[FEATURE] Covert LatLng to Point with map rotation in mind

[mohammedX6]

What do you want implemented?

I want to covert a LatLng to point with taking care map rotation

minimal example of the problem I have https://filebin.net/t8uftfm4aklz69yx/minimal_example.zip

What other alternatives are available?

I tried this but the result is wrong

 @override
  CustomPoint? latLngToPoint(LatLng localPoint) {
    if (_state.originalSize == null) {
      return null;
    }

    final width = _state.originalSize!.x;
    final height = _state.originalSize!.y;

    var pos = _state.options.crs.latLngToPoint(localPoint, _state.zoom);

    final localPointCenterDistance =
        CustomPoint((width / 2) - pos.x, (height / 2) - pos.y);

    var mapCenter =
        _state.options.crs.latLngToPoint(_state.center, _state.zoom);
    var point = mapCenter - localPointCenterDistance;

    if (_state.rotation != 0.0) {
      point = point - _state.getPixelOrigin();
      point = rotatePoint(mapCenter, point);
    }


    return point;
  }

Can you provide any other information?

No response

Platforms Affected

Android, iOS

Severity

Obtrusive: No workarounds are available, and this is essential to me

Requirements

• I agree to follow this project's Code of Conduct
• I am using the latest stable version of this package
• I have checked for similar feature requests which may be duplicates

[ibrierley]

Whats your test case you are trying to do ?

[mohammedX6]

Whats your test case you are trying to do ?

Hi
I am trying to create a magnifier for the map, The magnifier needs the tap position, everything is ok but if the map is rotated the tap position is wrong.

Take a look here

[JaffaKetchup]

Hi @mohammedX6, I have a better understanding now.

The onTap callback within MapOptions gives a LatLng point, but also a TapPosition, which provides the actual screen position, both relative to the widget (relative), or relative to the screen (global). It should work regardless of map rotation.

For example, use:

MapOptions(
  onTap: (screenPoint, _) {
    print(screenPoint.relative);
    print(screenPoint.global);
  }
),

Let me know if this works for you!

[mohammedX6]

@JaffaKetchup Thanks for response, I am using flutter_map_line_editor onDragUpdate callback , using the screenPoint.global The result is much better now, But there is some offset as you can see in the picture
The blue circle is the current active drag position but the red circle is the wrong postion.
I think I need to subtract the position to the screen center?

[JaffaKetchup]

Maybe? There might be some weird anchoring going on, if you're using markers.

[mohammedX6]

no markers involved.

[JaffaKetchup]

Where are the red circle and blue circles supposed to be?

[mohammedX6]

the red circle must be in the same location as the blue circle.
The blue circle is the point that I am currently dragging.

[JaffaKetchup]

Not really sure in this case. The position from onTap is coming from a dependency, and is correct from my testing, so there must be something else wrong.

[mohammedX6]

I think I might dig more into the code, Anyway thanks @JaffaKetchup .

[mohammedX6]

@ibrierley Hi, here is an issue I opened,
Anyone can use this minmial example to understand the problem I have
https://filebin.net/t8uftfm4aklz69yx/minimal_example.zip

[ibrierley]

ok, that isn't a minimal example. But in the meantime, WHY do you want latLngToPoint. Just checking you're not trying to reinvent the wheel. (I'm not suggesting at some point there shouldn't be a method for this..but trying to understand why firstly).

For example, if you have a LatLng, why not just place a Marker there with any widget you want ? Does it need to be outside of FlutterMap or something ?

[mohammedX6]

@ibrierley YES that's exactly what i want.

[ibrierley]

I suspect this isn't easily going to happen unless someone has a lot of time and/or been working on this already. I think there's probably too many variables that one can't be confident of and change when a rotation happens.

Maybe someone will have a brainwave though!

There's also the question of what space one wants the result in...in map widget space, in an outer widget space, or screen resolution space.

So my interim suggestion would be either a) don't allow rotation in the app, or b) make sure everything is done in flutter_map layer coordinate space (eg as a marker widget, I would suspect this is easiest), or c) spend a lot of time hacking something together.

[ibrierley]

Actually, this may be possible if we reverse the rotationPoint...and use a pre rotated pixel origin....something like...

@override
  CustomPoint latLngToScreenPoint(LatLng latLng) {

    var pxo = (_state.project(_state.getCenter(),zoom) - _state.originalSize! / 2.0).round();

    var point = _state.options.crs.latLngToPoint(latLng, _state.zoom);

    final mapCenter =
    _state.options.crs.latLngToPoint(_state.center, _state.zoom) ;

    if (_state.rotation != 0.0) {
      point = rotatePoint2(mapCenter, point);
    }

    return  point - pxo;
  }

CustomPoint<num> rotatePoint2(
      CustomPoint<num> mapCenter, CustomPoint<num> point) {
    final m = Matrix4.identity()
      ..translate(mapCenter.x.toDouble(), mapCenter.y.toDouble())
      ..rotateZ(_state.rotationRad)
      ..translate(-mapCenter.x.toDouble(), -mapCenter.y.toDouble());

    final tp = MatrixUtils.transformPoint(
        m, Offset(point.x.toDouble(), point.y.toDouble()));

    return CustomPoint(tp.dx, tp.dy);
  }

Maybe a little messy, but I've run out of time though for today.

[mohammedX6]

@ibrierley MAN, THIS THING IS WORKING LIKE A CHARM !,
You are genius
Where I can give a small gift like a donation or something?

[ibrierley]

Thanks for the feedback, I'll try and get a PR sorted this weekend for it (maybe with renaming the rotate functions so they're clearer), so it ends up in the main code. We don't have a Flutter_map donation thing yet (maybe that could be a discussion, not sure if we want to stay away from that or not). Normally devs will have a donation button on their respective repos though on Git if people feel flush tho ;).

[JaffaKetchup]

We probably should setup an overall donation thing.
I've already got a GitHub Sponsors verified account now, and if you got one too (not difficult), GitHub allows us to add a button to this repo, and both of our names would be listed separately. This means people can donate to one or both of us freely.
I have this setup in my main repos if you want to have a look.

[mohammedX6]

Thanks for the feedback, I'll try and get a PR sorted this weekend for it (maybe with renaming the rotate functions so they're clearer), so it ends up in the main code. We don't have a Flutter_map donation thing yet (maybe that could be a discussion, not sure if we want to stay away from that or not). Normally devs will have a donation button on their respective repos though on Git if people feel flush tho ;).

@ibrierley
I don't see a donation button on your page, Can you send Ko-fi or PayPal donation link?

[ibrierley]

Trying to avoid spamming here, but I think you were using https://github.com/ibrierley/flutter_map_line_editor and look halfway down.

…

On Fri, Jul 29, 2022 at 12:06 PM Mohammed Aljezawi ***@***.***> wrote: Thanks for the feedback, I'll try and get a PR sorted this weekend for it (maybe with renaming the rotate functions so they're clearer), so it ends up in the main code. We don't have a Flutter_map donation thing yet (maybe that could be a discussion, not sure if we want to stay away from that or not). Normally devs will have a donation button on their respective repos though on Git if people feel flush tho ;). @ibrierley <https://github.com/ibrierley> I don't see a donation button on your page, Can you send Ko-fi or PayPal donation link? — Reply to this email directly, view it on GitHub <#1311 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AA5YN5MXN2STWZKGPTU4LCDVWO3KDANCNFSM5344UA6A> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[ibrierley]

There's now a PR at #1325 if you wanted to test that.

[mohammedX6]

I am confirmed it's working.

[JaffaKetchup]

Fixed as of v2.2.0. Thanks for the report!