Add method to QgsAbstractGeometry to convert geometry to QPainterPath

Unlike QgsGeometry::asQPolygonF, this allows for correct handling of multipolygons and rings, etc. And potentially, the generated QPainterPaths could use arc segments instead of segmentizing geometries. In fact, there's been disabled code which seems to do this in place since the new geometry engine was introduced back in 2.10! TODO: check if this code works correctly...
qgis · Jul 3, 2020 · 205273e · 205273e
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diff --git a/python/core/auto_generated/geometry/qgsabstractgeometry.sip.in b/python/core/auto_generated/geometry/qgsabstractgeometry.sip.in
@@ -318,6 +318,18 @@ Similarly, m-values can be scaled via ``mScale`` and translated via ``mTranslate
 Draws the geometry using the specified QPainter.
 
 :param p: destination QPainter
+%End
+
+    virtual QPainterPath asQPainterPath() const = 0;
+%Docstring
+Returns the geometry represented as a QPainterPath.
+
+.. warning::
+
+   not all geometry subclasses can be represented by a QPainterPath, e.g.
+   points and multipoint geometries will return an empty path.
+
+.. versionadded:: 3.16
 %End
 
     virtual int vertexNumberFromVertexId( QgsVertexId id ) const = 0;

diff --git a/python/core/auto_generated/geometry/qgscurve.sip.in b/python/core/auto_generated/geometry/qgscurve.sip.in
@@ -83,6 +83,8 @@ segments in a full circle)
 %Docstring
 Adds a curve to a painter path.
 %End
+    virtual QPainterPath asQPainterPath() const;
+
 
     virtual void drawAsPolygon( QPainter &p ) const = 0;
 %Docstring

diff --git a/python/core/auto_generated/geometry/qgscurvepolygon.sip.in b/python/core/auto_generated/geometry/qgscurvepolygon.sip.in
@@ -192,6 +192,8 @@ direction.
 .. versionadded:: 3.6
 %End
 
+    virtual QPainterPath asQPainterPath() const;
+
     virtual void draw( QPainter &p ) const;
 
     virtual void transform( const QgsCoordinateTransform &ct, QgsCoordinateTransform::TransformDirection d = QgsCoordinateTransform::ForwardTransform, bool transformZ = false ) throw( QgsCsException );

diff --git a/python/core/auto_generated/geometry/qgsgeometrycollection.sip.in b/python/core/auto_generated/geometry/qgsgeometrycollection.sip.in
@@ -149,6 +149,8 @@ An IndexError will be raised if no geometry with the specified index exists.
 
     virtual void draw( QPainter &p ) const;
 
+    virtual QPainterPath asQPainterPath() const;
+
 
     virtual bool fromWkb( QgsConstWkbPtr &wkb );
 

diff --git a/python/core/auto_generated/geometry/qgspoint.sip.in b/python/core/auto_generated/geometry/qgspoint.sip.in
@@ -382,6 +382,8 @@ Example
 
     virtual void draw( QPainter &p ) const;
 
+    virtual QPainterPath asQPainterPath() const;
+
     virtual void transform( const QgsCoordinateTransform &ct, QgsCoordinateTransform::TransformDirection d = QgsCoordinateTransform::ForwardTransform, bool transformZ = false ) throw( QgsCsException );
 
     virtual void transform( const QTransform &t, double zTranslate = 0.0, double zScale = 1.0, double mTranslate = 0.0, double mScale = 1.0 );

diff --git a/src/core/geometry/qgsabstractgeometry.h b/src/core/geometry/qgsabstractgeometry.h
@@ -42,6 +42,7 @@ class QDomElement;
 class QgsGeometryPartIterator;
 class QgsGeometryConstPartIterator;
 class QgsConstWkbPtr;
+class QPainterPath;
 
 typedef QVector< QgsPoint > QgsPointSequence;
 #ifndef SIP_RUN
@@ -356,6 +357,16 @@ class CORE_EXPORT QgsAbstractGeometry
      */
     virtual void draw( QPainter &p ) const = 0;
 
