[QGIS-Developer] QGIS 3 - QgsPoint vs. QgsPointXY

[Nyall Dawson]

On 26 October 2017 at 07:30, Nyall Dawson <nyall.dawson at gmail.com> wrote:
> On 26 October 2017 at 02:09, C Hamilton <adenaculture at gmail.com> wrote:
>> Did the QGIS 3 API just go back to QgsPoint rather than the QgsPointXY for
>>
>> QgsGeometry.fromPolyline()
>
> Yes, see [1]. From the PR:

Oops - forgot the link: https://github.com/qgis/QGIS/pull/5418

Nyall

>
>
> "Rename QgsGeometry::fromPolyline as QgsGeometry::fromPolylineXY
> ...and add new QgsGeometry::fromPolyline which uses QgsPoint
>
> We want to encourage people not to use the QgsPointXY method, as it
> drops Z/M values. So it's moved across to a different name to make way
> for a new QgsGeometry::fromPolyline which uses a QgsPoint list instead
> of QgsPointXY, thus keeping Z/M values intact.
> Similarly, QgsPolyline now is a list of QgsPoint (keeping z/m values)
> and the old 2d QgsPolyline type was renamed to QgsPolylineXY.
> Making the QgsPoint method the "preferred" method and making
> linestrings just as easy to create from z/m dimensioned points as 2d
> points is important to push people to write code which does not
> discard these important dimensions.
>
> As a bonus, the QgsPoint methods are more efficient anyway, since they
> don't require creation of a temporary list."
>
> So you could do a quick change of fromPolyline -> fromPolylineXY. But
> if you're working with existing geometries/points, use the QgsPoint
> based fromPolyline instead, and all users with Z/M dimensioned data
> will thank you!
>
>> When do you expect to have the QGIS 3 API stable?
>
> No sooner than the final release... We'll be stuck with the 3.0 API
> for a LOOOOOONG time, so we need to ensure it's as good as we can get
> before we hit the final release deadline.
>
> Nyall