Merge pull request #5475 from nyalldawson/snap_to_grid

[FEATURE][processing] Native c++ snap to grid algorithm

python/core/geometry/qgsabstractgeometry.sip

@@ -402,6 +402,28 @@ Returns the centroid of the geometry
  :rtype: QgsAbstractGeometry
 %End
 
+    virtual QgsAbstractGeometry *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const = 0 /Factory/;
+%Docstring
+ Makes a new geometry with all the points or vertices snapped to the closest point of the grid.
+ Ownership is transferred to the caller.
+
+ If the gridified geometry could not be calculated a None will be returned.
+ It may generate an invalid geometry (in some corner cases).
+ It can also be thought as rounding the edges and it may be useful for removing errors.
+ Example:
+ \code
+ geometry->snappedToGrid(1, 1);
+ \endcode
+ In this case we use a 2D grid of 1x1 to gridify.
+ In this case, it can be thought like rounding the x and y of all the points/vertices to full units (remove all decimals).
+ \param hSpacing Horizontal spacing of the grid (x axis). 0 to disable.
+ \param vSpacing Vertical spacing of the grid (y axis). 0 to disable.
+ \param dSpacing Depth spacing of the grid (z axis). 0 (default) to disable.
+ \param mSpacing Custom dimension spacing of the grid (m axis). 0 (default) to disable.
+.. versionadded:: 3.0
+ :rtype: QgsAbstractGeometry
+%End
+
     virtual double vertexAngle( QgsVertexId vertex ) const = 0;
 %Docstring
  Returns approximate angle at a vertex. This is usually the average angle between adjacent
@@ -492,6 +514,18 @@ Returns the centroid of the geometry
 
   protected:
 
+    virtual QgsAbstractGeometry *createEmptyWithSameType() const = 0 /Factory/;
+%Docstring
+ Creates a new geometry with the same class and same WKB type as the original and transfers ownership.
+ To create it, the geometry is default constructed and then the WKB is changed.
+.. seealso:: clone()
+.. versionadded:: 3.0
+.. note::
+
+   Not available in Python bindings
+ :rtype: QgsAbstractGeometry
+%End
+
     virtual bool hasChildGeometries() const;
 %Docstring
  Returns whether the geometry has any child geometries (false for point / curve, true otherwise)

python/core/geometry/qgscircularstring.sip

@@ -25,16 +25,24 @@ class QgsCircularString: QgsCurve
     QgsCircularString();
 
     virtual bool operator==( const QgsCurve &other ) const;
+
     virtual bool operator!=( const QgsCurve &other ) const;
 
+
     virtual QString geometryType() const;
+
     virtual int dimension() const;
+
     virtual QgsCircularString *clone() const /Factory/;
+
     virtual void clear();
 
+
     virtual bool fromWkb( QgsConstWkbPtr &wkb );
+
     virtual bool fromWkt( const QString &wkt );
 
+
     virtual QByteArray asWkb() const;
 
     virtual QString asWkt( int precision = 17 ) const;
@@ -66,10 +74,14 @@ class QgsCircularString: QgsCurve
 %End
 
     virtual double length() const;
+
     virtual QgsPoint startPoint() const;
+
     virtual QgsPoint endPoint() const;
 
+
     virtual QgsLineString *curveToLine( double tolerance = M_PI_2 / 90, SegmentationToleranceType toleranceType = MaximumAngle ) const /Factory/;
+
 %Docstring
  Returns a new line string geometry corresponding to a segmentized approximation
  of the curve.
@@ -81,6 +93,9 @@ class QgsCircularString: QgsCurve
  :rtype: QgsLineString
 %End
 
+    virtual QgsCircularString *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const /Factory/;
+
+
     virtual void draw( QPainter &p ) const;
 
      virtual void transform( const QgsCoordinateTransform &ct, QgsCoordinateTransform::TransformDirection d = QgsCoordinateTransform::ForwardTransform,
@@ -89,17 +104,15 @@ class QgsCircularString: QgsCurve
 
     virtual void addToPainterPath( QPainterPath &path ) const;
 
-
     virtual void drawAsPolygon( QPainter &p ) const;
 
-
     virtual bool insertVertex( QgsVertexId position, const QgsPoint &vertex );
+
     virtual bool moveVertex( QgsVertexId position, const QgsPoint &newPos );
+
     virtual bool deleteVertex( QgsVertexId position );
 
-    virtual double closestSegment( const QgsPoint &pt, QgsPoint &segmentPt /Out/,
-                                   QgsVertexId &vertexAfter /Out/,
-                                   bool *leftOf /Out/ = 0, double epsilon = 4 * DBL_EPSILON ) const;
+    virtual double closestSegment( const QgsPoint &pt, QgsPoint &segmentPt /Out/, QgsVertexId &vertexAfter /Out/, bool *leftOf /Out/ = 0, double epsilon = 4 * DBL_EPSILON ) const;
 
     virtual bool pointAt( int node, QgsPoint &point, QgsVertexId::VertexType &type ) const;
 
