diff --git a/cmake/modules/FindQwt.cmake b/cmake/modules/FindQwt.cmake
index e52243f38..3ed74cff7 100644
--- a/cmake/modules/FindQwt.cmake
+++ b/cmake/modules/FindQwt.cmake
@@ -35,22 +35,25 @@
 
 SET(QWT_FOUND "NO")
 
+SET(HINT_INCLUDE_PATHS $ENV{QWT_DIR}/include
+                       $ENV{QWT_DIR}/src
+                       $ENV{QWTDIR}/include
+                       $ENV{QWTDIR}/src
+                       $ENV{QWT_ROOT}/include
+                       $ENV{QWT_ROOT}/src
+                       $ENV{QWTROOT}/include
+                       $ENV{QWTROOT}/src)
+SET(POTENTIAL_INCLUDE_PATHS /usr/local/qwt/include
+                            /usr/local/include
+                            /usr/include/qwt
+                            /usr/include/qwt-qt4
+                            /usr/include/qwt5
+                            /usr/include
+                            /opt/local/include/qwt) #macports path
+
 FIND_PATH(QWT_INCLUDE_DIR qwt.h
-  /usr/local/qwt/include
-  /usr/local/include
-  /usr/include/qwt
-  /usr/include/qwt-qt4
-  /usr/include/qwt5
-  /usr/include
-  /opt/local/include/qwt #macports path
-  $ENV{QWT_DIR}/include
-  $ENV{QWT_DIR}/src
-  $ENV{QWTDIR}/include
-  $ENV{QWTDIR}/src
-  $ENV{QWT_ROOT}/include
-  $ENV{QWT_ROOT}/src
-  $ENV{QWTROOT}/include
-  $ENV{QWTROOT}/src
+  HINTS ${HINT_INCLUDE_PATHS}
+  PATHS ${POTENTIAL_INCLUDE_PATHS}
 )
 
 SET(QWT_INCLUDE_DIRS ${QWT_INCLUDE_DIR})
@@ -82,12 +85,19 @@ IF( Qwt_FIND_VERSION AND QWT_VERSION_STRING )
   ENDIF()
 ENDIF()
 
-SET(POTENTIAL_LIBRARY_PATHS /usr/local/qwt/lib /usr/local/lib /usr/lib /opt/local/lib
-              $ENV{QWT_DIR}/lib $ENV{QWTDIR}/lib $ENV{QWT_ROOT}/lib $ENV{QWTROOT}/lib)
-              
 SET(QWT_NAMES ${QWT_NAMES} qwt qwt-qt4 qwt5 )
+SET(HINT_LIBRARY_PATHS $ENV{QWT_DIR}/lib
+                       $ENV{QWTDIR}/lib
+                       $ENV{QWT_ROOT}/lib
+                       $ENV{QWTROOT}/lib)
+SET(POTENTIAL_LIBRARY_PATHS /usr/local/qwt/lib
+                            /usr/local/lib
+                            /usr/lib
+                            /opt/local/lib)
+
 FIND_LIBRARY(QWT_LIBRARY
   NAMES ${QWT_NAMES}
+  HINTS ${HINT_LIBRARY_PATHS}
   PATHS ${POTENTIAL_LIBRARY_PATHS}
 )
 MARK_AS_ADVANCED(QWT_LIBRARY)
@@ -99,6 +109,7 @@ IF (QWT_LIBRARY)
     SET(QWT_NAMES_DEBUG qwtd qwtd-qt4 qwtd5 )
     FIND_LIBRARY(QWT_LIBRARY_DEBUG
       NAMES ${QWT_NAMES_DEBUG}
+      HINTS ${HINT_LIBRARY_PATHS}
       PATHS ${POTENTIAL_LIBRARY_PATHS}
     )
     MARK_AS_ADVANCED(QWT_LIBRARY_DEBUG)
diff --git a/graphics/lib/common/Lineplot.cpp b/graphics/lib/common/Lineplot.cpp
index 0f0c298ce..5fec806a9 100644
--- a/graphics/lib/common/Lineplot.cpp
+++ b/graphics/lib/common/Lineplot.cpp
@@ -94,7 +94,7 @@ Lineplot::Lineplot(QWidget *parent)
   axisScaleEngine(QwtPlot::yLeft)->setAttribute(QwtScaleEngine::Floating,true);
   axisScaleEngine(QwtPlot::yRight)->setAttribute(QwtScaleEngine::Floating,true);
 