+    /**
+     * Returns the geometry represented as a QPainterPath.
+     *
+     * \warning not all geometry subclasses can be represented by a QPainterPath, e.g.
+     * points and multipoint geometries will return an empty path.
+     *
+     * \since QGIS 3.16
+     */
+    virtual QPainterPath asQPainterPath() const = 0;
+
     /**
      * Returns the vertex number corresponding to a vertex \a id.
      *

diff --git a/src/core/geometry/qgscurve.cpp b/src/core/geometry/qgscurve.cpp
@@ -58,6 +58,13 @@ bool QgsCurve::isRing() const
   return ( isClosed() && numPoints() >= 4 );
 }
 
+QPainterPath QgsCurve::asQPainterPath() const
+{
+  QPainterPath p;
+  addToPainterPath( p );
+  return p;
+}
+
 QgsCoordinateSequence QgsCurve::coordinateSequence() const
 {
   QgsCoordinateSequence sequence;

diff --git a/src/core/geometry/qgscurve.h b/src/core/geometry/qgscurve.h
@@ -89,6 +89,7 @@ class CORE_EXPORT QgsCurve: public QgsAbstractGeometry
      * Adds a curve to a painter path.
      */
     virtual void addToPainterPath( QPainterPath &path ) const = 0;
+    QPainterPath asQPainterPath() const override;
 
     /**
      * Draws the curve as a polygon on the specified QPainter.

diff --git a/src/core/geometry/qgscurvepolygon.cpp b/src/core/geometry/qgscurvepolygon.cpp
@@ -768,6 +768,20 @@ void QgsCurvePolygon::forceRHR()
   mInteriorRings = validRings;
 }
 
+QPainterPath QgsCurvePolygon::asQPainterPath() const
+{
+  QPainterPath p;
+  if ( mExteriorRing )
+    mExteriorRing->addToPainterPath( p );
+
+  for ( const QgsCurve *ring : mInteriorRings )
+  {
+    p.addPath( ring->asQPainterPath() );
+  }
+
+  return p;
+}
+
 void QgsCurvePolygon::draw( QPainter &p ) const
 {
   if ( !mExteriorRing )

diff --git a/src/core/geometry/qgscurvepolygon.h b/src/core/geometry/qgscurvepolygon.h
@@ -212,6 +212,7 @@ class CORE_EXPORT QgsCurvePolygon: public QgsSurface
      */
     void forceRHR();
 
+    QPainterPath asQPainterPath() const override;
     void draw( QPainter &p ) const override;
     void transform( const QgsCoordinateTransform &ct, QgsCoordinateTransform::TransformDirection d = QgsCoordinateTransform::ForwardTransform, bool transformZ = false ) override SIP_THROW( QgsCsException );
     void transform( const QTransform &t, double zTranslate = 0.0, double zScale = 1.0, double mTranslate = 0.0, double mScale = 1.0 ) override;

diff --git a/src/core/geometry/qgsgeometrycollection.cpp b/src/core/geometry/qgsgeometrycollection.cpp
@@ -308,6 +308,18 @@ void QgsGeometryCollection::draw( QPainter &p ) const
   }
 }
 
+QPainterPath QgsGeometryCollection::asQPainterPath() const
+{
+  QPainterPath p;
+  for ( const QgsAbstractGeometry *geom : mGeometries )
+  {
+    QPainterPath partPath = geom->asQPainterPath();
+    if ( !partPath.isEmpty() )
+      p.addPath( partPath );
+  }
+  return p;
+}
+
 bool QgsGeometryCollection::fromWkb( QgsConstWkbPtr &wkbPtr )
 {
   if ( !wkbPtr )

diff --git a/src/core/geometry/qgsgeometrycollection.h b/src/core/geometry/qgsgeometrycollection.h
@@ -176,6 +176,7 @@ class CORE_EXPORT QgsGeometryCollection: public QgsAbstractGeometry
     void transform( const QTransform &t, double zTranslate = 0.0, double zScale = 1.0, double mTranslate = 0.0, double mScale = 1.0 ) override;
 
     void draw( QPainter &p ) const override;
+    QPainterPath asQPainterPath() const override;
 
     bool fromWkb( QgsConstWkbPtr &wkb ) override;
     bool fromWkt( const QString &wkt ) override;

diff --git a/src/core/geometry/qgspoint.cpp b/src/core/geometry/qgspoint.cpp
@@ -321,6 +321,11 @@ void QgsPoint::draw( QPainter &p ) const
   p.drawRect( QRectF( mX - 2, mY - 2, 4, 4 ) );
 }
 
