Add utility function to detect sharp corners

qgis · Jul 24, 2020 · 0641f3f · 0641f3f
1 parent ca5901b
commit 0641f3f
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diff --git a/python/core/auto_generated/symbology/qgssymbollayerutils.sip.in b/python/core/auto_generated/symbology/qgssymbollayerutils.sip.in
@@ -734,6 +734,13 @@ from the end of the line.
 
 May return an empty linestring if the substring is zero length.
 
+.. versionadded:: 3.16
+%End
+
+    static bool isSharpCorner( QPointF p1, QPointF p2, QPointF p3 );
+%Docstring
+Returns ``True`` if the angle formed by the line ``p1`` - ``p2`` - ``p3`` forms a "sharp" corner.
+
 .. versionadded:: 3.16
 %End
 

diff --git a/src/core/symbology/qgssymbollayerutils.cpp b/src/core/symbology/qgssymbollayerutils.cpp
@@ -4156,6 +4156,15 @@ QPolygonF QgsSymbolLayerUtils::polylineSubstring( const QPolygonF &polyline, dou
   return substringPoints;
 }
 
+bool QgsSymbolLayerUtils::isSharpCorner( QPointF p1, QPointF p2, QPointF p3 )
+{
+  double vertexAngle = M_PI - ( std::atan2( p3.y() - p2.y(), p3.x() - p2.x() ) - std::atan2( p2.y() - p1.y(), p2.x() - p1.x() ) );
+  vertexAngle = QgsGeometryUtils::normalizedAngle( vertexAngle );
+
+  // extreme angles form more than 45 degree angle at a node
+  return vertexAngle < M_PI * 135.0 / 180.0 || vertexAngle > M_PI * 225.0 / 180.0;
+}
+
 QgsExpression *QgsSymbolLayerUtils::fieldOrExpressionToExpression( const QString &fieldOrExpression )
 {
   if ( fieldOrExpression.isEmpty() )

diff --git a/src/core/symbology/qgssymbollayerutils.h b/src/core/symbology/qgssymbollayerutils.h
@@ -662,6 +662,13 @@ class CORE_EXPORT QgsSymbolLayerUtils
      */
     static QPolygonF polylineSubstring( const QPolygonF &polyline, double startOffset, double endOffset );
 
+    /**
+     * Returns TRUE if the angle formed by the line \a p1 - \a p2 - \a p3 forms a "sharp" corner.
+     *
+     * \since QGIS 3.16
+     */
+    static bool isSharpCorner( QPointF p1, QPointF p2, QPointF p3 );
+
     /**
      * Returns a new valid expression instance for given field or expression string.
      * If the input is not a valid expression, it is assumed that it is a field name and gets properly quoted.