Added QwtScaleDraw.setFixedSize/fixedSize methods to set the new fixed size option

When drawing text labels, if fixed size option is enabled, the axes
width and height won't change when axis range is changing. On the
contrary, if this option is disabled (default behavior), axes are
drawn in order to optimize layout space and depends on text label
individual sizes.

This option is not implemented in Qwt C++ library: this may be used
either as an optimization (updating plot layout is faster when this
option is enabled) or as an appearance preference (with Qwt default
behavior, the size of axes may change when zooming and/or panning
plot canvas which in some cases may not be desired).

Author: PierreRaybaut

CHANGELOG.md

@@ -1,5 +1,16 @@
 # History of changes
 
+## Version 0.5.0
+
+Various optimizations
+Added QwtScaleDraw.setFixedSize/fixedSize methods to set the new fixed size option (see documentation)
+
+## Version 0.4.0
+
+Color bar: fixed axis ticks shaking when color bar is enabled
+Fixed QwtPainter.drawColorBar for horizontal color bars (typo)
+Restored compatibility with original Qwt signals (QwtPlot, ...)
+
 ## Version 0.3.0
 
 Renamed the project (python-qwt --> PythonQwt), for various reasons.

qwt/plot.py

@@ -774,6 +774,20 @@ def setAxisLabelRotation(self, axisId, rotation):
         if self.axisValid(axisId):
             self.axisWidget(axisId).setLabelRotation(rotation)
 
+    def setAxisFixedSize(self, axisId, state):
+        """
+        Set tick labels fixed size option
+  
+        :param int axisId: Axis index
+        :param bool state: On/off 
+        
+        .. seealso::
+        
+            :py:meth:`qwt.scale_draw.QwtScaleDraw.setFixedSize()`
+        """
+        if self.axisValid(axisId):
+            self.axisWidget(axisId).setFixedSize(state)
+            
     def setAxisMaxMinor(self, axisId, maxMinor):
         """
         Set the maximum number of minor scale intervals for a specified axis

qwt/scale_draw.py

@@ -439,7 +439,7 @@ def __init__(self):
         self.alignment = QwtScaleDraw.BottomScale
         self.labelAlignment = 0
         self.labelRotation = 0.
-        
+        self.fixedSize = False
         self.pos = QPointF()
 
 
@@ -483,6 +483,7 @@ def __init__(self):
         QwtAbstractScaleDraw.__init__(self)
         self.__data = QwtScaleDraw_PrivateData()
         self.setLength(100)
+        self._max_label_sizes = {}
 
     def alignment(self):
         """
@@ -1124,6 +1125,49 @@ def labelAlignment(self):
             :py:meth:`setLabelAlignment()`, :py:meth:`labelRotation()`
         """
         return self.__data.labelAlignment
+
+    def setFixedSize(self, state):    
+        """
+        Set fixed size option state
+
+        When drawing text labels, if fixed size option is enabled, the axes 
+        width and height won't change when axis range is changing. On the 
+        contrary, if this option is disabled (default behavior), axes are 
+        drawn in order to optimize layout space and depends on text label 
+        individual sizes.
+        
+        This option is not implemented in Qwt C++ library: this may be used 
+        either as an optimization (updating plot layout is faster when this 
+        option is enabled) or as an appearance preference (with Qwt default 
+        behavior, the size of axes may change when zooming and/or panning 
+        plot canvas which in some cases may not be desired).
+
+        :param bool state: On/off        
+
+        .. seealso::
+        
+            :py:meth:`fixedSize()`
+        """
+        self.__data.fixedSize = state
+    
+    def fixedSize(self):
+        """
+        :return: True if fixed size option is enabled for labels
+        
+        .. seealso::
+        
+            :py:meth:`setFixedSize()`
+        """
+        return self.__data.fixedSize
+
+    def _get_max_label_size(self, font):
+        fid = font.toString()
+        size = self._max_label_sizes.get(fid)
+        if size is None:
+            size = self.labelSize(font, -999999)
+            return self._max_label_sizes.setdefault(fid, size)
+        else:
+            return size
 
     def maxLabelWidth(self, font):
         """
@@ -1133,7 +1177,10 @@ def maxLabelWidth(self, font):
         ticks = self.scaleDiv().ticks(QwtScaleDiv.MajorTick)
         if not ticks:
             return 0
-        return np.ceil(max([self.labelSize(font, v).width()
+        if self.fixedSize():
+            return self._get_max_label_size(font).width()
+        else:
+            return np.ceil(max([self.labelSize(font, v).width()
                             for v in ticks if self.scaleDiv().contains(v)]))
 
     def maxLabelHeight(self, font):
@@ -1144,7 +1191,10 @@ def maxLabelHeight(self, font):
         ticks = self.scaleDiv().ticks(QwtScaleDiv.MajorTick)
         if not ticks:
             return 0
-        return np.ceil(max([self.labelSize(font, v).height()
+        if self.fixedSize():
+            return self._get_max_label_size(font).height()
+        else:
+            return np.ceil(max([self.labelSize(font, v).height()
                             for v in ticks if self.scaleDiv().contains(v)]))
 
     def updateMap(self):