add helper to build a QgsRectangle from a WKT string

Gustry · nyalldawson · commit 098611c3f69f · 2017-10-12T06:32:02.000+10:00
diff --git a/python/core/geometry/qgsrectangle.sip b/python/core/geometry/qgsrectangle.sip
@@ -44,6 +44,14 @@ Copy constructor
 
     ~QgsRectangle();
 
+    static QgsRectangle fromWkt( const QString &wkt );
+%Docstring
+ Creates a new rectangle from a WKT string.
+ The WKT must contain only 5 vertices, representing a rectangle aligned with X and Y axes.
+.. versionadded:: 3.0
+ :rtype: QgsRectangle
+%End
+
     void set( const QgsPointXY &p1, const QgsPointXY &p2 );
 %Docstring
  Sets the rectangle from two QgsPoints. The rectangle is
diff --git a/src/core/geometry/qgsrectangle.cpp b/src/core/geometry/qgsrectangle.cpp
@@ -24,6 +24,7 @@
 #include <QTransform>
 #include <QRegExp>
 
+#include "qgsgeometry.h"
 #include "qgspointxy.h"
 #include "qgsrectangle.h"
 #include "qgslogger.h"
@@ -59,6 +60,24 @@ QgsRectangle::QgsRectangle( const QgsRectangle &r )
   mYmax = r.yMaximum();
 }
 
+QgsRectangle QgsRectangle::fromWkt( const QString &wkt )
+{
+  QgsGeometry geom = QgsGeometry::fromWkt( wkt );
+  if ( geom.isMultipart() )
+    return QgsRectangle();
+
+  QgsPolygon poly = geom.asPolygon();
+
+  if ( poly.size() != 1 )
+    return QgsRectangle();
+
+  QgsPolyline polyline = geom.asPolygon().at( 0 );
+  if ( polyline.size() == 5 && polyline.at( 0 ) == polyline.at( 4 ) && geom.isGeosValid() )
+    return QgsRectangle( polyline.at( 0 ).x(), polyline.at( 0 ).y(), polyline.at( 2 ).x(), polyline.at( 2 ).y() );
+  else
+    return QgsRectangle();
+}
+
 void QgsRectangle::set( const QgsPointXY &p1, const QgsPointXY &p2 )
 {
   mXmin = p1.x();
diff --git a/src/core/geometry/qgsrectangle.h b/src/core/geometry/qgsrectangle.h
@@ -53,6 +53,13 @@ class CORE_EXPORT QgsRectangle
     // see https://github.com/qgis/QGIS/pull/4720#issuecomment-308652392
     ~QgsRectangle() = default;
 
+    /**
+    * Creates a new rectangle from a WKT string.
+    * The WKT must contain only 5 vertices, representing a rectangle aligned with X and Y axes.
+    * \since QGIS 3.0
+    */
+    static QgsRectangle fromWkt( const QString &wkt );
+
     /**
      * Sets the rectangle from two QgsPoints. The rectangle is
      * normalised after construction.
diff --git a/tests/src/core/testqgsrectangle.cpp b/tests/src/core/testqgsrectangle.cpp
@@ -26,6 +26,7 @@ class TestQgsRectangle: public QObject
     Q_OBJECT
   private slots:
     void isEmpty();
+    void fromWkt();
     void manipulate();
     void regression6194();
     void operators();
@@ -56,6 +57,25 @@ void TestQgsRectangle::isEmpty()
   QVERIFY( r.isEmpty() );
 }
 
+void TestQgsRectangle::fromWkt()
+{
+  QgsRectangle rect = QgsRectangle::fromWkt( QStringLiteral( "POLYGON((0 0,1 0,1 1,0 1,0 0))" ) );
+  QVERIFY( ! rect.isEmpty() );
+  QCOMPARE( rect.xMinimum(), 0.0 );
+  QCOMPARE( rect.yMinimum(), 0.0 );
+  QCOMPARE( rect.xMaximum(), 1.0 );
+  QCOMPARE( rect.yMaximum(), 1.0 );
+
+  QVERIFY( rect == QgsRectangle::fromWkt( rect.asWktPolygon() ) );
+
+  QVERIFY( QgsRectangle::fromWkt( QStringLiteral( "LINESTRING (0 0,1 0,1 1,0 1,0 0)" ) ).isEmpty() );
+  QVERIFY( QgsRectangle::fromWkt( QStringLiteral( "MULTIPOLYGON(((0 0,3 0,3 3,0 3,0 0)),((1 1, 1 2, 2 2, 2 1)))" ) ).isEmpty() );
+  QVERIFY( QgsRectangle::fromWkt( QStringLiteral( "MULTIPOLYGON(((0 0,3 0,3 3,0 3,0 0), (10 10,13 10,13 13,10 13,10 10)))" ) ).isEmpty() );
+  QVERIFY( QgsRectangle::fromWkt( QStringLiteral( "POLYGON((0 0,1 0,1 1,0 1,0 1))" ) ).isEmpty() );
+  QVERIFY( QgsRectangle::fromWkt( QStringLiteral( "POLYGON((0 0,1 0,1 1,0 1,0 1))" ) ).isEmpty() );
+  QVERIFY( QgsRectangle::fromWkt( QStringLiteral( "POLYGON((0 0,1 0,1 1,0 1))" ) ).isEmpty() );
+}
+
 void TestQgsRectangle::manipulate()
 {
   // Set up two intersecting rectangles and normalize
