#8725-R: minor changes

python/core/qgssimplifymethod.sip

@@ -29,6 +29,9 @@ class QgsSimplifyMethod
     /** Gets the tolerance of simplification */
     double tolerance() const;
 
+    /** Returns the optimal tolerance for Douglas-Peucker simplification algorithms */
+    double toleranceForDouglasPeuckerAlgorithms() const;
+
     /** Sets whether the simplification executes after fetch the geometries from provider, otherwise it executes, when supported, in provider before fetch the geometries */
     void setForceLocalOptimization( bool localOptimization );
     /** Gets whether the simplification executes after fetch the geometries from provider, otherwise it executes, when supported, in provider before fetch the geometries */

src/core/qgssimplifymethod.cpp

@@ -53,6 +53,12 @@ void QgsSimplifyMethod::setForceLocalOptimization( bool localOptimization )
 {
   mForceLocalOptimization = localOptimization;
 }
+    
+double QgsSimplifyMethod::toleranceForDouglasPeuckerAlgorithms() const
+{
+  //TODO: define more precise value, now, it is experimental but conservative
+  return mTolerance / 5.0;
+}
 
 QgsAbstractGeometrySimplifier* QgsSimplifyMethod::createGeometrySimplifier( const QgsSimplifyMethod& simplifyMethod )
 {

src/core/qgssimplifymethod.h

@@ -48,6 +48,9 @@ class CORE_EXPORT QgsSimplifyMethod
     //! Gets the tolerance of simplification
     inline double tolerance() const { return mTolerance; }
 
+    //! Returns the optimal tolerance for Douglas-Peucker simplification algorithms
+    double toleranceForDouglasPeuckerAlgorithms() const;
+
     //! Sets whether the simplification executes after fetch the geometries from provider, otherwise it executes, when supported, in provider before fetch the geometries
     void setForceLocalOptimization( bool localOptimization );
     //! Gets whether the simplification executes after fetch the geometries from provider, otherwise it executes, when supported, in provider before fetch the geometries

src/providers/postgres/qgspostgresfeatureiterator.cpp

@@ -309,7 +309,7 @@ bool QgsPostgresFeatureIterator::declareCursor( const QString& whereClause )
 
       double tolerance = simplifyMethod.methodType() == QgsSimplifyMethod::OptimizeForRendering 
                ?
-               simplifyMethod.tolerance() / 5.0f /* experimental */
+               simplifyMethod.toleranceForDouglasPeuckerAlgorithms()
                :
                simplifyMethod.tolerance();
 

src/ui/qgsoptionsbase.ui

@@ -1755,7 +1755,7 @@
                      <item row="2" column="1" colspan="4">
                       <widget class="QCheckBox" name="mSimplifyDrawingAtProvider">
                        <property name="text">
-                        <string>Runs on provider side, otherwise it will execute once obtained the geometry from data source</string>
+                        <string>Simplify on provider side if possible</string>
                        </property>
                       </widget>
                      </item>

src/ui/qgsvectorlayerpropertiesbase.ui

@@ -1014,7 +1014,7 @@
                   <item row="2" column="1" colspan="4">
                    <widget class="QCheckBox" name="mSimplifyDrawingAtProvider">
                     <property name="text">
-                     <string>Runs on provider side, otherwise it will execute once obtained the geometry from data source</string>
+                     <string>Simplify on provider side if possible</string>
                     </property>
                    </widget>
                   </item>