User puck rotation should account for horizontal content insets

[1ec5]

When tracking the user’s course, UserCourseView’s arrow points in a direction determined by a CLHeading object, assuming that UserCourseView is located above the visual center of the map view, and that map’s vanishing point is located directly above UserCourseView. When the map view has a left or right content inset, the route line and UserCourseView are shifted to the side, while the map’s vanishing point remains horizontally centered due to mapbox/mapbox-gl-native#12728.

For example, in CarPlay, there is a wide content inset on the driver’s side to accommodate maneuver panels. When both the route and the user go due north, the route line is slanted towards the driver’s side while UserCourseView’s arrow nonetheless points straight up.

The 3D transform for UserCourseView’s arrow needs to account for horizontal content insets. The correction might end up depending on the pitch. As with mapbox/mapbox-gl-native#5245, it may be necessary to fudge the transform matrix’s m34.

/cc @mapbox/navigation-ios @d-prukop

[1ec5]

As with mapbox/mapbox-gl-native#5245, it may be necessary to fudge the transform matrix’s m34.

This would be the most correct fix, but for this issue it’s sufficient to just adjust the puck’s rotation without worrying about the rest of the transform matrix. We’re only talking about the rotation of a single shape, and the puck looks weird anyways when it isn’t a circle. Fixing that broader issue would require mapbox/mapbox-gl-native#10498 or even mapbox/mapbox-navigation-ios-examples#9.

[1ec5]

The more fundamental issue is that the map view’s vanishing point remains in the logical center instead of shifting to accommodate the content insets. That is, the arrow is pointing in the right direction, but the map has the wrong perspective. For example, this segment of the route line goes straight ahead until the maneuver, so it should be a vertical line on the screen instead of being slanted:

The most common workaround is to extend the opposite side of the map view off the right side of the screen to counterbalance the left content inset.