Add clipping for rotated/tilted Map Items

This patch adds proper rotation/tilting support to Map Items.
To do so, clipping is now performed in wrapped mercator space
instead of screen space.
This prevents projection of geo coordinates that ended behind
the camera, and that would be projected incorrectly by the
projection transformation.

This patch therefore does not use the screen clipping code
any longer (clipPathToRect), since the geometry has already
been clipped.
The downside is that updateSourcePoints is now necessary for
any viewport change.

This would be necessary anyway in presence of tilt or rotation.

NB: Handling of MapQuickItems with zoomLevel set is still TODO.

Future work:
1) Optimize updateSourcePoints by pre-computing the mercator
projection of the geometry, and let updateSourcePoints do only
the wrapping/clipping/projection-to-screen operations.

2) Remove updateScreenPoints altogether

Change-Id: Ie0d3dbef68d48ac97a596d40240d0ac126c0efaf
Reviewed-by: Alex Blasche <alexander.blasche@qt.io>
Reviewed-by: Paolo Angelelli <paolo.angelelli@qt.io>
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

1 files changed, 10 insertions, 2 deletions

diff --git a/src/positioning/positioning.pro b/src/positioning/positioning.pro
index c4c9cc6c..0df56a71 100644
--- a/src/positioning/positioning.pro
+++ b/src/positioning/positioning.pro
@@ -1,6 +1,10 @@
 TARGET = QtPositioning
 QT = core-private
 
+#INCLUDEPATH += ../3rdparty/poly2tri
+INCLUDEPATH += ../3rdparty/clipper
+INCLUDEPATH += ../3rdparty/clip2tri
+
 QMAKE_DOCS = $$PWD/doc/qtpositioning.qdocconf
 OTHER_FILES += doc/src/*.qdoc   # show .qdoc files in Qt Creator
 
@@ -53,7 +57,8 @@ PRIVATE_HEADERS += \
                     qpositioningglobal_p.h \
                     qlocationdata_simulator_p.h \
                     qdoublematrix4x4_p.h \
-                    qgeopath_p.h
+                    qgeopath_p.h \
+                    qclipperutils_p.h
 
 SOURCES += \
             qgeoaddress.cpp \
@@ -78,9 +83,12 @@ SOURCES += \
             qgeopath.cpp \
             qlocationdata_simulator.cpp \
             qwebmercator.cpp \
-            qdoublematrix4x4.cpp
+            qdoublematrix4x4.cpp \
+            qclipperutils.cpp
 
 HEADERS += $$PUBLIC_HEADERS $$PRIVATE_HEADERS
 
 
 load(qt_module)
+
+LIBS_PRIVATE += -L$$MODULE_BASE_OUTDIR/lib -lclip2tri$$qtPlatformTargetSuffix()