[Interest] QtLocation MapPolyLine and MapPolyGon style

maitai maitai at virtual-winds.org
Tue Feb 26 18:45:05 CET 2019

Thanks Paolo for your replies here and at qt bugs report

In fact I am porting a qt widget application based on QGraphicsScene to 
QML and indeed these painting features are badly missing. Calculating 
polygon/shapes screen coordinates is not an issue in itself but that 
will become really tricky to implement when the users pans or zoom, so I 
would say unless I can do it through mapboxgl I will have to propose 
something else than dashed areas and lines.

There are some other features which I think will be missing too, for 
instance lines are just "loxodromic" (rhumb) lines, when they should be 
"orthodromic" (great circle), or at least there should be an option for 
both cases. Another big issue is the projection. Mercator is OK in most 
cases but is there a way to have another projection (with mapboxgl maybe 
?), for instance Lambert conformal conic projection for usage in high 

That being said Qt Location is much much better that QGraphicsScene for 
doing all that stuff, of course.

Thanks again,
Philippe Lelong

Le 26-02-2019 15:21, Paolo Angelelli a écrit :
> If you need dashed or dotted or styled lines, at the moment that's the
> only workaround we can offer.
> The built-in lines are using QTriangulatingStroker under the hood,
> that seems to be missing that part
> of the QPen features (brush, style).
> as for map polygon, the only workaround i can think of, if mapboxgl
> does not offer it/is not an option, is
> to use a MapQuickItem instead, create the polygon with Shapes, and
> then do the math and georeference it "manually".
> As for your last question, i don't think i can answer since too many
> details are missing
> hope this helps a bit, anyway
> On Mon, 25 Feb 2019 20:01:17 +0100
> maitai <maitai at virtual-winds.org> wrote:
>> Hi,
>> I may be wrong since it seems incredible, but it seems there is no way
>> to draw a MapPolyLine dashed or dotlined, and similarly I didn't find 
>> a
>> way to fill a MapPolygon with a pattern.
>> If that is the case, what in your opinion would be the best way to
>> implement this?
>> I found QTBUG-46651 which recommends to use an empty mapboxgl layer
>> instead of my current itemsoverlay map, would that cover the needs 
>> since
>> I have plenty of other mapItems and need to manage z values for each 
>> of
>> them?
>> Thanks
>> Philippe Lelong.
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