Fixed int conversion error when enabling log scale

Author: PierreRaybaut

qwt/scale_engine.py

@@ -652,6 +652,7 @@ def autoScale(self, maxNumSteps, x1, x2, stepSize):
         logBase = self.base()
         interval = QwtInterval(x1/np.power(logBase, self.lowerMargin()),
                                x2*np.power(logBase, self.upperMargin()))
+        interval = interval.limited(LOG_MIN, LOG_MAX)
         if interval.maxValue()/interval.minValue() < logBase:
             linearScaler = QwtLinearScaleEngine()
             linearScaler.setAttributes(self.attributes())
@@ -887,4 +888,4 @@ def align(self, interval, stepSize):
 
         return qwtPowInterval(self.base(), QwtInterval(x1, x2))
 
-        
+