@@ -119,21 +132,28 @@ class QgsCircularString: QgsCurve
 
     virtual QgsCircularString *reversed() const  /Factory/;
 
+
     virtual bool addZValue( double zValue = 0 );
+
     virtual bool addMValue( double mValue = 0 );
 
+
     virtual bool dropZValue();
+
     virtual bool dropMValue();
 
+
     virtual double xAt( int index ) const;
 
     virtual double yAt( int index ) const;
 
 
   protected:
+    virtual QgsCircularString *createEmptyWithSameType() const /Factory/;
 
     virtual QgsRectangle calculateBoundingBox() const;
 
+
 };
 
 

python/core/geometry/qgscompoundcurve.sip

@@ -25,16 +25,24 @@ class QgsCompoundCurve: QgsCurve
     ~QgsCompoundCurve();
 
     virtual bool operator==( const QgsCurve &other ) const;
+
     virtual bool operator!=( const QgsCurve &other ) const;
 
+
     virtual QString geometryType() const;
+
     virtual int dimension() const;
+
     virtual QgsCompoundCurve *clone() const /Factory/;
+
     virtual void clear();
 
+
     virtual bool fromWkb( QgsConstWkbPtr &wkb );
+
     virtual bool fromWkt( const QString &wkt );
 
+
     virtual QByteArray asWkb() const;
 
     virtual QString asWkt( int precision = 17 ) const;
@@ -47,14 +55,20 @@ class QgsCompoundCurve: QgsCurve
 
 
     virtual double length() const;
+
     virtual QgsPoint startPoint() const;
+
     virtual QgsPoint endPoint() const;
+
     virtual void points( QgsPointSequence &pts /Out/ ) const;
+
     virtual int numPoints() const;
+
     virtual bool isEmpty() const;
 
 
     virtual QgsLineString *curveToLine( double tolerance = M_PI_2 / 90, SegmentationToleranceType toleranceType = MaximumAngle ) const /Factory/;
+
 %Docstring
  Returns a new line string geometry corresponding to a segmentized approximation
  of the curve.
@@ -63,6 +77,9 @@ class QgsCompoundCurve: QgsCurve
  :rtype: QgsLineString
 %End
 
+    virtual QgsCompoundCurve *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const /Factory/;
+
+
     int nCurves() const;
 %Docstring
  Returns the number of curves in the geometry.
@@ -101,18 +118,16 @@ class QgsCompoundCurve: QgsCurve
 
     virtual void drawAsPolygon( QPainter &p ) const;
 
-
     virtual bool insertVertex( QgsVertexId position, const QgsPoint &vertex );
+
     virtual bool moveVertex( QgsVertexId position, const QgsPoint &newPos );
+
     virtual bool deleteVertex( QgsVertexId position );
 
-    virtual double closestSegment( const QgsPoint &pt, QgsPoint &segmentPt /Out/,
-                                   QgsVertexId &vertexAfter /Out/, bool *leftOf /Out/ = 0,
-                                   double epsilon = 4 * DBL_EPSILON ) const;
+    virtual double closestSegment( const QgsPoint &pt, QgsPoint &segmentPt /Out/, QgsVertexId &vertexAfter /Out/, bool *leftOf /Out/ = 0, double epsilon = 4 * DBL_EPSILON ) const;
 
     virtual bool pointAt( int node, QgsPoint &point, QgsVertexId::VertexType &type ) const;
 
-
     virtual void sumUpArea( double &sum /Out/ ) const;
 
 
@@ -135,12 +150,17 @@ Appends first point if not already closed.
 
     virtual QgsCompoundCurve *reversed() const /Factory/;
 
+
     virtual bool addZValue( double zValue = 0 );
+
     virtual bool addMValue( double mValue = 0 );
 
+
     virtual bool dropZValue();
+
     virtual bool dropMValue();
 
+
     virtual double xAt( int index ) const;
 
     virtual double yAt( int index ) const;
@@ -150,6 +170,9 @@ Appends first point if not already closed.
 
     virtual QgsRectangle calculateBoundingBox() const;
 
+    virtual QgsCompoundCurve *createEmptyWithSameType() const /Factory/;
+
+
 };
 
 

python/core/geometry/qgscurve.sip

@@ -184,6 +184,7 @@ class QgsCurve: QgsAbstractGeometry
     virtual int childCount() const;
     virtual QgsPoint childPoint( int index ) const;
 
+
 };
 
 /************************************************************************

python/core/geometry/qgscurvepolygon.sip

@@ -65,6 +65,8 @@ class QgsCurvePolygon: QgsSurface
 
     virtual QgsAbstractGeometry *boundary() const /Factory/;
 
