diff --git a/src/calibrator.hh b/src/calibrator.hh
index 150cc1f..a6f9504 100644
--- a/src/calibrator.hh
+++ b/src/calibrator.hh
@@ -193,7 +193,7 @@ protected:
     bool along_axis(int xy, int x0, int y0);
 
     /// Apply new calibration, implementation dependent
-    virtual bool finish_data(const XYinfo new_axys) =0;
+    virtual bool finish_data(const XYinfo &new_axys) =0;
 
     /// Check whether the given name is a sysfs device name
     bool is_sysfs_name(const char* name);
diff --git a/src/calibrator/Evdev.cpp b/src/calibrator/Evdev.cpp
index 9a56475..0889056 100644
--- a/src/calibrator/Evdev.cpp
+++ b/src/calibrator/Evdev.cpp
@@ -258,7 +258,7 @@ bool CalibratorEvdev::finish(int width, int height)
 }
 
 // Activate calibrated data and output it
-bool CalibratorEvdev::finish_data(const XYinfo new_axys)
+bool CalibratorEvdev::finish_data(const XYinfo &new_axys)
 {
     bool success = true;
 
@@ -336,7 +336,7 @@ bool CalibratorEvdev::set_invert_xy(const int invert_x, const int invert_y)
     arr_cmd[0] = invert_x;
     arr_cmd[1] = invert_y;
 
-    int ret = xinput_do_set_int_prop("Evdev Axis Inversion", display, 8, 2, arr_cmd);
+    bool ret = xinput_do_set_int_prop("Evdev Axis Inversion", display, 8, 2, arr_cmd);
 
     if (verbose) {
         if (ret == true)
@@ -359,7 +359,7 @@ bool CalibratorEvdev::set_calibration(const XYinfo new_axys)
     arr_cmd[2] = new_axys.y.min;
     arr_cmd[3] = new_axys.y.max;
 
-    int ret = xinput_do_set_int_prop("Evdev Axis Calibration", display, 32, 4, arr_cmd);
+    bool ret = xinput_do_set_int_prop("Evdev Axis Calibration", display, 32, 4, arr_cmd);
 
     if (verbose) {
         if (ret == true)
diff --git a/src/calibrator/Evdev.hpp b/src/calibrator/Evdev.hpp
index b243090..9efe7d6 100644
--- a/src/calibrator/Evdev.hpp
+++ b/src/calibrator/Evdev.hpp
@@ -64,7 +64,7 @@ class CalibratorEvdev: public Calibrator
 
     /// calculate and apply the calibration
     virtual bool finish(int width, int height);
-    virtual bool finish_data(const XYinfo new_axys);
+    virtual bool finish_data(const XYinfo &new_axys);
 
     bool set_swapxy(const int swap_xy);
     bool set_invert_xy(const int invert_x, const int invert_y);
diff --git a/src/calibrator/EvdevTester.cpp b/src/calibrator/EvdevTester.cpp
index 5022946..0197988 100644
--- a/src/calibrator/EvdevTester.cpp
+++ b/src/calibrator/EvdevTester.cpp
@@ -31,7 +31,7 @@ CalibratorEvdevTester::CalibratorEvdevTester(const char* const device_name0, con
     //printf("Starting test driver\n");
 }
 
-bool CalibratorEvdevTester::finish_data(const XYinfo axis)
+bool CalibratorEvdevTester::finish_data(const XYinfo &axis)
 {
     new_axis = axis;
 
diff --git a/src/calibrator/EvdevTester.hpp b/src/calibrator/EvdevTester.hpp
index e75f282..30bfae4 100644
--- a/src/calibrator/EvdevTester.hpp
+++ b/src/calibrator/EvdevTester.hpp
@@ -41,7 +41,7 @@ class CalibratorEvdevTester: public CalibratorTesterInterface, public Calibrator
         const int thr_misclick=0, const int thr_doubleclick=0,
         const OutputType output_type=OUTYPE_AUTO, const char* geometry=0);
 
