[api] Add option for setting a line symbol to use when rendering

a QgsRubberBand

python/gui/auto_generated/qgsrubberband.sip.in

@@ -68,6 +68,7 @@ Creates a new RubberBand.
 :param geometryType: Defines how the data should be drawn onto the screen.
                      :py:class:`QgsWkbTypes`.LineGeometry, :py:class:`QgsWkbTypes`.PolygonGeometry or :py:class:`QgsWkbTypes`.PointGeometry
 %End
+    ~QgsRubberBand();
 
     void setColor( const QColor &color );
 %Docstring
@@ -345,6 +346,36 @@ Returns the rubberband as a Geometry
     virtual void updatePosition();
 
 
+    QgsSymbol *symbol() const;
+%Docstring
+Returns the symbol used for rendering the rubberband, if set.
+
+.. seealso:: :py:func:`setSymbol`
+
+.. versionadded:: 3.20
+%End
+
+    void setSymbol( QgsSymbol *symbol /Transfer/ );
+%Docstring
+Sets the ``symbol`` used for rendering the rubberband.
+
+Ownership of ``symbol`` is transferred to the rubberband.
+
+.. warning::
+
+   Only line symbols are currently supported.
+
+.. note::
+
+   Setting a symbol for the rubberband overrides any other appearance setting,
+   such as the :py:func:`~QgsRubberBand.strokeColor` or :py:func:`~QgsRubberBand.width`.
+
+
+.. seealso:: :py:func:`setSymbol`
+
+.. versionadded:: 3.20
+%End
+
   protected:
 
     virtual void paint( QPainter *p );

src/gui/qgsrubberband.cpp

@@ -20,6 +20,9 @@
 #include "qgsvectorlayer.h"
 #include "qgsproject.h"
 #include "qgsrectangle.h"
+#include "qgssymbol.h"
+#include "qgsrendercontext.h"
+
 #include <QPainter>
 
 QgsRubberBand::QgsRubberBand( QgsMapCanvas *mapCanvas, QgsWkbTypes::GeometryType geometryType )
@@ -43,6 +46,8 @@ QgsRubberBand::QgsRubberBand()
 {
 }
 
+QgsRubberBand::~QgsRubberBand() = default;
+
 void QgsRubberBand::setColor( const QColor &color )
 {
   setStrokeColor( color );
@@ -455,26 +460,45 @@ void QgsRubberBand::paint( QPainter *p )
     shapes.append( rings );
   }
 
-  int iterations = mSecondaryPen.color().isValid() ? 2 : 1;
-  for ( int i = 0; i < iterations; ++i )
+  if ( QgsLineSymbol *lineSymbol = dynamic_cast< QgsLineSymbol * >( mSymbol.get() ) )
   {
-    if ( i == 0 && iterations > 1 )
-    {
-      // first iteration with multi-pen painting, so use secondary pen
-      mSecondaryPen.setWidth( mPen.width() + 2 );
-      p->setBrush( Qt::NoBrush );
-      p->setPen( mSecondaryPen );
-    }
-    else
-    {
-      // "top" layer, use primary pen/brush
-      p->setBrush( mBrush );
-      p->setPen( mPen );
-    }
+    QgsRenderContext context( QgsRenderContext::fromQPainter( p ) );
+    context.setFlag( QgsRenderContext::Antialiasing, true );
 
+    lineSymbol->startRender( context );
     for ( const QVector<QPolygonF> &shape : qgis::as_const( shapes ) )
     {
       drawShape( p, shape );
+      for ( const QPolygonF &ring : shape )
+      {
+        lineSymbol->renderPolyline( ring, nullptr, context );
+      }
+    }
+    lineSymbol->stopRender( context );
+  }
+  else
+  {
+    int iterations = mSecondaryPen.color().isValid() ? 2 : 1;
+    for ( int i = 0; i < iterations; ++i )
+    {
+      if ( i == 0 && iterations > 1 )
+      {
+        // first iteration with multi-pen painting, so use secondary pen
+        mSecondaryPen.setWidth( mPen.width() + 2 );
+        p->setBrush( Qt::NoBrush );
+        p->setPen( mSecondaryPen );
+      }
+      else
+      {
+        // "top" layer, use primary pen/brush
+        p->setBrush( mBrush );
+        p->setPen( mPen );
+      }
+
+      for ( const QVector<QPolygonF> &shape : qgis::as_const( shapes ) )
+      {
+        drawShape( p, shape );
+      }
     }
   }
 }
@@ -630,6 +654,16 @@ void QgsRubberBand::updateRect()
   setRect( rect );
 }
 
+QgsSymbol *QgsRubberBand::symbol() const
+{
+  return mSymbol.get();
+}
+
+void QgsRubberBand::setSymbol( QgsSymbol *symbol )
+{
+  mSymbol.reset( symbol );
+}
+
 void QgsRubberBand::updatePosition()
 {
   // re-compute rectangle

src/gui/qgsrubberband.h

@@ -30,6 +30,7 @@
 
 class QgsVectorLayer;
 class QPaintEvent;
+class QgsSymbol;
 
 #ifdef SIP_RUN
 % ModuleHeaderCode
@@ -132,6 +133,7 @@ class GUI_EXPORT QgsRubberBand : public QgsMapCanvasItem
      *         QgsWkbTypes::LineGeometry, QgsWkbTypes::PolygonGeometry or QgsWkbTypes::PointGeometry
      */
     QgsRubberBand( QgsMapCanvas *mapCanvas SIP_TRANSFERTHIS, QgsWkbTypes::GeometryType geometryType = QgsWkbTypes::LineGeometry );
+    ~QgsRubberBand() override;
 
