Optimization/QwtPlot: updating layout only when necessary (contentsRect changed,

plot title, footer, axes titles (or axes enable state), legend changed)

Author: Pierre Raybaut

qwt/qwt_plot.py

@@ -152,6 +152,8 @@ def __init__(self, *args):
         QwtPlotDict.__init__(self)
         QFrame.__init__(self, parent)
 
+        self.__layout_state = None
+        
         self.__data = QwtPlot_PrivateData()
         from qwt.qwt_plot_layout import QwtPlotLayout
         self.__data.layout = QwtPlotLayout()
@@ -573,8 +575,21 @@ def replot(self):
                 self.__data.canvas.update(self.__data.canvas.contentsRect())
 
         self.setAutoReplot(doAutoReplot)
+
+    def get_layout_state(self):
+        return (self.contentsRect(),
+                self.__data.titleLabel.text(), self.__data.footerLabel.text(),
+                [(self.axisEnabled(axisId), self.axisTitle(axisId).text())
+                 for axisId in range(self.axisCnt)],
+                self.__data.legend)
 
     def updateLayout(self):
+        state = self.get_layout_state()
+        if self.__layout_state is not None and\
+           state == self.__layout_state:
+            return
+        self.__layout_state = state
+
         self.__data.layout.activate(self, self.contentsRect())
 
         titleRect = self.__data.layout.titleRect().toRect()

qwt/qwt_plot_layout.py

@@ -318,8 +318,7 @@ def __init__(self):
         ch = max([scaleData[QwtPlot.yLeft].h,
                   scaleData[QwtPlot.yRight].h]) + top + 1 + bottom + 1
         h += max([ch, minCanvasSize.height()])
-        labels = [plot.titleLabel(), plot.footerLabel()]
-        for label in labels:
+        for label in [plot.titleLabel(), plot.footerLabel()]:
             if label and not label.text().isEmpty():
                 centerOnCanvas = not plot.axisEnabled(QwtPlot.yLeft)\
                                  and plot.axisEnabled(QwtPlot.yRight)