+    virtual QgsCurvePolygon *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const /Factory/;
+
 
     int numInteriorRings() const;
 %Docstring
@@ -196,9 +198,13 @@ Adds an interior ring to the geometry (takes ownership)
     virtual QgsCurvePolygon *toCurveType() const /Factory/;
 
   protected:
+    virtual QgsCurvePolygon *createEmptyWithSameType() const /Factory/;
+
     virtual int childCount() const;
+
     virtual QgsAbstractGeometry *childGeometry( int index ) const;
 
+
   protected:
 
 

python/core/geometry/qgsgeometry.sip

@@ -665,6 +665,21 @@ Returns true if WKB of the geometry is of WKBMulti* type
  :rtype: QgsGeometry
 %End
 
+    QgsGeometry snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const;
+%Docstring
+ Returns a new geometry with all points or vertices snapped to the closest point of the grid.
+
+ If the gridified geometry could not be calculated (or was totally collapsed) an empty geometry will be returned.
+ Note that snapping to grid may generate an invalid geometry in some corner cases.
+ It can also be thought as rounding the edges and it may be useful for removing errors.
+ \param hSpacing Horizontal spacing of the grid (x axis). 0 to disable.
+ \param vSpacing Vertical spacing of the grid (y axis). 0 to disable.
+ \param dSpacing Depth spacing of the grid (z axis). 0 (default) to disable.
+ \param mSpacing Custom dimension spacing of the grid (m axis). 0 (default) to disable.
+.. versionadded:: 3.0
+ :rtype: QgsGeometry
+%End
+
     bool intersects( const QgsRectangle &r ) const;
 %Docstring
 Tests for intersection with a rectangle (uses GEOS)

python/core/geometry/qgsgeometrycollection.sip

@@ -51,6 +51,7 @@ class QgsGeometryCollection: QgsAbstractGeometry
 
     virtual void clear();
 
+    virtual QgsGeometryCollection *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const /Factory/;
     virtual QgsAbstractGeometry *boundary() const /Factory/;
 
     virtual void adjacentVertices( QgsVertexId vertex, QgsVertexId &previousVertex /Out/, QgsVertexId &nextVertex /Out/ ) const;
@@ -173,9 +174,13 @@ Adds a geometry and takes ownership. Returns true in case of success.
 
 
   protected:
+    virtual QgsGeometryCollection *createEmptyWithSameType() const /Factory/;
+
     virtual int childCount() const;
+
     virtual QgsAbstractGeometry *childGeometry( int index ) const;
 
+
   protected:
 
     virtual bool wktOmitChildType() const;

python/core/geometry/qgslinestring.sip

@@ -177,6 +177,8 @@ Closes the line string by appending the first point to the end of the line, if i
 
     virtual bool isEmpty() const;
 
+    virtual QgsLineString *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const /Factory/;
+
 
     virtual bool fromWkb( QgsConstWkbPtr &wkb );
 
@@ -268,6 +270,7 @@ Closes the line string by appending the first point to the end of the line, if i
 
 
   protected:
+    virtual QgsLineString *createEmptyWithSameType() const /Factory/;
 
     virtual QgsRectangle calculateBoundingBox() const;
 

python/core/geometry/qgsmulticurve.sip

@@ -52,6 +52,11 @@ class QgsMultiCurve: QgsGeometryCollection
 
 
 
+  protected:
+
+    virtual QgsMultiCurve *createEmptyWithSameType() const /Factory/;
+
+
 };
 
 

python/core/geometry/qgsmultilinestring.sip

@@ -49,6 +49,7 @@ class QgsMultiLineString: QgsMultiCurve
 %End
 
   protected:
+    virtual QgsMultiLineString *createEmptyWithSameType() const /Factory/;
 
     virtual bool wktOmitChildType() const;
 

python/core/geometry/qgsmultipoint.sip

@@ -50,6 +50,7 @@ class QgsMultiPointV2: QgsGeometryCollection
 
 
   protected:
+    virtual QgsMultiPointV2 *createEmptyWithSameType() const /Factory/;
 
     virtual bool wktOmitChildType() const;
 

python/core/geometry/qgsmultipolygon.sip

@@ -51,6 +51,7 @@ class QgsMultiPolygonV2: QgsMultiSurface
 
 
   protected:
+    virtual QgsMultiPolygonV2 *createEmptyWithSameType() const /Factory/;
 
     virtual bool wktOmitChildType() const;
 

python/core/geometry/qgsmultisurface.sip

@@ -44,6 +44,10 @@ class QgsMultiSurface: QgsGeometryCollection
 
 
 
+  protected:
+    virtual QgsMultiSurface *createEmptyWithSameType() const /Factory/;
+
+
 };