     /**
      * Sets the color for the rubberband.
@@ -385,6 +387,29 @@ class GUI_EXPORT QgsRubberBand : public QgsMapCanvasItem
 
     void updatePosition() override;
 
+    /**
+     * Returns the symbol used for rendering the rubberband, if set.
+     *
+     * \see setSymbol()
+     * \since QGIS 3.20
+     */
+    QgsSymbol *symbol() const;
+
+    /**
+     * Sets the \a symbol used for rendering the rubberband.
+     *
+     * Ownership of \a symbol is transferred to the rubberband.
+     *
+     * \warning Only line symbols are currently supported.
+     *
+     * \note Setting a symbol for the rubberband overrides any other appearance setting,
+     * such as the strokeColor() or width().
+     *
+     * \see setSymbol()
+     * \since QGIS 3.20
+     */
+    void setSymbol( QgsSymbol *symbol SIP_TRANSFER );
+
   protected:
 
     /**
@@ -423,6 +448,8 @@ class GUI_EXPORT QgsRubberBand : public QgsMapCanvasItem
     std::unique_ptr<QSvgRenderer> mSvgRenderer;
     QPoint mSvgOffset;
 
+    std::unique_ptr< QgsSymbol > mSymbol;
+
     /**
      * Nested lists used for multitypes
      */

tests/src/gui/testqgsrubberband.cpp

@@ -25,6 +25,8 @@
 #include <qgsvectorlayer.h>
 #include <qgsrubberband.h>
 #include <qgslogger.h>
+#include "qgssymbol.h"
+#include "qgsrenderchecker.h"
 
 class TestQgsRubberband : public QObject
 {
@@ -42,12 +44,14 @@ class TestQgsRubberband : public QObject
     void testBoundingRect(); //test for #12392
     void testVisibility(); //test for 12486
     void testClose(); //test closing geometry
+    void testSymbolRender();
 
   private:
     QgsMapCanvas *mCanvas = nullptr;
     QgsVectorLayer *mPolygonLayer = nullptr;
     QString mTestDataDir;
     QgsRubberBand *mRubberband = nullptr;
+    QString mReport;
 };
 
 void TestQgsRubberband::initTestCase()
@@ -75,6 +79,7 @@ void TestQgsRubberband::initTestCase()
   mCanvas->hide();
 
   mRubberband = nullptr;
+  mReport += QLatin1String( "<h1>Rubberband Tests</h1>\n" );
 }
 
 void TestQgsRubberband::cleanupTestCase()
@@ -83,6 +88,15 @@ void TestQgsRubberband::cleanupTestCase()
   delete mPolygonLayer;
   delete mCanvas;
 
+  QString myReportFile = QDir::tempPath() + "/qgistest.html";
+  QFile myFile( myReportFile );
+  if ( myFile.open( QIODevice::WriteOnly | QIODevice::Append ) )
+  {
+    QTextStream myQTextStream( &myFile );
+    myQTextStream << mReport;
+    myFile.close();
+  }
+
   QgsApplication::exitQgis();
 }
 
@@ -216,6 +230,42 @@ void TestQgsRubberband::testClose()
   QCOMPARE( r.partSize( 0 ), 4 );
 }
 
+void TestQgsRubberband::testSymbolRender()
+{
+  std::unique_ptr< QgsMapCanvas > canvas = qgis::make_unique< QgsMapCanvas >();
+  canvas->setDestinationCrs( QgsCoordinateReferenceSystem( QStringLiteral( "EPSG:4326" ) ) );
+  canvas->setFrameStyle( 0 );
+  canvas->resize( 600, 400 );
+  canvas->setExtent( QgsRectangle( 10, 30, 20, 35 ) );
+  canvas->show();
+
+  QgsRubberBand r( canvas.get(), QgsWkbTypes::LineGeometry );
+  r.addGeometry( QgsGeometry::fromWkt( QStringLiteral( "LineString( 12 32, 18 33)" ) ) );
+
+  std::unique_ptr< QgsLineSymbol > lineSymbol( QgsLineSymbol::createSimple(
+  {
+    { QStringLiteral( "line_color" ), QStringLiteral( "#0000ff" ) },
+    { QStringLiteral( "line_width" ), QStringLiteral( "3" )},
+    { QStringLiteral( "capstyle" ), QStringLiteral( "round" )}
+  } ) );
+  r.setSymbol( lineSymbol.release() );
+
+  QPixmap pixmap( canvas->size() );
+  QPainter painter( &pixmap );
+  canvas->render( &painter );
+  painter.end();
+  QString destFile = QDir::tempPath() + QStringLiteral( "/rubberband_line_symbol.png" );
+  pixmap.save( destFile );
+
+  QgsRenderChecker checker;
+  checker.setControlPathPrefix( QStringLiteral( "rubberband" ) );
+  checker.setControlName( QStringLiteral( "expected_line_symbol" ) );
+  checker.setRenderedImage( destFile );
+  bool result = checker.compareImages( QStringLiteral( "expected_line_symbol" ) );
+  mReport += checker.report();
+  QVERIFY( result );
+}
+
 
 QGSTEST_MAIN( TestQgsRubberband )
 #include "testqgsrubberband.moc"