Adjust the arrow points to fit inside the specified bounding

 box, as opposed to adjusting the bounding box for the arrow points (except
 when bounding box is too small)

src/core/composer/qgscomposerarrow.cpp

@@ -26,6 +26,8 @@ QgsComposerArrow::QgsComposerArrow( QgsComposition* c )
     : QgsComposerItem( c )
     , mStartPoint( 0, 0 )
     , mStopPoint( 0, 0 )
+    , mStartXIdx( 0 )
+    , mStartYIdx( 0 )
     , mMarkerMode( DefaultMarker )
     , mArrowColor( QColor( 0, 0, 0 ) )
 {
@@ -39,6 +41,8 @@ QgsComposerArrow::QgsComposerArrow( const QPointF& startPoint, const QPointF& st
     , mMarkerMode( DefaultMarker )
     , mArrowColor( QColor( 0, 0, 0 ) )
 {
+  mStartXIdx = mStopPoint.x() < mStartPoint.x();
+  mStartYIdx = mStopPoint.y() < mStartPoint.y();
   initGraphicsSettings();
   adaptItemSceneRect();
 }
@@ -97,18 +101,31 @@ void QgsComposerArrow::paint( QPainter* painter, const QStyleOptionGraphicsItem
 
 void QgsComposerArrow::setSceneRect( const QRectF& rectangle )
 {
-  //maintain the relative position of start and stop point in the rectangle
-  double startPointXPos = ( mStartPoint.x() - pos().x() ) / rect().width();
-  double startPointYPos = ( mStartPoint.y() - pos().y() ) / rect().height();
-  double stopPointXPos = ( mStopPoint.x() - pos().x() ) / rect().width();
-  double stopPointYPos = ( mStopPoint.y() - pos().y() ) / rect().height();
+  if ( rectangle.width() < 0 )
+  {
+    mStartXIdx = 1 - mStartXIdx;
+  }
+  if ( rectangle.height() < 0 )
+  {
+    mStartYIdx = 1 - mStartYIdx;
+  }
 
-  mStartPoint.setX( rectangle.left() + startPointXPos * rectangle.width() );
-  mStartPoint.setY( rectangle.top() + startPointYPos * rectangle.height() );
-  mStopPoint.setX( rectangle.left() + stopPointXPos * rectangle.width() );
-  mStopPoint.setY( rectangle.top() + stopPointYPos * rectangle.height() );
+  double margin = computeMarkerMargin();
 
-  adaptItemSceneRect();
+  // Ensure the rectangle is at least as large as needed to include the markers
+  QRectF rect = rectangle.unite( QRectF( rectangle.x(), rectangle.y(), 2. * margin, 2. * margin ) );
+
+  // Compute new start and stop positions
+  double x[2] = {rect.x(), rect.x() + rect.width()};
+  double y[2] = {rect.y(), rect.y() + rect.height()};
+
+  double xsign = x[mStartXIdx] < x[1 - mStartXIdx] ? 1.0 : -1.0;
+  double ysign = y[mStartYIdx] < y[1 - mStartYIdx] ? 1.0 : -1.0;
+
+  mStartPoint = QPointF( x[mStartXIdx] + xsign * margin, y[mStartYIdx] + ysign * margin );
+  mStopPoint = QPointF( x[1 - mStartXIdx] - xsign * margin, y[1 - mStartYIdx] - ysign * margin );
+
+  QgsComposerItem::setSceneRect( rect );
 }
 
 void QgsComposerArrow::drawHardcodedMarker( QPainter *p, MarkerType type )
@@ -258,30 +275,41 @@ void QgsComposerArrow::setArrowHeadWidth( double width )
   adaptItemSceneRect();
 }
 