+QPainterPath QgsPoint::asQPainterPath() const
+{
+  return QPainterPath();
+}
+
 void QgsPoint::clear()
 {
   mX = mY = std::numeric_limits<double>::quiet_NaN();

diff --git a/src/core/geometry/qgspoint.h b/src/core/geometry/qgspoint.h
@@ -498,6 +498,7 @@ class CORE_EXPORT QgsPoint: public QgsAbstractGeometry
     json asJsonObject( int precision = 17 ) const override SIP_SKIP;
     QString asKml( int precision = 17 ) const override;
     void draw( QPainter &p ) const override;
+    QPainterPath asQPainterPath() const override;
     void transform( const QgsCoordinateTransform &ct, QgsCoordinateTransform::TransformDirection d = QgsCoordinateTransform::ForwardTransform, bool transformZ = false ) override SIP_THROW( QgsCsException );
     void transform( const QTransform &t, double zTranslate = 0.0, double zScale = 1.0, double mTranslate = 0.0, double mScale = 1.0 ) override;
     QgsCoordinateSequence coordinateSequence() const override;

diff --git a/tests/src/python/test_qgsgeometry.py b/tests/src/python/test_qgsgeometry.py
@@ -39,8 +39,8 @@
     QgsCoordinateReferenceSystem,
     QgsProject
 )
-from qgis.PyQt.QtCore import QDir, QPointF
-from qgis.PyQt.QtGui import QImage, QPainter, QPen, QColor, QBrush, QPainterPath, QPolygonF
+from qgis.PyQt.QtCore import QDir, QPointF, QRectF
+from qgis.PyQt.QtGui import QImage, QPainter, QPen, QColor, QBrush, QPainterPath, QPolygonF, QTransform
 
 from qgis.testing import (
     start_app,
@@ -5902,13 +5902,161 @@ def testGeometryDraw(self):
                 rendered_image = self.renderGeometry(geom, False, True)
                 assert self.imageCheck(test['name'] + '_aspolygon', test['as_polygon_reference_image'], rendered_image)
 
