Anchor position top/bottom wrong way around

[mjtalbot]

Firstly thank you, really enjoying the map!

The Anchor.top and Anchor.bottom look like they are the wrong way around, Anchor top actually pins the bottom of my marker to the correct spot.

Should be easy to verify, just place a few markers and zoom in and out.

[johnpryan]

Thanks for filing an issue! I think the original intention was that "top" meant "the top of the marker is pinned to the location." In Leaflet JS, the anchor is an X,Y position defining the "tip of the icon":

The coordinates of the "tip" of the icon (relative to its top left corner). The icon will be aligned so that this point is at the marker's geographical location. Centered by default if size is specified, also can be set in CSS with negative margins.

But it could be less confusing to define the anchor point as "below" and "above" the point on the map. Either way, we need better terminology or documentation for this feature.

[mjtalbot]

I could be totally misunderstanding something, but I think I agree with you, as in I also thought top would pin the top of the marker as well. However top pins the bottom of the marker to the geographical location.

Let me run through an example

Currently:

var pixelPosY =
              (pos.y - (markerOpt.height - markerOpt._anchor.top)).toDouble();

lets say the geographical y position is calculated to be at 10, and we have a 5x5 marker.

if the top anchor is selected, the top of the marker will be drawn at (10 - (5 - 0)) or 5.
the bottom of the marker is at the geographical y position

if the bottom anchor is selected, the top of the marker will be drawn at (10 - (5 - 5)) or 10.
the top of the marker is at the geographical y position.

I think it should be:

var pixelPosY =
              (pos.y - markerOpt._anchor.top).toDouble();

if the top anchor is selected, the top of the marker will be at (10 - 0), or 10.
the top of the marker is at the geographical location.

if the bottom anchor is selected, the top of the marker will be at (10-5) or 5.
the bottom of the marker is at the geographical y position.

[johnpryan]

There's been some changes to AnchorAlign since this issue, marking as stale