[FEATURE] New class for triangle

Adds a new geometry class for Triangle geometries

Methods include orthocenter, bisectors, medians, medial, circumscribed (center,
radius), inscribed (center, radius)

Also adds make_triangle expression function for creating triangles

Author: lbartoletti

python/core/core.sip

@@ -370,5 +370,6 @@
 %Include geometry/qgspointv2.sip
 %Include geometry/qgspolygon.sip
 %Include geometry/qgssurface.sip
+%Include geometry/qgstriangle.sip
 %Include geometry/qgswkbtypes.sip
 %Include geometry/qgswkbptr.sip

python/core/geometry/qgsgeometryutils.sip

@@ -67,4 +67,10 @@ class QgsGeometryUtils
 
     static QgsPointV2 midpoint (const QgsPointV2& pt1, const QgsPointV2& pt2);
 
+    static double gradient( const QgsPointV2& pt1, const QgsPointV2& pt2 );
+
+    static void coefficients(const QgsPointV2 &pt1, const QgsPointV2 &pt2, double& a /Out/, double& b /Out/, double& c /Out/);
+
+    static QgsLineString perpendicularSegment( const QgsPointV2& p, const QgsPointV2& s1, const QgsPointV2& s2 );
+
 };

python/core/geometry/qgstriangle.sip

@@ -0,0 +1,63 @@
+class QgsTriangle : public QgsPolygonV2
+{
+%TypeHeaderCode
+#include <qgstriangle.h>
+%End
+
+  public:
+    QgsTriangle();
+    QgsTriangle( const QgsPointV2 &p1, const QgsPointV2 &p2, const QgsPointV2 &p3 );
+    explicit QgsTriangle( const QgsPoint &p1, const QgsPoint &p2, const QgsPoint &p3 );
+    explicit QgsTriangle( const QPointF p1, const QPointF p2, const QPointF p3 );
+
+    // inherited: bool operator==( const QgsTriangle& other ) const;
+    // inherited: bool operator!=( const QgsTriangle& other ) const;
+
+    virtual QString geometryType() const;
+    virtual QgsTriangle* clone() const /Factory/;
+    void clear();
+
+    virtual bool fromWkb( QgsConstWkbPtr& wkbPtr );
+    bool fromWkt( const QString &wkt );
+    // inherited: QString asWkt( int precision = 17 ) const;
+    // inherited: QDomElement asGML2( QDomDocument& doc, int precision = 17, const QString& ns = "gml" ) const;
+    // inherited: QDomElement asGML3( QDomDocument& doc, int precision = 17, const QString& ns = "gml" ) const;
+    // inherited: QString asJSON( int precision = 17 ) const;
+
+    QgsPolygonV2* surfaceToPolygon() const /Factory/;
+    QgsAbstractGeometry* toCurveType() const /Factory/;
+
+    //overridden to handle LineString25D rings
+    virtual void setExteriorRing( QgsCurve* ring /Transfer/ );
+    virtual QgsAbstractGeometry* boundary() const /Factory/;
+    // inherited: double pointDistanceToBoundary( double x, double y ) const;
+    QgsPointV2 vertexAt( int atVertex ) const;
+
+    void addInteriorRing( QgsCurve* ring /Transfer/ ); // NOTE: no interior ring for triangle.
+    bool deleteVertex( QgsVertexId position );
+    bool insertVertex( QgsVertexId position, const QgsPointV2 &vertex );
+    bool moveVertex( QgsVertexId vId, const QgsPointV2& newPos );
+
+    QVector<double> lengths() const;
+    QVector<double> angles() const;
+
+    bool isIsocele( double lengthTolerance = 0.0001 ) const;
+    bool isEquilateral( double lengthTolerance = 0.0001 ) const;
+    bool isRight( double angleTolerance = 0.0001 ) const;
+    bool isScalene( double lengthTolerance = 0.0001 ) const;
+
+    QVector<QgsLineString> altitudes( ) const;
+    QVector<QgsLineString> medians( ) const;
+    QVector<QgsLineString> bisectors( double lengthTolerance = 0.0001 ) const;
+
+    QgsTriangle medial( ) const;
+    QgsPointV2 orthocenter( double lengthTolerance = 0.0001 ) const;
+    QgsPointV2 circumscribedCenter( ) const;
+    double circumscribedRadius( ) const;
+    // TODO:
+    // QgsCircle circumscribedCircle ( ) const; // need QgsCircle (from CADDigitize.CADCircle)
+    QgsPointV2 inscribedCenter( ) const;
+    double inscribedRadius( ) const;
+    // TODO:
+    // QgsCircle inscribedCircle ( ) const; // need QgsCircle (from CADDigitize.CADCircle)
+};

src/core/CMakeLists.txt

@@ -383,6 +383,7 @@ SET(QGIS_CORE_SRCS
   geometry/qgsmultisurface.cpp
   geometry/qgspointv2.cpp
   geometry/qgspolygon.cpp
+  geometry/qgstriangle.cpp
   geometry/qgswkbptr.cpp
   geometry/qgswkbtypes.cpp
 
