Merge pull request #31 from PierreRaybaut/Avoid-Divisions-by-Zero

Avoid errors when resizing canvas close to its minimum size

Author: PierreRaybaut

qwt/scale_engine.py

@@ -561,6 +561,8 @@ def buildMajorTicks(self, interval, stepSize):
         :return: Calculated ticks
         """
         numTicks = min([round(interval.width()/stepSize)+1, 10000])
+        if np.isnan(numTicks):
+            numTicks = 0
         ticks = [interval.minValue()]
         for i in range(1, int(numTicks-1)):
             ticks += [interval.minValue()+i*stepSize]

qwt/scale_map.py

@@ -146,7 +146,10 @@ def invTransform_scalar(self, p):
         
             :py:meth:`transform_scalar()`
         """
-        s = self.__ts1 + ( p - self.__p1 ) / self.__cnv
+        if self.__cnv == 0:
+            s = self.__ts1  # avoid divide by zero
+        else:
+            s = self.__ts1 + ( p - self.__p1 ) / self.__cnv
         if self.__transform:
             s = self.__transform.invTransform(s)
         return s