-void QgsComposerArrow::adaptItemSceneRect()
+double QgsComposerArrow::computeMarkerMargin() const
 {
-  //rectangle containing start and end point
-  QRectF rect = QRectF( qMin( mStartPoint.x(), mStopPoint.x() ), qMin( mStartPoint.y(), mStopPoint.y() ),
-                        qAbs( mStopPoint.x() - mStartPoint.x() ), qAbs( mStopPoint.y() - mStartPoint.y() ) );
-  double enlarge = 0;
+  double margin = 0;
   if ( mMarkerMode == DefaultMarker )
   {
-    enlarge = mPen.widthF() / 2.0 + mArrowHeadWidth / 2.0;
+    margin = mPen.widthF() / 2.0 + mArrowHeadWidth / 2.0;
   }
   else if ( mMarkerMode == NoMarker )
   {
-    enlarge = mPen.widthF() / 2.0;
+    margin = mPen.widthF() / 2.0;
   }
   else if ( mMarkerMode == SVGMarker )
   {
     double maxArrowHeight = qMax( mStartArrowHeadHeight, mStopArrowHeadHeight );
-    enlarge = mPen.widthF() / 2 + qMax( mArrowHeadWidth / 2.0, maxArrowHeight / 2.0 );
+    margin = mPen.widthF() / 2 + qMax( mArrowHeadWidth / 2.0, maxArrowHeight / 2.0 );
   }
+  return margin;
+}
 
+void QgsComposerArrow::adaptItemSceneRect()
+{
+  //rectangle containing start and end point
+  QRectF rect = QRectF( qMin( mStartPoint.x(), mStopPoint.x() ), qMin( mStartPoint.y(), mStopPoint.y() ),
+                        qAbs( mStopPoint.x() - mStartPoint.x() ), qAbs( mStopPoint.y() - mStartPoint.y() ) );
+  double enlarge = computeMarkerMargin();
   rect.adjust( -enlarge, -enlarge, enlarge, enlarge );
   QgsComposerItem::setSceneRect( rect );
 }
 
+void QgsComposerArrow::setMarkerMode( MarkerMode mode )
+{
+  mMarkerMode = mode;
+  adaptItemSceneRect();
+}
+
 bool QgsComposerArrow::writeXML( QDomElement& elem, QDomDocument & doc ) const
 {
   QDomElement composerArrowElem = doc.createElement( "ComposerArrow" );
@@ -362,7 +390,12 @@ bool QgsComposerArrow::readXML( const QDomElement& itemElem, const QDomDocument&
     mStopPoint.setY( stopPointElem.attribute( "y", "0.0" ).toDouble() );
   }
 
+  mStartXIdx = mStopPoint.x() < mStartPoint.x();
+  mStartYIdx = mStopPoint.y() < mStartPoint.y();
+
   adaptItemSceneRect();
   emit itemChanged();
   return true;
 }
+
+

src/core/composer/qgscomposerarrow.h

@@ -63,7 +63,7 @@ class CORE_EXPORT QgsComposerArrow: public QgsComposerItem
     void setArrowColor( const QColor& c ) { mArrowColor = c; }
 
     MarkerMode markerMode() const { return mMarkerMode;}
-    void setMarkerMode( MarkerMode mode ) {mMarkerMode = mode;}
+    void setMarkerMode( MarkerMode mode );
 
     /** stores state in Dom element
     * @param elem is Dom element corresponding to 'Composer' tag
@@ -88,6 +88,12 @@ class CORE_EXPORT QgsComposerArrow: public QgsComposerItem
     QPointF mStartPoint;
     QPointF mStopPoint;
 
+    /**Considering the rectangle as spanning [x[0], x[1]] x [y[0], y[1]], these
+     * indices specify which index {0, 1} corresponds to the start point
+     * coordinate of the respective dimension*/
+    int mStartXIdx;
+    int mStartYIdx;
+
     QPen mPen;
     QBrush mBrush;
 
@@ -110,6 +116,8 @@ class CORE_EXPORT QgsComposerArrow: public QgsComposerItem
     /**Adapts the item scene rect to contain the start point, the stop point including the arrow marker and the outline.
         Needs to be called whenever the arrow width/height, the outline with or the endpoints are changed*/
     void adaptItemSceneRect();
+    /**Computes the margin around the line necessary to include the markers */
+    double computeMarkerMargin() const;
     /**Draws the default marker at the line end*/
     void drawHardcodedMarker( QPainter* p, MarkerType type );
     /**Draws a user-defined marker (must be an svg file)*/
@@ -119,3 +127,5 @@ class CORE_EXPORT QgsComposerArrow: public QgsComposerItem
 };
 
 #endif // QGSCOMPOSERARROW_H
+
+