash isn't supported on IE10 and below so the code needs to check for that

[IvanSanchez]

@gommo Is there any workaround for IE10? According to https://msdn.microsoft.com/en-us/library/dn265063%28v=vs.85%29.aspx , it doesn't seem like it.

We might just need to note this down in the API docs for the dashArray option.

[gommo]

I'll need to add a change so we don't actually call setLineDash

[IvanSanchez]

@gommo Wait - does IE10 throw an error or something like that?

[gommo]

Yeah it does!

[IvanSanchez]

@gommo Then we need to fix this again!