-    def imageCheck(self, name, reference_image, image):
+
+    def testGeometryAsQPainterPath(self):
+        '''Tests conversion of different geometries to QPainterPath, including bad/odd geometries.'''
+
+        empty_multipolygon = QgsMultiPolygon()
+        empty_multipolygon.addGeometry(QgsPolygon())
+        empty_polygon = QgsPolygon()
+        empty_linestring = QgsLineString()
+
+        tests = [{'name': 'LineString',
+                  'wkt': 'LineString (0 0,3 4,4 3)',
+                  'reference_image': 'linestring'},
+                 {'name': 'Empty LineString',
+                  'geom': QgsGeometry(empty_linestring),
+                  'reference_image': 'empty'},
+                 {'name': 'MultiLineString',
+                  'wkt': 'MultiLineString ((0 0, 1 0, 1 1, 2 1, 2 0), (3 1, 5 1, 5 0, 6 0))',
+                  'reference_image': 'multilinestring'},
+                 {'name': 'Polygon',
+                  'wkt': 'Polygon ((0 0, 10 0, 10 10, 0 10, 0 0),(5 5, 7 5, 7 7 , 5 7, 5 5))',
+                  'reference_image': 'polygon'},
+                 {'name': 'Empty Polygon',
+                  'geom': QgsGeometry(empty_polygon),
+                  'reference_image': 'empty'},
+                 {'name': 'MultiPolygon',
+                  'wkt': 'MultiPolygon (((0 0, 1 0, 1 1, 2 1, 2 2, 0 2, 0 0)),((4 0, 5 0, 5 2, 3 2, 3 1, 4 1, 4 0)))',
+                  'reference_image': 'multipolygon'},
+                 {'name': 'Empty MultiPolygon',
+                  'geom': QgsGeometry(empty_multipolygon),
+                  'reference_image': 'empty'},
+                 {'name': 'CircularString',
+                  'wkt': 'CIRCULARSTRING(268 415,227 505,227 406)',
+                  'reference_image': 'circular_string'},
+                 {'name': 'CompoundCurve',
+                  'wkt': 'COMPOUNDCURVE((5 3, 5 13), CIRCULARSTRING(5 13, 7 15, 9 13), (9 13, 9 3), CIRCULARSTRING(9 3, 7 1, 5 3))',
+                  'reference_image': 'compound_curve'},
+                 {'name': 'CurvePolygon',
+                  'wkt': 'CURVEPOLYGON(CIRCULARSTRING(1 3, 3 5, 4 7, 7 3, 1 3))',
+                  'reference_image': 'curve_polygon'},
+                 {'name': 'MultiCurve',
+                  'wkt': 'MultiCurve((5 5,3 5,3 3,0 3),CIRCULARSTRING(0 0, 2 1,2 2))',
+                  'reference_image': 'multicurve'},
+                 {'name': 'CurvePolygon_no_arc',  # refs #14028
+                  'wkt': 'CURVEPOLYGON(LINESTRING(1 3, 3 5, 4 7, 7 3, 1 3))',
+                  'reference_image': 'curve_polygon_no_arc'},
+                 {'name': 'CurvePolygonInteriorRings',
+                  'wkt': 'CurvePolygon(CircularString (20 30, 50 30, 50 90, 10 50, 20 30),LineString(30 45, 55 45, 30 75, 30 45))',
+                  'reference_image': 'curvepolygon_circularstring_interiorrings'},
+                 {'name': 'CompoundCurve With Line',
+                  'wkt': 'CompoundCurve(CircularString (20 30, 50 30, 50 90),LineString(50 90, 10 90))',
+                  'reference_image': 'compoundcurve_with_line'},
+                 {'name': 'Collection LineString',
+                  'wkt': 'GeometryCollection( LineString (0 0,3 4,4 3) )',
+                  'reference_image': 'collection_linestring'},
+                 {'name': 'Collection MultiLineString',
+                  'wkt': 'GeometryCollection (LineString(0 0, 1 0, 1 1, 2 1, 2 0), LineString(3 1, 5 1, 5 0, 6 0))',
+                  'reference_image': 'collection_multilinestring'},
+                 {'name': 'Collection Polygon',
+                  'wkt': 'GeometryCollection(Polygon ((0 0, 10 0, 10 10, 0 10, 0 0),(5 5, 7 5, 7 7 , 5 7, 5 5)))',
+                  'reference_image': 'collection_polygon'},
+                 {'name': 'Collection MultiPolygon',
+                  'wkt': 'GeometryCollection( Polygon((0 0, 1 0, 1 1, 2 1, 2 2, 0 2, 0 0)),Polygon((4 0, 5 0, 5 2, 3 2, 3 1, 4 1, 4 0)))',
+                  'reference_image': 'collection_multipolygon'},
+                 {'name': 'Collection CircularString',
+                  'wkt': 'GeometryCollection(CIRCULARSTRING(268 415,227 505,227 406))',
+                  'reference_image': 'collection_circular_string'},
+                 {'name': 'Collection CompoundCurve',
+                  'wkt': 'GeometryCollection(COMPOUNDCURVE((5 3, 5 13), CIRCULARSTRING(5 13, 7 15, 9 13), (9 13, 9 3), CIRCULARSTRING(9 3, 7 1, 5 3)))',
