Cache summed up area for curve geometry classes

Avoids recalculation when area is retrieved multiple times
qgis · Sep 28, 2022 · 1c05421 · 1c05421
1 parent 14324b5
commit 1c05421
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Showing 6 changed files with 40 additions and 7 deletions.
diff --git a/python/core/auto_generated/geometry/qgscurve.sip.in b/python/core/auto_generated/geometry/qgscurve.sip.in
@@ -323,6 +323,7 @@ Scrolls the curve vertices so that they start with the vertex at the given index
 
 
 
+
 };
 
 /************************************************************************

diff --git a/src/core/geometry/qgscircularstring.cpp b/src/core/geometry/qgscircularstring.cpp
@@ -1347,8 +1347,14 @@ bool QgsCircularString::pointAt( int node, QgsPoint &point, Qgis::VertexType &ty
 
 void QgsCircularString::sumUpArea( double &sum ) const
 {
-  int maxIndex = numPoints() - 2;
+  if ( mHasCachedSummedUpArea )
+  {
+    sum += mSummedUpArea;
+    return;
+  }
 
+  int maxIndex = numPoints() - 2;
+  mSummedUpArea = 0;
   for ( int i = 0; i < maxIndex; i += 2 )
   {
     QgsPoint p1( mX[i], mY[i] );
@@ -1359,11 +1365,11 @@ void QgsCircularString::sumUpArea( double &sum ) const
     if ( p1 == p3 )
     {
       double r2 = QgsGeometryUtils::sqrDistance2D( p1, p2 ) / 4.0;
-      sum += M_PI * r2;
+      mSummedUpArea += M_PI * r2;
       continue;
     }
 
-    sum += 0.5 * ( mX[i] * mY[i + 2] - mY[i] * mX[i + 2] );
+    mSummedUpArea += 0.5 * ( mX[i] * mY[i + 2] - mY[i] * mX[i + 2] );
 
     //calculate area between circle and chord, then sum / subtract from total area
     double midPointX = ( p1.x() + p3.x() ) / 2.0;
@@ -1397,13 +1403,16 @@ void QgsCircularString::sumUpArea( double &sum ) const
 
     if ( !circlePointLeftOfLine )
     {
-      sum += circleChordArea;
+      mSummedUpArea += circleChordArea;
     }
     else
     {
-      sum -= circleChordArea;
+      mSummedUpArea -= circleChordArea;
     }
   }
+
+  mHasCachedSummedUpArea = true;
+  sum += mSummedUpArea;
 }
 
 bool QgsCircularString::hasCurvedSegments() const

diff --git a/src/core/geometry/qgscompoundcurve.cpp b/src/core/geometry/qgscompoundcurve.cpp
@@ -1148,10 +1148,19 @@ std::tuple<std::unique_ptr<QgsCurve>, std::unique_ptr<QgsCurve> > QgsCompoundCur
 
 void QgsCompoundCurve::sumUpArea( double &sum ) const
 {
+  if ( mHasCachedSummedUpArea )
+  {
+    sum += mSummedUpArea;
+    return;
+  }
+
+  mSummedUpArea = 0;
   for ( const QgsCurve *curve : mCurves )
   {
-    curve->sumUpArea( sum );
+    curve->sumUpArea( mSummedUpArea );
   }
+  mHasCachedSummedUpArea = true;
+  sum += mSummedUpArea;
 }
 
 void QgsCompoundCurve::close()

diff --git a/src/core/geometry/qgscurve.cpp b/src/core/geometry/qgscurve.cpp
@@ -295,6 +295,7 @@ void QgsCurve::clearCache() const
   mBoundingBox = QgsRectangle();
   mHasCachedValidity = false;
   mValidityFailureReason.clear();
+  mHasCachedSummedUpArea = false;
   QgsAbstractGeometry::clearCache();
 }
 

diff --git a/src/core/geometry/qgscurve.h b/src/core/geometry/qgscurve.h
@@ -341,6 +341,9 @@ class CORE_EXPORT QgsCurve: public QgsAbstractGeometry SIP_ABSTRACT
      */
     mutable QgsRectangle mBoundingBox;
 
+    mutable bool mHasCachedSummedUpArea = false;
+    mutable double mSummedUpArea = 0;
+
   private:
 
     mutable bool mHasCachedValidity = false;

diff --git a/src/core/geometry/qgslinestring.cpp b/src/core/geometry/qgslinestring.cpp
@@ -1936,6 +1936,13 @@ QgsPoint QgsLineString::centroid() const
 
 void QgsLineString::sumUpArea( double &sum ) const
 {
+  if ( mHasCachedSummedUpArea )
+  {
+    sum += mSummedUpArea;
+    return;
+  }
+
+  mSummedUpArea = 0;
   const int maxIndex = mX.size();
   if ( maxIndex == 0 )
     return;
@@ -1946,10 +1953,13 @@ void QgsLineString::sumUpArea( double &sum ) const
   double prevY = *y++;
   for ( int i = 1; i < maxIndex; ++i )
   {
-    sum += 0.5 * ( prevX * ( *y ) - prevY * ( *x ) );
+    mSummedUpArea += 0.5 * ( prevX * ( *y ) - prevY * ( *x ) );
     prevX = *x++;
     prevY = *y++;
   }
+
+  mHasCachedSummedUpArea = true;
+  sum += mSummedUpArea;
 }
 
 void QgsLineString::importVerticesFromWkb( const QgsConstWkbPtr &wkb )