Add feature to suppress zooming when holding down the shift key.

This allows users to measure a duration without zooming.

Htmldocs/release_notes.html

@@ -19,6 +19,7 @@
       <li>[new] OSCAR checks automatically for new releases.</li>
       <li>[new] Privacy feature allows suppressing profile info in Statistics page and printed reports.</li>
       <li>[new] Add option to print reports in black and white (monochrome).</li>
+      <li>[new] Hold down the Shift key while selecting a range on a chart to measure the duration without zooming.</li>
       <li>[fix] Improve support for rare events in 50-series Philips Respironics devices.</li>
       <li>[fix] Improve warning on Daily page when settings are missing.</li>
       <li>[fix] No longer zoom charts to maximum when clicking on chart with popup menu present.</li>

oscar/Graphs/gGraph.cpp

@@ -927,6 +927,11 @@ void gGraph::mouseReleaseEvent(QMouseEvent *event)
         m_selecting_area = false;
         m_selection.setWidth(0);
 
+        // Shift-drag only measures a range and should not zoom in.
+        if ((event->modifiers() & Qt::ShiftModifier) != 0) {
+            return;
+        }
+
         if (m_graphview->horizTravel() > mouse_movement_threshold) {
             x -= left; //+m_marginleft;
             //y -= top; //+m_margintop;