Fix label map tool crashes and rotation point calc

Author: dakcarto

src/app/qgsmaptoollabel.cpp

@@ -131,14 +131,16 @@ QgsPalLayerSettings& QgsMapToolLabel::currentLabelSettings( bool* ok )
   QgsVectorLayer* vlayer = currentLayer();
   if ( vlayer )
   {
-    if ( vlayer == mCurrentLayer )
-      return mCurrentSettings;
-
-    mCurrentLayer = vlayer;
-    mCurrentSettings = QgsPalLayerSettings::fromLayer( vlayer );
+    if ( vlayer != mCurrentLayer )
+    {
+      mCurrentLayer = vlayer;
+      mCurrentSettings = QgsPalLayerSettings::fromLayer( vlayer );
+    }
 
     if ( ok )
+    {
       *ok = true;
+    }
 
     return mCurrentSettings;
   }
@@ -337,11 +339,11 @@ bool QgsMapToolLabel::rotationPoint( QgsPoint& pos, bool ignoreUpsideDown, bool
 
   if ( mCurrentLabelPos.upsideDown && !ignoreUpsideDown )
   {
-    pos = mCurrentLabelPos.cornerPoints.at( 2 );
+    pos = cornerPoints.at( 2 );
   }
   else
   {
-    pos = mCurrentLabelPos.cornerPoints.at( 0 );
+    pos = cornerPoints.at( 0 );
   }
 
   //alignment always center/center and rotation 0 for diagrams
@@ -366,23 +368,16 @@ bool QgsMapToolLabel::rotationPoint( QgsPoint& pos, bool ignoreUpsideDown, bool
 //  QFont labelFont = labelFontCurrentFeature();
   QFontMetricsF labelFontMetrics( mCurrentLabelPos.labelFont );
 
-  //label text?
-  QString labelText = currentLabelText();
-
-  bool labelSettingsOk;
-  QgsPalLayerSettings& labelSettings = currentLabelSettings( &labelSettingsOk );
-  if ( !labelSettingsOk )
-  {
-    return false;
-  }
-
-  double labelSizeX, labelSizeY;
-  QgsFeature f;
-  if ( !currentFeature( f ) )
-  {
-    return false;
-  }
-  labelSettings.calculateLabelSize( &labelFontMetrics, labelText, labelSizeX, labelSizeY, &f );
+  // NOTE: this assumes the label corner points comprise a rectangle and that the
+  //       CRS supports equidistant measurements to accurately determine hypotenuse
+  QgsPoint cp_0 = cornerPoints.at( 0 );
+  QgsPoint cp_1 = cornerPoints.at( 1 );
+  QgsPoint cp_3 = cornerPoints.at( 3 );
+  //  QgsDebugMsg( QString( "cp_0: x=%1, y=%2" ).arg( cp_0.x() ).arg( cp_0.y() ) );
+  //  QgsDebugMsg( QString( "cp_1: x=%1, y=%2" ).arg( cp_1.x() ).arg( cp_1.y() ) );
+  //  QgsDebugMsg( QString( "cp_3: x=%1, y=%2" ).arg( cp_3.x() ).arg( cp_3.y() ) );
+  double labelSizeX = qSqrt( cp_0.sqrDist( cp_1 ) );
+  double labelSizeY = qSqrt( cp_0.sqrDist( cp_3 ) );
 
   double xdiff = 0;
   double ydiff = 0;