[google_maps_flutter_web] Add "My Location" Widget

[nploi]

Currently, we don't "My Location" widget, so this PR i want support that feature, Thanks

Issue: flutter/flutter#64073

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[nploi]

small demo

demo-2.mov

[ditman]

Some comments, sorting in degree of importance (IMO):

• Use the watchPosition API so MyLocation automatically updates (instead of getCurrentPosition).
• Handle the case where users deny Geolocation permissions to the app, so the app doesn't crash or freeze awaiting for a Future/Stream that will never complete.
• Do not "hard-code" the translucent blue halo in the blue-dot.png, because that needs to be computed from the coords.accuracy value that the Geolocation API returns. Blue dot should be a blue circle with a white border and nothing more.
• Speaking of assets: make the mylocation-sprite-2x.png part of the assets of the package, and do not download it from a gstatic URL.
• Move (most of) the code to a separate src/my_location.dart file to not bloat the MapsController code, and also to make it easier to test. Pass parameters for the things that you need (like the gmaps.GMap or the MarkersController)
• Try to make the "loading" animation (and the "done" state) come from CSS, rather than using JS to build those animations (I provided a jsfiddle example).
• Some comments around naming that are completely subjective, but try to make the name of the method describe what's happening inside of it (for example, currently: _moveToCurrentLocation is a little bit weird)

Thanks for the contribution, very exciting to see this land!

[ditman]

This method will not update the user's location if they move around, unless something else on the map changes. I think this should use the watchPosition API, that returns a Stream<Geoposition> and then respond to the events from that stream. Some changes to this PR:

• If the user wants to render the MyLocation dot: subscribe to the watchPosition Stream, and on each Geolocation event update the Marker.
  • The first event of the watchPosition Stream can be used to remove the "waiting" animation class from the button, for example, and to get ready the marker that needs to be rendered.
• If the user wants to stop rendering their location, it's easy to remove whatever subscription to the Stream that we do, and whatever cleanup is needed.

Some documentation:

• See: https://api.dart.dev/stable/2.18.6/dart-html/Geolocation/watchPosition.html
• Async in Dart - Streams: https://dart.dev/tutorials/language/streams

[nploi]

Hi @ditman, can you help to review ?, i'm fixed some your comments, but there is a comment i will fix it in the next pr because this pr is too big to review :D.

[stuartmorgan-g]

Update from triage: this in on @ditman's radar, but there's been high-priority work in another plugin that has taken precedence.

[nploi]

Update from triage: this in on @ditman's radar, but there's been high-priority work in another plugin that has taken precedence.

@stuartmorgan Thank you for letting me know.

[stuartmorgan-g]

We've just completed the migration of the plugin code to the flutter/packages repository, as described in https://flutter.dev/go/flutter-plugins-repo-migration, and this repository is now being archived. Unfortunately that means that all in-progress PRs here must be moved to flutter/packages.

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Our apologies that your PR was caught in this one-time transition. We're aware that it's disruptive in the short term, and appreciate your help in getting us to a better long-term state!