Fix for ticket #71 (I hope)

Also resolves a long standing issue with the scale units not updating
after being changed until the next map redraw (but the fix involves a
map redraw).


git-svn-id: http://svn.osgeo.org/qgis/trunk/qgis@5280 c8812cc2-4d05-0410-92ff-de0c093fc19c

Author: g_j_m

src/gui/qgsmapcanvas.cpp

@@ -457,6 +457,18 @@ void QgsMapCanvas::mapUnitsChanged()
   // We assume that if the map units have changed, the changed value
   // will be accessible from QgsProject.
   setMapUnits(QgsProject::instance()->mapUnits());
+  // Since the map units have changed, force a recalculation of the scale.
+  mMapRender->updateScale();
+  // And then force a redraw of the scale number in the status bar
+  updateScale();
+  // And then redraw the map to force the scale bar to update
+  // itself. This is less than ideal as the entire map gets redrawn
+  // just to get the scale bar to redraw itself. If we ask the scale
+  // bar to redraw itself without redrawing the map, the existing
+  // scale bar is not removed, and we end up with two scale bars in
+  // the same location. This can perhaps be fixed when/if the scale
+  // bar is done as a transparent layer on top of the map canvas.
+  render();
 }
 
 void QgsMapCanvas::zoomToSelected()

src/gui/qgsmaprender.cpp

@@ -57,6 +57,10 @@ QgsRect QgsMapRender::extent()
   return mExtent;
 }
 
+void QgsMapRender::updateScale()
+{
+  mScale = mScaleCalculator->calculate(mExtent, mSize.width());
+}
 
 bool QgsMapRender::setExtent(const QgsRect& extent)
 {
@@ -163,7 +167,7 @@ void QgsMapRender::adjustExtentToSize()
   mExtent.setYmax(dymax);
 
   // update the scale
-  mScale = mScaleCalculator->calculate(mExtent, myWidth);
+  updateScale();
 
 #ifdef QGISDEBUG
   QgsLogger::debug("Scale (assuming meters as map units) = 1", mScale, 1, __FILE__, __FUNCTION__, __LINE__);

src/gui/qgsmaprender.h

@@ -62,6 +62,9 @@ class QgsMapRender : public QObject
     double scale() const { return mScale; }
     double mupp() const { return mMupp; }
 
+    //! Recalculate the map scale
+    void updateScale();
+
     QGis::units mapUnits() const { return mMapUnits; }
     void setMapUnits(QGis::units u);