Fix endpoint swap on negative marker line offset

Fixes #13811
Includes testcase

(cherry-picked from 824fd7b)

Author: nyalldawson

src/core/symbology-ng/qgssymbollayerv2utils.cpp

@@ -781,7 +781,11 @@ QList<QPolygonF> offsetLine( QPolygonF polyline, double dist, QGis::GeometryType
 
       if ( QGis::flatType( tempGeometry->wkbType() ) == QGis::WKBLineString )
       {
-        resultLine.append( makeOffsetGeometry( tempGeometry->asPolyline() ) );
+        QgsPolyline line = tempGeometry->asPolyline();
+        // Reverse the line if offset was negative, see
+        // http://hub.qgis.org/issues/13811
+        if ( dist < 0 ) std::reverse(line.begin(), line.end() );
+        resultLine.append( makeOffsetGeometry( line ) );
         delete tempGeometry;
         return resultLine;
       }

tests/src/core/CMakeLists.txt

@@ -142,6 +142,7 @@ ADD_QGIS_TEST(maprenderertest testqgsmaprenderer.cpp)
 ADD_QGIS_TEST(maprotationtest testqgsmaprotation.cpp)
 ADD_QGIS_TEST(mapsettingstest testqgsmapsettings.cpp)
 ADD_QGIS_TEST(maptopixeltest testqgsmaptopixel.cpp)
+ADD_QGIS_TEST(markerlinessymboltest testqgsmarkerlinesymbol.cpp)
 ADD_QGIS_TEST(networkcontentfetcher testqgsnetworkcontentfetcher.cpp )
 ADD_QGIS_TEST(ogcutilstest testqgsogcutils.cpp)
 ADD_QGIS_TEST(painteffectregistrytest testqgspainteffectregistry.cpp)

tests/src/core/testqgsmarkerlinesymbol.cpp

@@ -0,0 +1,154 @@
+/***************************************************************************
+     testqgsmarkerlinesymbol.cpp
+     --------------------------------------
+    Date                 : Nov 12  2015
+    Copyright            : (C) 2015 by Sandro Santilli
+    Email                : strk@keybit.net
+ ***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+#include <QtTest/QtTest>
+#include <QObject>
+#include <QString>
+#include <QStringList>
+#include <QApplication>
+#include <QFileInfo>
+#include <QDir>
+
+//qgis includes...
+#include "qgsrasterlayer.h"
+#include "qgsvectorlayer.h"
+#include "qgsmultibandcolorrenderer.h"
+#include "qgsmaplayerregistry.h"
+#include "qgsapplication.h"
+#include "qgsmaprenderer.h"
+#include "qgspallabeling.h"
+#include "qgsfontutils.h"
+
+//qgis unit test includes
+#include <qgsrenderchecker.h>
+
+/** \ingroup UnitTests
+ * This is a unit test for the Marker Line symbol
+ */
+class TestQgsMarkerLineSymbol : public QObject
+{
+    Q_OBJECT
+  public:
+    TestQgsMarkerLineSymbol()
+        : mLinesLayer( 0 )
+        , mMapSettings( 0 )
+    {
+      mTestDataDir = QString( TEST_DATA_DIR ) + '/';
+    }
+
+    ~TestQgsMarkerLineSymbol();
+
+  private slots:
+    void initTestCase();// will be called before the first testfunction is executed.
+    void cleanupTestCase();// will be called after the last testfunction was executed.
+    void init() {} // will be called before each testfunction is executed.
+    void cleanup() {} // will be called after every testfunction.
+
+    void lineOffset();
+
+  private:
+    bool render( const QString& theFileName );
+
+    QString mTestDataDir;
+    QgsVectorLayer* mLinesLayer;
+    QgsMapSettings *mMapSettings;
+    QString mReport;
+};
+
+//runs before all tests
+void TestQgsMarkerLineSymbol::initTestCase()
+{
+  // init QGIS's paths - true means that all path will be inited from prefix
+  QgsApplication::init();
+  QgsApplication::initQgis();
+
+  mMapSettings = new QgsMapSettings();
+
+  QList<QgsMapLayer *> mapLayers;
+
+  //create a line layer that will be used in all tests...
+  QString myLinesFileName = mTestDataDir + "lines_cardinals.shp";
+  QFileInfo myLinesFileInfo( myLinesFileName );
+  mLinesLayer = new QgsVectorLayer( myLinesFileInfo.filePath(),
+                                    myLinesFileInfo.completeBaseName(), "ogr" );
+  mapLayers << mLinesLayer;
+
+  // Register all layers with the registry
+  QgsMapLayerRegistry::instance()->addMapLayers( mapLayers );
+
+  // This is needed to correctly set rotation center,
+  // the actual size doesn't matter as QgsRenderChecker will
+  // re-set it to the size of the expected image
+  mMapSettings->setOutputSize( QSize( 256, 256 ) );
+
+  mReport += "<h1>Line Marker Symbol Tests</h1>\n";
+
+  QgsFontUtils::loadStandardTestFonts( QStringList() << "Bold" );
+}
+
+TestQgsMarkerLineSymbol::~TestQgsMarkerLineSymbol()
+{
+
+}
+
+//runs after all tests
+void TestQgsMarkerLineSymbol::cleanupTestCase()
+{
+  delete mMapSettings;
+  QgsApplication::exitQgis();
+
+  QString myReportFile = QDir::tempPath() + "/qgistest.html";
+  QFile myFile( myReportFile );
+  if ( myFile.open( QIODevice::WriteOnly | QIODevice::Append ) )
+  {
+    QTextStream myQTextStream( &myFile );
+    myQTextStream << mReport;
+    myFile.close();
+  }
+}
+
+void TestQgsMarkerLineSymbol::lineOffset()
+{
+  mMapSettings->setLayers( QStringList() << mLinesLayer->id() );
+
+  // Negative offset on marker line
+  // See http://hub.qgis.org/issues/13811
+
+  QString qml = mTestDataDir + "marker_line_offset.qml";
+  bool success = false;
+  mLinesLayer->loadNamedStyle( qml, success );
+
+  QVERIFY( success );
+  mMapSettings->setExtent( QgsRectangle(-140,-140,140,140) );
+  QVERIFY( render( "line_offset" ) );
+
+  // TODO: -0.0 offset, see 
+  // http://hub.qgis.org/issues/13811#note-1
+}
+
+bool TestQgsMarkerLineSymbol::render( const QString& theTestType )
+{
+  mReport += "<h2>" + theTestType + "</h2>\n";
+  mMapSettings->setOutputDpi( 96 );
+  QgsRenderChecker checker;
+  checker.setControlPathPrefix( "markerlinesymbol" );
+  checker.setControlName( "expected_" + theTestType );
+  checker.setMapSettings( *mMapSettings );
+  bool result = checker.runTest( theTestType );
+  mReport += "\n\n\n" + checker.report();
+  return result;
+}
+
+QTEST_MAIN( TestQgsMarkerLineSymbol )
+#include "testqgsmarkerlinesymbol.moc"