Allow more flexibility of painting of `Polygon` 'label'

[viskimark]

What do you want implemented?

• Check if there is already an open or closed issue that is similar to yours
• Ensure that you're using the latest version of flutter_map
• Ensure that you've read the documentation (both the website and API docs) thoroughly

Hello!

Is there any way to make it so we can give the labels of Polygons outlines? (Either as a parameter, or by making the label a Widget type, so we could use the workaround method as specified in https://api.flutter.dev/flutter/painting/TextStyle-class.html)

If there already is a workaround to this, please let me know aswell!

What other alternatives are available?

No response

Can you provide any other information?

No response

[JaffaKetchup]

This is not possible at the moment, because the text is painted onto the canvas (it isn't a widget).

The options are to add the option into the painter - but this is a niche option so it would probably be better to expose some sort of custom callback to account for other people's more niche requirements than we can think of.

Alternatively, and I have no idea how well it would work, you could try putting other transparent polygon over the current one, with the same label and outline text style. As long as the polygons share the same position, the labels should always appear one behind the other I think.

[viskimark]

Hi!

Thanks for the response, i wanted to do a follow-up:
I tried your workaround suggestion, and the results are surprisingly good.
I was expecting a big performance hit by duplicating all the polygons (of which i have a lot of on my map), but i didnt actually notice any negatives in this regard.
It works pretty much like i wanted it to.

(Im also an idiot because first i wanted to complain that the regular polygons color obstructs the label outline, then i realised i can just give the bottom polygon the color :D)
I'll keep the issue open for a bit, in case anyone else has some more insight, but im pretty sure from the quick testing, that this solution works for me.

[JaffaKetchup]

That's great, glad it worked out (at least for a fewer number of polygons) :)

[monsieurtanuki]

Would providing a List<TextStyle> instead of a TextStyle? do the trick?

[viskimark]

I dont know how flutter_map implements the label, but if for each TextStyle in the list a new Text widget would be created (as specified in the flutter docs i linked above), then i think it would indeed work.

[JaffaKetchup]

It would be a big breaking change, but I'm wondering whether we could expose a callback where the user can paint whatever they want into the polygon (with the origin at the calculated center). Then have a predefined callback which paints a label.

Might be overkill though. And not sure about performance. So using a list of styles probably does the trick for now.

[JaffaKetchup]

(I did also just realise that a user can always use the label positioning calculators themselves and use a MarkerLayer to display arbitrary 'labels'. Although the calculators do expect Polygons - a bit of an oversight on my part, but not too difficult to work with. Or you could go straight to the source and use the dart_polylabel2 library.)

[JaffaKetchup]

Ok, I'm going to close this as no longer for consideration. There's two/three good methods:

• As I first suggested, using multiple overlaid polygons - although this may not be very performant
• Using a marker with the label positioning calculators or directly with 'package:dart_polylabel2'

I think using a list of text styles doesn't provide enough flexibility. Adding a callback is a viable option - but option 2 is very similar.

I was a bit short-sighted in making the label position calculators accept Polygons rather than List<LatLng>. I was allowing future/external implementations to depend on the styling of the polygon, if that was important, but I don't think it could/should be. But if using the marker method and polygons, then it probably doesn't matter since the polygons need to be constructed anyway.