Marble Qt KML gx:LatLonQuad Support

[Raven Tamara]

I would like to place an image on the map with anonrectangular
quadrilateral.
Does Marble support the KML tag gx:LatLonQuad?

I see there are source files and API documentation defining the LatLonQuad
class:
src\lib\marble\geodata\handlers\kml\*
src\lib\marble\geodata\data
https://api.kde.org/stable/kdeedu-apidocs/marble/html/classMarble_1_1GeoDataGroundOverlay.html
https://api.kde.org/stable/kdeedu-apidocs/marble/html/classMarble_1_1GeoDataLatLonQuad.html

However, I cannot seem to use it successfully
I built Marble (Qt version) on Windows 10 MSCV1900.
git clone -b Applications/19.08 https://github.com/KDE/marble.git
./marble/Marble-Src
cd ./marble/Marble-Build/Release
cmake -G "Visual Studio 14 Win64" -Wno-dev -DCMAKE_BUILD_TYPE=Release
-DCMAKE_INSTALL_PREFIX=..\..\Marble-Bin\Release ..\..\Marble-Src

Loading a KML and PNG into the marble-qt.exe does not display any image.
KML used:
<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://www.opengis.net/kml/2.2" xmlns:gx="
http://www.google.com/kml/ext/2.2">
<Folder>
<name>Slope Layer</name>
<open>1</open><GroundOverlay>
<name>Slope Layer</name>
<color>44ffffff</color>
<Icon>
<href>slope.png</href>
<viewBoundScale>0.75</viewBoundScale>
</Icon>
<gx:LatLonQuad><coordinates>18.858652,-34.043223 19.011842,-34.043246
19.011921,-33.916329 18.858793,-33.916149</coordinates></gx:LatLonQuad>
</GroundOverlay></Folder></kml>

KML reference:
https://developers.google.com/kml/documentation/kmlreference#gxlatlonquad
(Note, this KML works in Google Earth, so at least I know it is valid.)

 Likewise, using the C++ API produces no imagery:
...
   Marble::GeoDataCoordinates tl(18.858652, -34.043223, 0.0,
Marble::GeoDataCoordinates::Degree);
   Marble::GeoDataCoordinates tr(19.011842, -34.043246, 0.0,
Marble::GeoDataCoordinates::Degree);
   Marble::GeoDataCoordinates br(19.011921, -33.916329, 0.0,
Marble::GeoDataCoordinates::Degree);
   Marble::GeoDataCoordinates bl(18.858793, -33.916149, 0.0,
Marble::GeoDataCoordinates::Degree);

   Marble::GeoDataLatLonQuad quad;
   quad.setTopLeft(tl);
   quad.setTopRight(tr);
   quad.setBottomRight(br);
   quad.setBottomLeft(bl);

   Marble::GeoDataGroundOverlay *overlay = new Marble::GeoDataGroundOverlay;
   overlay->setLatLonQuad(quad);
   overlay->setIcon(QImage("slope.png"));

   Marble::GeoDataDocument *document = new Marble::GeoDataDocument;
   document->append(overlay);
   mapWidget->model()->treeModel()->addDocument(document);
...

Has it been deprecated or left out of master?
Does it matter if I build the KDE or Qt version?
Am I missing an optional package?
>From my cmake command:
-- The following OPTIONAL packages have not been found:
 * ZLIB, general-purpose lossless data-compression library, <
http://www.zlib.net/>
   When found, system zlib is used. When not found, a Marble internal zlib
is used.
 * Phonon4Qt5, Qt-based audio library, <https://phonon.kde.org/>
   Support for playback of soundcue elements
   Voice navigation (sound or human speakers)
 * libgps, communicating with the GPS daemon, <http://catb.org/gpsd/>
   position information via gpsd
 * libwlocate, WLAN-based geolocation, <http://www.openwlanmap.org/>
   Position information based on neighboring WLAN networks
 * libshp, reading and writing of ESRI Shapefiles (.shp), <
http://shapelib.maptools.org/>
   reading and displaying .shp files
 * ECM (required version >= 1.7.0)

P.S. Also, I receive the following warning when using -DKF5=TRUE:
CMake Warning:
  Manually-specified variables were not used by the project:

    WITH_KF5
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