-    virtual bool finish_data(const XYinfo new_axis);
+    virtual bool finish_data(const XYinfo &new_axis);
 
     // emulate the driver processing the coordinates in 'raw'
     virtual XYinfo emulate_driver(const XYinfo& raw, bool useNewAxis, const XYinfo& screen, const XYinfo& device);
diff --git a/src/calibrator/Tester.cpp b/src/calibrator/Tester.cpp
index 4b1d9cd..abd2376 100644
--- a/src/calibrator/Tester.cpp
+++ b/src/calibrator/Tester.cpp
@@ -30,7 +30,7 @@ CalibratorTester::CalibratorTester(const char* const device_name0, const XYinfo&
     //printf("Starting test driver\n");
 }
 
-bool CalibratorTester::finish_data(const XYinfo axis)
+bool CalibratorTester::finish_data(const XYinfo &axis)
 {
     new_axis = axis;
 
diff --git a/src/calibrator/Tester.hpp b/src/calibrator/Tester.hpp
index 2bcad34..4532cd6 100644
--- a/src/calibrator/Tester.hpp
+++ b/src/calibrator/Tester.hpp
@@ -40,7 +40,7 @@ class CalibratorTester: public CalibratorTesterInterface, public Calibrator
         const int thr_misclick=0, const int thr_doubleclick=0,
         const OutputType output_type=OUTYPE_AUTO, const char* geometry=0);
 
-    virtual bool finish_data(const XYinfo new_axis);
+    virtual bool finish_data(const XYinfo &new_axis);
 
     // emulate the driver processing the coordinates in 'raw'
     virtual XYinfo emulate_driver(const XYinfo& raw,
diff --git a/src/calibrator/Usbtouchscreen.cpp b/src/calibrator/Usbtouchscreen.cpp
index 713b815..9bbafe3 100644
--- a/src/calibrator/Usbtouchscreen.cpp
+++ b/src/calibrator/Usbtouchscreen.cpp
@@ -77,7 +77,7 @@ CalibratorUsbtouchscreen::~CalibratorUsbtouchscreen()
     write_bool_parameter (p_swap_xy, val_swap_xy);
 }
 
-bool CalibratorUsbtouchscreen::finish_data(const XYinfo new_axys)
+bool CalibratorUsbtouchscreen::finish_data(const XYinfo &new_axys)
 {
     if (output_type != OUTYPE_AUTO) {
         fprintf(stderr, "ERROR: Usbtouchscreen Calibrator does not support the supplied --output-type\n");
diff --git a/src/calibrator/Usbtouchscreen.hpp b/src/calibrator/Usbtouchscreen.hpp
index 287e5dd..1898bf1 100644
--- a/src/calibrator/Usbtouchscreen.hpp
+++ b/src/calibrator/Usbtouchscreen.hpp
@@ -38,7 +38,7 @@ class CalibratorUsbtouchscreen: public Calibrator
         const bool use_timeout=false, const char* output_filename = 0);
     virtual ~CalibratorUsbtouchscreen();
 
-    virtual bool finish_data(const XYinfo new_axys);
+    virtual bool finish_data(const XYinfo &new_axys);
 
 protected:
     // Globals for kernel parameters from startup.
diff --git a/src/calibrator/XorgPrint.cpp b/src/calibrator/XorgPrint.cpp
index 582fa78..9ae04e5 100644
--- a/src/calibrator/XorgPrint.cpp
+++ b/src/calibrator/XorgPrint.cpp
@@ -33,7 +33,7 @@ CalibratorXorgPrint::CalibratorXorgPrint(const char* const device_name0, const X
     printf("\tIf these values are estimated wrong, either supply it manually with the --precalib option, or run the 'get_precalib.sh' script to automatically get it (through HAL).\n");
 }
 
