Improve line/area measuring behaviour when the user has been informed that

they are probably using the wrong projection for the map canvas


git-svn-id: http://svn.osgeo.org/qgis/branches/Release-0_8_0@6396 c8812cc2-4d05-0410-92ff-de0c093fc19c

Author: g_j_m

src/gui/qgsmeasure.cpp

@@ -78,8 +78,7 @@ void QgsMeasure::activate()
   mRightMouseClicked = false;
 
   // ensure that we have correct settings
-  mCalc->setDefaultEllipsoid();
-  mCalc->setProjectAsSourceSRS();
+  updateProjection();
 
   // If we suspect that they have data that is projected, yet the
   // map SRS is set to a geographic one, warn them.
@@ -98,6 +97,7 @@ void QgsMeasure::activate()
            "system using the <tt>Settings:Project Properties</tt> menu."),
                          QMessageBox::Ok,
                          QMessageBox::NoButton);
+    mWrongProjectProjection = true;
   }
 }
 
@@ -125,6 +125,7 @@ QgsMeasure::~QgsMeasure()
 
 void QgsMeasure::restart(void )
 {
+    updateProjection();
     mPoints.resize(0);
     // Set one cell row where to update current distance
     // If measuring area, the table doesn't get shown
@@ -137,6 +138,7 @@ void QgsMeasure::restart(void )
     mRubberBand->reset(mMeasureArea);
 
     mRightMouseClicked = false;
+    mWrongProjectProjection = false;
 }
 
 void QgsMeasure::addPoint(QgsPoint &point)
@@ -145,6 +147,12 @@ void QgsMeasure::addPoint(QgsPoint &point)
     std::cout << "QgsMeasure::addPoint" << point.x() << ", " << point.y() << std::endl;
 #endif
 
+    if (mWrongProjectProjection)
+    {
+      updateProjection();
+      mWrongProjectProjection = false;
+    }
+
     // don't add points with the same coordinates
     if (mPoints.size() > 0 && point == mPoints[0])
       return;
@@ -325,6 +333,12 @@ void QgsMeasure::updateUi()
 
 }
 
+void QgsMeasure::updateProjection()
+{
+  mCalc->setDefaultEllipsoid();
+  mCalc->setProjectAsSourceSRS();
+}
+
 //////////////////////////
 
 void QgsMeasure::canvasPressEvent(QMouseEvent * e)

src/gui/qgsmeasure.h

@@ -105,6 +105,9 @@ public slots:
   //! shows/hides table, shows correct units
   void updateUi();
 
+  //! updates the projections we're using 
+  void updateProjection();
+
   QgsMapCanvas *mMapCanvas;
 
   //! distance/area calculator
@@ -125,6 +128,10 @@ public slots:
 
   //! indicates whether we've just done a right mouse click
   bool mRightMouseClicked;
+
+  //! indicates whether we've recently warned the user about having the wrong 
+  // project projection
+  bool mWrongProjectProjection;
 };
 
 #endif