From 4374c6e475620b7a90effdf726db03c48438d22d Mon Sep 17 00:00:00 2001
From: Nyall Dawson <nyall.dawson@gmail.com>
Date: Fri, 29 Sep 2017 10:58:45 +1000
Subject: [PATCH] Fix incorrect draw stacking when drawing rubber bands with
 secondary lines enabled

---
 python/gui/qgsrubberband.sip |  2 +-
 src/gui/qgsrubberband.cpp    | 52 ++++++++++++++++++++++--------------
 src/gui/qgsrubberband.h      |  2 +-
 3 files changed, 34 insertions(+), 22 deletions(-)

diff --git a/python/gui/qgsrubberband.sip b/python/gui/qgsrubberband.sip
index 43e0cc33c26..aa498b13d55 100644
--- a/python/gui/qgsrubberband.sip
+++ b/python/gui/qgsrubberband.sip
@@ -275,7 +275,7 @@ for tracking the mouse while drawing polylines or polygons.
   \param p The QPainter object
 %End
 
-    void drawShape( QPainter *p, QVector<QPointF> &pts );
+    void drawShape( QPainter *p, const QVector<QPointF> &pts );
 %Docstring
  Draws shape of the rubber band.
   \param p The QPainter object
diff --git a/src/gui/qgsrubberband.cpp b/src/gui/qgsrubberband.cpp
index 3917d724737..43040b4cfb7 100644
--- a/src/gui/qgsrubberband.cpp
+++ b/src/gui/qgsrubberband.cpp
@@ -405,35 +405,47 @@ void QgsRubberBand::setToCanvasRectangle( QRect rect )
 
 void QgsRubberBand::paint( QPainter *p )
 {
-  if ( !mPoints.isEmpty() )
+  if ( mPoints.isEmpty() )
+    return;
+
+  QVector< QVector<QPointF> > shapes;
+  for ( const QList<QgsPointXY> &line : qgsAsConst( mPoints ) )
   {
-    Q_FOREACH ( const QList<QgsPointXY> &line, mPoints )
+    QVector<QPointF> pts;
+    for ( const QgsPointXY &pt : line )
     {
-      QVector<QPointF> pts;
-      Q_FOREACH ( const QgsPointXY &pt, line )
-      {
-        const QPointF cur = toCanvasCoordinates( QgsPointXY( pt.x() + mTranslationOffsetX, pt.y() + mTranslationOffsetY ) ) - pos();
-        if ( pts.empty() || std::abs( pts.back().x() - cur.x() ) > 1 ||  std::abs( pts.back().y() - cur.y() ) > 1 )
-          pts.append( cur );
-      }
-
-      if ( mSecondaryPen.color().isValid() )
-      {
-        mSecondaryPen.setWidth( mPen.width() + 2 );
-
-        p->setBrush( Qt::NoBrush );
-        p->setPen( mSecondaryPen );
-        drawShape( p, pts );
-      }
+      const QPointF cur = toCanvasCoordinates( QgsPointXY( pt.x() + mTranslationOffsetX, pt.y() + mTranslationOffsetY ) ) - pos();
+      if ( pts.empty() || std::abs( pts.back().x() - cur.x() ) > 1 ||  std::abs( pts.back().y() - cur.y() ) > 1 )
+        pts.append( cur );
+    }
+    shapes << pts;
+  }
 
+  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 );
-      drawShape( p, pts );
+    }
+
+    for ( const QVector<QPointF> &shape : qgsAsConst( shapes ) )
+    {
+      drawShape( p, shape );
     }
   }
 }
 
-void QgsRubberBand::drawShape( QPainter *p, QVector<QPointF> &pts )
+void QgsRubberBand::drawShape( QPainter *p, const QVector<QPointF> &pts )
 {
   switch ( mGeometryType )
   {
diff --git a/src/gui/qgsrubberband.h b/src/gui/qgsrubberband.h
index 555f28fb56a..383954e7921 100644
--- a/src/gui/qgsrubberband.h
+++ b/src/gui/qgsrubberband.h
@@ -310,7 +310,7 @@ class GUI_EXPORT QgsRubberBand: public QgsMapCanvasItem
      *  \param p The QPainter object
      *  \param pts A list of points used to draw the shape
      */
-    void drawShape( QPainter *p, QVector<QPointF> &pts );
+    void drawShape( QPainter *p, const QVector<QPointF> &pts );
 
     //! Recalculates needed rectangle
     void updateRect();