Add some useful QgsVector methods

qgis · Apr 23, 2018 · 01f036c · 01f036c
1 parent d5647bc
commit 01f036c
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Showing 4 changed files with 47 additions and 0 deletions.
diff --git a/python/core/qgsvector.sip.in b/python/core/qgsvector.sip.in
@@ -52,6 +52,17 @@ Constructor for QgsVector taking x and y component values.
     double length() const;
 %Docstring
 Returns the length of the vector.
+
+.. seealso:: :py:func:`lengthSquared`
+%End
+
+    double lengthSquared() const;
+%Docstring
+Returns the length of the vector.
+
+.. versionadded:: 3.2
+
+.. seealso:: :py:func:`length`
 %End
 
     double x() const;
@@ -81,6 +92,14 @@ Returns the angle of the vector in radians.
     double angle( QgsVector v ) const;
 %Docstring
 Returns the angle between this vector and another vector in radians.
+%End
+
+    double crossProduct( QgsVector v ) const;
+%Docstring
+Returns the 2D cross product of this vector and another vector ``v``. (This is sometimes
+referred to as a "perpendicular dot product", and equals x1 * y1 - y1 * x2).
+
+.. versionadded:: 3.2
 %End
 
     QgsVector rotateBy( double rot ) const;

diff --git a/src/core/qgsvector.cpp b/src/core/qgsvector.cpp
@@ -99,6 +99,11 @@ double QgsVector::angle( QgsVector v ) const
   return v.angle() - angle();
 }
 
+double QgsVector::crossProduct( QgsVector v ) const
+{
+  return mX * v.y() - mY * v.x();
+}
+
 QgsVector QgsVector::rotateBy( double rot ) const
 {
   double angle = std::atan2( mY, mX ) + rot;

diff --git a/src/core/qgsvector.h b/src/core/qgsvector.h
@@ -89,9 +89,20 @@ class CORE_EXPORT QgsVector
 
     /**
      * Returns the length of the vector.
+     * \see lengthSquared()
      */
     double length() const;
 
+    /**
+     * Returns the length of the vector.
+     * \since QGIS 3.2
+     * \see length()
+     */
+    double lengthSquared() const
+    {
+      return mX * mX + mY * mY;
+    }
+
     /**
      * Returns the vector's x-component.
      * \see y()
@@ -119,6 +130,14 @@ class CORE_EXPORT QgsVector
      */
     double angle( QgsVector v ) const;
 
+    /**
+     * Returns the 2D cross product of this vector and another vector \a v. (This is sometimes
+     * referred to as a "perpendicular dot product", and equals x1 * y1 - y1 * x2).
+     *
+     * \since QGIS 3.2
+     */
+    double crossProduct( QgsVector v ) const;
+
     /**
      * Rotates the vector by a specified angle.
      * \param rot angle in radians

diff --git a/tests/src/core/testqgspoint.cpp b/tests/src/core/testqgspoint.cpp
@@ -274,6 +274,7 @@ void TestQgsPointXY::vector()
   // length
   QCOMPARE( v1.length(), 0.0 );
   QGSCOMPARENEAR( v2.length(), std::sqrt( 5.0 ), 0.000000001 );
+  QCOMPARE( v2.lengthSquared(), 5.0 );
 
   // perpVector
   QCOMPARE( QgsVector( 2, 3 ).perpVector().x(), -3.0 );
@@ -320,6 +321,9 @@ void TestQgsPointXY::vector()
   v1 -= v2;
   QCOMPARE( v1.x(), 1.0 );
   QCOMPARE( v1.y(), 3.0 );
+
+  // 2d cross product
+  QCOMPARE( QgsVector( 1, 3 ).crossProduct( QgsVector( 6, 9 ) ), -9.0 );
 }
 
 void TestQgsPointXY::asVariant()