-  zoomer_ = new MyZoomer(canvas());
+  zoomer_ = new MyZoomer(qobject_cast<QwtPlotCanvas*>(canvas()));
   zoomer_->setMousePattern(QwtEventPattern::MouseSelect1, Qt::LeftButton);
   zoomer_->setMousePattern(QwtEventPattern::MouseSelect2, Qt::LeftButton,
                            Qt::ControlModifier);
@@ -160,5 +160,9 @@ void Lineplot::resetZoom()
 
 void Lineplot::linkScales()
 {
+#if QWT_VERSION < 0x060100
   setAxisScaleDiv(QwtPlot::yRight, *axisScaleDiv(QwtPlot::yLeft));
+#else // QWT_VERSION < 0x060100
+  setAxisScaleDiv(QwtPlot::yRight, axisScaleDiv(QwtPlot::yLeft));
+#endif // QWT_VERSION < 0x060100
 }
diff --git a/graphics/lib/common/Pointplot.cpp b/graphics/lib/common/Pointplot.cpp
index b706851d1..aeb7b9098 100644
--- a/graphics/lib/common/Pointplot.cpp
+++ b/graphics/lib/common/Pointplot.cpp
@@ -83,7 +83,7 @@ Pointplot::Pointplot(QWidget *parent)
   memset(realPoints_, 0x0, numPoints_*sizeof(double));
   memset(imagPoints_, 0x0, numPoints_*sizeof(double));
 
-  zoomer_ = new MyZoomer(canvas());
+  zoomer_ = new MyZoomer(qobject_cast<QwtPlotCanvas*>(canvas()));
   zoomer_->setMousePattern(QwtEventPattern::MouseSelect1, Qt::LeftButton);
   zoomer_->setMousePattern(QwtEventPattern::MouseSelect2, Qt::LeftButton,
                            Qt::ControlModifier);
diff --git a/graphics/lib/common/Spectrogramplot.cpp b/graphics/lib/common/Spectrogramplot.cpp
index 6a6433dba..596f888e0 100644
--- a/graphics/lib/common/Spectrogramplot.cpp
+++ b/graphics/lib/common/Spectrogramplot.cpp
@@ -36,6 +36,7 @@
 #include <qprinter.h>
 #include <qprintdialog.h>
 #include <qwt_color_map.h>
+#include <qwt_plot_canvas.h>
 #include <qwt_plot_spectrogram.h>
 #include <qwt_scale_widget.h>
 #include <qwt_scale_draw.h>
@@ -116,7 +117,7 @@ Spectrogramplot::Spectrogramplot(int numDataPoints, int numRows, QWidget *parent
   // RightButton: zoom out by 1
   // Ctrl+RighButton: zoom out to full size
 
-  zoomer_ = new MyZoomer(canvas());
+  zoomer_ = new MyZoomer(qobject_cast<QwtPlotCanvas*>(canvas()));
   zoomer_->setMousePattern(QwtEventPattern::MouseSelect1,
       Qt::LeftButton);
   zoomer_->setMousePattern(QwtEventPattern::MouseSelect2,
diff --git a/graphics/lib/common/plot.cpp b/graphics/lib/common/plot.cpp
index 08e2faae3..0b2b82834 100644
--- a/graphics/lib/common/plot.cpp
+++ b/graphics/lib/common/plot.cpp
@@ -61,5 +61,6 @@ void plot_exit() {
 	if (plot_initiated) {
 		pthread_cancel(thread);
 	}
+  plot_initiated=0;
 }