@@ -922,6 +923,7 @@ SET(QGIS_CORE_HDRS
   geometry/qgsmultisurface.h
   geometry/qgspointv2.h
   geometry/qgspolygon.h
+  geometry/qgstriangle.h
   geometry/qgssurface.h
   geometry/qgswkbptr.h
   geometry/qgswkbtypes.h

src/core/geometry/qgsgeometryutils.cpp

@@ -21,6 +21,7 @@ email                : marco.hugentobler at sourcepole dot com
 #include "qgslinestring.h"
 #include "qgswkbptr.h"
 
+#include <memory>
 #include <QStringList>
 #include <QVector>
 #include <QRegularExpression>
@@ -834,6 +835,79 @@ QgsPointV2 QgsGeometryUtils::midpoint( const QgsPointV2 &pt1, const QgsPointV2 &
   return QgsPointV2( pType, x, y, z, m );
 }
 
+double QgsGeometryUtils::gradient( const QgsPointV2 &pt1, const QgsPointV2 &pt2 )
+{
+  double delta_x = pt2.x() - pt1.x();
+  double delta_y = pt2.y() - pt1.y();
+  if ( qgsDoubleNear( delta_x, 0.0 ) )
+  {
+    return INFINITY;
+  }
+
+  return delta_y / delta_x;
+}
+
+void QgsGeometryUtils::coefficients( const QgsPointV2 &pt1, const QgsPointV2 &pt2, double &a, double &b, double &c )
+{
+  if ( qgsDoubleNear( pt1.x(), pt2.x() ) )
+  {
+    a = 1;
+    b = 0;
+    c = -pt1.x();
+  }
+  else if ( qgsDoubleNear( pt1.y(), pt2.y() ) )
+  {
+    a = 0;
+    b = 1;
+    c = -pt1.y();
+  }
+  else
+  {
+    a = pt1.y() - pt2.y();
+    b = pt2.x() - pt1.x();
+    c = pt1.x() * pt2.y() - pt1.y() * pt2.x();
+  }
+
+}
+
+QgsLineString QgsGeometryUtils::perpendicularSegment( const QgsPointV2 &p, const QgsPointV2 &s1, const QgsPointV2 &s2 )
+{
+  QgsLineString line;
+  QgsPointV2 p2;
+
+  if ( ( p == s1 ) || ( p == s2 ) )
+  {
+    return line;
+  }
+
+  double a, b, c;
+  coefficients( s1, s2, a, b, c );
+
+  if ( qgsDoubleNear( a, 0 ) )
+  {
+    p2 = QgsPointV2( p.x(), s1.y() );
+  }
+  else if ( qgsDoubleNear( b, 0 ) )
+  {
+    p2 = QgsPointV2( s1.x(), p.y() );
+  }
+  else
+  {
+    double y = ( -c - a * p.x() ) / b;
+    double m = gradient( s1, s2 );
+    double d2 = 1 + m * m;
+    double H = p.y() - y;
+    double dx = m * H / d2;
+    double dy = m * dx;
+    p2 = QgsPointV2( p.x() + dx, y + dy );
+  }
+
+  line.addVertex( p );
+  line.addVertex( p2 );
+
+  return line;
+}
+
 double QgsGeometryUtils::lineAngle( double x1, double y1, double x2, double y2 )
 {
   double at = atan2( y2 - y1, x2 - x1 );

src/core/geometry/qgsgeometryutils.h

@@ -291,6 +291,33 @@ class CORE_EXPORT QgsGeometryUtils
      */
     static QgsPointV2 midpoint( const QgsPointV2 &pt1, const QgsPointV2 &pt2 );
 
+    /** Return the gradient of a line defined by points \a pt1 and \a pt2.
+     * @param pt1 first point.
+     * @param pt2 second point.
+     * @return The gradient of this linear entity, or infinity if vertical
+     * @note added in QGIS 3.0
+     */
+    static double gradient( const QgsPointV2 &pt1, const QgsPointV2 &pt2 );
+
+    /** Return the coefficients (a, b, c for equation "ax + by + c = 0") of a line defined by points \a pt1 and \a pt2.
+     * @param pt1 first point.
+     * @param pt2 second point.
+     * @param a Output parameter, a coefficient of the equation.
+     * @param b Output parameter, b coefficient of the equation.
+     * @param c Output parameter, c coefficient of the equation.
+     * @note added in QGIS 3.0
+     */
+    static void coefficients( const QgsPointV2 &pt1, const QgsPointV2 &pt2, double &a, double &b, double &c );
+
+    /**
+     * @brief Create a perpendicular line segment from p to segment [s1, s2]
+     * @param p The point
+     * @param s1 The segment start point
+     * @param s2 The segment end point
+     * @return A line (segment) from p to perpendicular point on segment [s1, s2]
+     */
+    static QgsLineString perpendicularSegment( const QgsPointV2 &p, const QgsPointV2 &s1, const QgsPointV2 &s2 );
+
     //! @note not available in Python bindings
     enum ComponentType
     {

src/core/geometry/qgslinestring.h

@@ -210,6 +210,7 @@ class CORE_EXPORT QgsLineString: public QgsCurve
     void fromWkbPoints( QgsWkbTypes::Type type, const QgsConstWkbPtr &wkb );
 
     friend class QgsPolygonV2;
+    friend class QgsTriangle;
 
 };