-bool CalibratorXorgPrint::finish_data(const XYinfo new_axys)
+bool CalibratorXorgPrint::finish_data(const XYinfo &new_axys)
 {
     bool success = true;
 
diff --git a/src/calibrator/XorgPrint.hpp b/src/calibrator/XorgPrint.hpp
index 0d7e4cf..1083e0d 100644
--- a/src/calibrator/XorgPrint.hpp
+++ b/src/calibrator/XorgPrint.hpp
@@ -37,7 +37,7 @@ class CalibratorXorgPrint: public Calibrator
         const OutputType output_type=OUTYPE_AUTO, const char* geometry=0,
         const bool use_timeout=false, const char* output_filename = 0);
 
-    virtual bool finish_data(const XYinfo new_axys);
+    virtual bool finish_data(const XYinfo &new_axys);
 
 protected:
     bool output_xorgconfd(const XYinfo new_axys);
diff --git a/src/gui/gtkmm.hpp b/src/gui/gtkmm.hpp
index 49e8878..ef83fad 100644
--- a/src/gui/gtkmm.hpp
+++ b/src/gui/gtkmm.hpp
@@ -36,7 +36,7 @@ class CalibrationArea : public Gtk::DrawingArea
 public:
     CalibrationArea(Calibrator* w);
 
-protected:
+private:
     // Data
     Calibrator* calibrator;
     double X[4], Y[4];
diff --git a/src/gui/x11.cpp b/src/gui/x11.cpp
index 3d75e3b..4deaec1 100644
--- a/src/gui/x11.cpp
+++ b/src/gui/x11.cpp
@@ -270,14 +270,12 @@ void GuiCalibratorX11::redraw()
     }
 }
 
-bool GuiCalibratorX11::on_expose_event()
+void GuiCalibratorX11::on_expose_event()
 {
     redraw();
-
-    return true;
 }
 
-bool GuiCalibratorX11::on_timer_signal()
+void GuiCalibratorX11::on_timer_signal()
 {
     // Update clock
     if(calibrator->get_use_timeout()) {
@@ -295,11 +293,9 @@ bool GuiCalibratorX11::on_timer_signal()
                     clock_radius-clock_line_width, clock_radius-clock_line_width,
                     90*64, ((double)time_elapsed/(double)max_time) * -360 * 64);
     }
-
-    return true;
 }
 
-bool GuiCalibratorX11::on_button_press_event(XEvent event)
+void GuiCalibratorX11::on_button_press_event(XEvent event)
 {
     // Clear window, maybe a bit overdone, but easiest for me atm.
     // (goal is to clear possible message and other clicks)
@@ -329,8 +325,6 @@ bool GuiCalibratorX11::on_button_press_event(XEvent event)
 
     // Force a redraw
     redraw();
-
-    return true;
 }
 
 void GuiCalibratorX11::draw_message(const char* msg)
diff --git a/src/gui/x11.hpp b/src/gui/x11.hpp
index 02c8a4a..25c7f5e 100644
--- a/src/gui/x11.hpp
+++ b/src/gui/x11.hpp
@@ -35,7 +35,7 @@ class GuiCalibratorX11
     static void make_instance(Calibrator* w);
     static void give_timer_signal();
 
-protected:
+private:
     GuiCalibratorX11(Calibrator* w);
     ~GuiCalibratorX11();
 
@@ -63,16 +63,15 @@ class GuiCalibratorX11
     unsigned long pixel[NUM_COLORS];
 
     // Signal handlers
-    bool on_timer_signal();
-    bool on_expose_event();
-    bool on_button_press_event(XEvent event);
+    void on_timer_signal();
+    void on_expose_event();
+    void on_button_press_event(XEvent event);
 
     // Helper functions
     void set_display_size(int width, int height);
     void redraw();
     void draw_message(const char* msg);
 
-private:
     static GuiCalibratorX11* instance;
 };
 
diff --git a/src/tester.cpp b/src/tester.cpp
index 532e27a..9cb014a 100644
--- a/src/tester.cpp
+++ b/src/tester.cpp
@@ -117,4 +117,6 @@ int main() {
 
         printf("\n");
     } // loop over calibrators
+
+    delete calib;
 }