+                  'reference_image': 'collection_compound_curve'},
+                 {'name': 'Collection CurvePolygon',
+                  'wkt': 'GeometryCollection(CURVEPOLYGON(CIRCULARSTRING(1 3, 3 5, 4 7, 7 3, 1 3)))',
+                  'reference_image': 'collection_curve_polygon'},
+                 {'name': 'Collection CurvePolygon_no_arc',  # refs #14028
+                  'wkt': 'GeometryCollection(CURVEPOLYGON(LINESTRING(1 3, 3 5, 4 7, 7 3, 1 3)))',
+                  'reference_image': 'collection_curve_polygon_no_arc'},
+                 {'name': 'Collection Mixed',
+                  'wkt': 'GeometryCollection(Point(1 2), MultiPoint(3 3, 2 3), LineString (0 0,3 4,4 3), MultiLineString((3 1, 3 2, 4 2)), Polygon((0 0, 1 0, 1 1, 2 1, 2 2, 0 2, 0 0)), MultiPolygon(((4 0, 5 0, 5 1, 6 1, 6 2, 4 2, 4 0)),(( 1 4, 2 4, 1 5, 1 4))))',
+                  'reference_image': 'collection_mixed'},
+                 ]
+
+        for test in tests:
+
+            def get_geom():
+                if 'geom' not in test:
+                    geom = QgsGeometry.fromWkt(test['wkt'])
+                    assert geom and not geom.isNull(), 'Could not create geometry {}'.format(test['wkt'])
+                else:
+                    geom = test['geom']
+                return geom
+
+            geom = get_geom()
+            rendered_image = self.renderGeometryUsingPath(geom)
+            self.assertTrue(self.imageCheck(test['name'], test['reference_image'], rendered_image, control_path="geometry_path"), test['name'])
+
+            # Note - each test is repeated with the same geometry and reference image, but with added
+            # z and m dimensions. This tests that presence of the dimensions does not affect rendering
+
+            # test with Z
+            geom_z = get_geom()
+            geom_z.get().addZValue(5)
+            rendered_image = self.renderGeometryUsingPath(geom_z)
+            assert self.imageCheck(test['name'] + 'Z', test['reference_image'], rendered_image, control_path="geometry_path")
+
+            # test with ZM
+            geom_z.get().addMValue(15)
+            rendered_image = self.renderGeometryUsingPath(geom_z)
+            assert self.imageCheck(test['name'] + 'ZM', test['reference_image'], rendered_image, control_path="geometry_path")
+
+            # test with M
+            geom_m = get_geom()
+            geom_m.get().addMValue(15)
+            rendered_image = self.renderGeometryUsingPath(geom_m)
+            assert self.imageCheck(test['name'] + 'M', test['reference_image'], rendered_image, control_path="geometry_path")
+
+    def renderGeometryUsingPath(self, geom):
+        image = QImage(200, 200, QImage.Format_RGB32)
+        dest_bounds = image.rect()
+
+        geom = QgsGeometry(geom)
+
+        src_bounds = geom.buffer(geom.boundingBox().width() / 10, 5).boundingBox()
+        if src_bounds.width() and src_bounds.height():
+            scale = min(dest_bounds.width() / src_bounds.width(), dest_bounds.height() / src_bounds.height())
+            t = QTransform.fromScale(scale, -scale)
+            geom.transform(t)
+
+        src_bounds = geom.buffer(geom.boundingBox().width() / 10, 5).boundingBox()
+        t = QTransform.fromTranslate(-src_bounds.xMinimum(), -src_bounds.yMinimum())
+        geom.transform(t)
+
+        path = geom.constGet().asQPainterPath()
+
+        painter = QPainter()
+        painter.begin(image)
+        pen = QPen(QColor(0, 255, 255))
+        pen.setWidth(6)
+        painter.setPen(pen)
+        painter.setBrush(QBrush(QColor(255, 255, 0)))
+        try:
+            image.fill(QColor(0, 0, 0))
+
+            painter.drawPath(path)
+
+        finally:
+            painter.end()
+
+        return image
+
+    def imageCheck(self, name, reference_image, image, control_path="geometry"):
         self.report += "<h2>Render {}</h2>\n".format(name)
         temp_dir = QDir.tempPath() + '/'
         file_name = temp_dir + 'geometry_' + name + ".png"
         image.save(file_name, "PNG")
         checker = QgsRenderChecker()
-        checker.setControlPathPrefix("geometry")
+        checker.setControlPathPrefix(control_path)
         checker.setControlName("expected_" + reference_image)
         checker.setRenderedImage(file_name)
         checker.setColorTolerance(2)

