Allow ability to define style cycles for Draw tools

[philippjfr]

This PR allows adding style cycles to the PolyDraw stream (but this could be expanded to the other draw streams). As an example here we cycle over the fill_color and line_width of the drawn polygons:

poly = hv.Polygons([[(2, 2), (5, 8), (8, 2)]])

poly_stream = streams.PolyDraw(source=poly, drag=True, show_vertices=True,
                               style_cycles={'fill_color': ['red', 'green', 'blue'],
                                             'line_width': [3, 5, 10]})

poly

• Fixes PolyDraw stream addition to allow setting an additional variable to color polygon #2694
• Expand to BoxEdit and FreehandDraw tools
• Add example in documentation

[jbednar]

Looks great! Does it need to be style_cycles, or could it just be styles, which are cycled if they are cycles and otherwise just applied? Just brainstorming; not sure which approach is better.

[philippjfr]

Looks great! Does it need to be style_cycles, or could it just be styles, which are cycled if they are cycles and otherwise just applied? Just brainstorming; not sure which approach is better.

It could just be styles I suppose, that is somewhat redundant since you can just set the style in the usual way but may be cleaner regardless.

[philippjfr]

@jbednar @jlstevens Let me know which you prefer, I'd be happy with accepting both lists (as cycles) and scalar values, and then call it simply styles.

[jbednar]

I'd vote for styles. Actually I vote for just respecting the usual style options set in the usual way and cycling if those are cycles, but I assume that's not feasible?

[jlstevens]

I also vote for keeping the API as consistent as possible. Why can't PolyDraw support the common style options for polygons which can then be set with styles or constants?

[philippjfr]

Actually I vote for just respecting the usual style options set in the usual way and cycling if those are cycles, but I assume that's not feasible?

That's not consistent with the way cycles behave in HoloViews, styles cycle in an overlay but not within a single Polygons/Paths element.

Why can't PolyDraw support the common style options for polygons which can then be set with styles or constants?

I'm not following what your suggesting here, that's what the styles suggestion is no?

[jbednar]

styles cycle in an overlay but not within a single Polygons/Paths element.

Ah, that's the key issue here. Worth brainstorming if there is a way more general than this approach to achieve within-Element cycling.

[philippjfr]

if there is a way more general than this approach to achieve within-Element cycling.

That can now be done via dim style mappings but I don't see any way those could feasibly be implemented client-side.

[philippjfr]

I'm going to go ahead and rename it to styles and support scalar values. Respecting cycles within an element would be highly inconsistent so I vote against that.

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