Speed optimization for method VCommonSettings::GetCurveApproximationScale().

--HG--
branch : develop

src/libs/vmisc/vcommonsettings.cpp

@@ -95,6 +95,9 @@ const QString settingLabelUserDateFormats = QStringLiteral("label/userDateFormat
 const QString settingLabelTimeFormat      = QStringLiteral("label/timeFormat");
 const QString settingLabelUserTimeFormats = QStringLiteral("label/userTimeFormats");
 
+// Reading settings file is very expensive, cache curve approximation to speed up getting value
+qreal curveApproximationCached = -1;
+
 //---------------------------------------------------------------------------------------------------------------------
 QStringList ClearFormats(const QStringList &predefinedFormats, QStringList formats)
 {
@@ -1005,25 +1008,31 @@ void VCommonSettings::SetUserDefinedTimeFormats(const QStringList &formats)
 
 //---------------------------------------------------------------------------------------------------------------------
 qreal VCommonSettings::GetCurveApproximationScale() const
+{
+    if (curveApproximationCached < 0)
     {
         bool ok = false;
         const qreal scale = value(settingPatternCurveApproximationScale, defCurveApproximationScale).toDouble(&ok);
         if (ok && scale >= minCurveApproximationScale && scale <= maxCurveApproximationScale)
         {
-        return scale;
+            curveApproximationCached = scale;
         }
         else
         {
-        return defCurveApproximationScale;
+            curveApproximationCached = defCurveApproximationScale;
         }
     }
 
+    return curveApproximationCached;
+}
+
 //---------------------------------------------------------------------------------------------------------------------
 void VCommonSettings::SetCurveApproximationScale(qreal value)
 {
     if (value >= minCurveApproximationScale && value <= maxCurveApproximationScale)
     {
         setValue(settingPatternCurveApproximationScale, value);
+        curveApproximationCached = value;
     }
 }