diff --git a/...trol_images/geometry_path/expected_circular_string/expected_circular_string.png b/...trol_images/geometry_path/expected_circular_string/expected_circular_string.png
diff --git a/...ath/expected_collection_circular_string/expected_collection_circular_string.png b/...ath/expected_collection_circular_string/expected_collection_circular_string.png
diff --git a/..._path/expected_collection_compound_curve/expected_collection_compound_curve.png b/..._path/expected_collection_compound_curve/expected_collection_compound_curve.png
diff --git a/...ry_path/expected_collection_curve_polygon/expected_collection_curve_polygon.png b/...ry_path/expected_collection_curve_polygon/expected_collection_curve_polygon.png
diff --git a/...ed_collection_curve_polygon_no_arc/expected_collection_curve_polygon_no_arc.png b/...ed_collection_curve_polygon_no_arc/expected_collection_curve_polygon_no_arc.png
diff --git a/...ometry_path/expected_collection_fill_symbol/expected_collection_fill_symbol.png b/...ometry_path/expected_collection_fill_symbol/expected_collection_fill_symbol.png
diff --git a/...ometry_path/expected_collection_line_symbol/expected_collection_line_symbol.png b/...ometry_path/expected_collection_line_symbol/expected_collection_line_symbol.png
diff --git a/...geometry_path/expected_collection_linestring/expected_collection_linestring.png b/...geometry_path/expected_collection_linestring/expected_collection_linestring.png
diff --git a/...ry_path/expected_collection_marker_symbol/expected_collection_marker_symbol.png b/...ry_path/expected_collection_marker_symbol/expected_collection_marker_symbol.png
diff --git a/...ol_images/geometry_path/expected_collection_mixed/expected_collection_mixed.png b/...ol_images/geometry_path/expected_collection_mixed/expected_collection_mixed.png
diff --git a/...ath/expected_collection_multilinestring/expected_collection_multilinestring.png b/...ath/expected_collection_multilinestring/expected_collection_multilinestring.png
diff --git a/...etry_path/expected_collection_multipolygon/expected_collection_multipolygon.png b/...etry_path/expected_collection_multipolygon/expected_collection_multipolygon.png
diff --git a/...mages/geometry_path/expected_collection_polygon/expected_collection_polygon.png b/...mages/geometry_path/expected_collection_polygon/expected_collection_polygon.png
diff --git a/...ontrol_images/geometry_path/expected_compound_curve/expected_compound_curve.png b/...ontrol_images/geometry_path/expected_compound_curve/expected_compound_curve.png
diff --git a/...etry_path/expected_compoundcurve_with_line/expected_compoundcurve_with_line.png b/...etry_path/expected_compoundcurve_with_line/expected_compoundcurve_with_line.png
diff --git a/.../control_images/geometry_path/expected_curve_polygon/expected_curve_polygon.png b/.../control_images/geometry_path/expected_curve_polygon/expected_curve_polygon.png
diff --git a/...s/geometry_path/expected_curve_polygon_no_arc/expected_curve_polygon_no_arc.png b/...s/geometry_path/expected_curve_polygon_no_arc/expected_curve_polygon_no_arc.png
diff --git a/...ularstring_interiorrings/expected_curvepolygon_circularstring_interiorrings.png b/...ularstring_interiorrings/expected_curvepolygon_circularstring_interiorrings.png
diff --git a/tests/testdata/control_images/geometry_path/expected_empty/expected_empty.png b/tests/testdata/control_images/geometry_path/expected_empty/expected_empty.png
diff --git a/...stdata/control_images/geometry_path/expected_linestring/expected_linestring.png b/...stdata/control_images/geometry_path/expected_linestring/expected_linestring.png
diff --git a/...stdata/control_images/geometry_path/expected_multicurve/expected_multicurve.png b/...stdata/control_images/geometry_path/expected_multicurve/expected_multicurve.png
diff --git a/...trol_images/geometry_path/expected_multilinestring/expected_multilinestring.png b/...trol_images/geometry_path/expected_multilinestring/expected_multilinestring.png
diff --git a/...ta/control_images/geometry_path/expected_multipolygon/expected_multipolygon.png b/...ta/control_images/geometry_path/expected_multipolygon/expected_multipolygon.png
diff --git a/tests/testdata/control_images/geometry_path/expected_polygon/expected_polygon.png b/tests/testdata/control_images/geometry_path/expected_polygon/expected_polygon.png