Allow 0 (infinite) for scale dependent visibility

Fix #15414

src/app/qgsvectorlayerproperties.cpp

@@ -486,8 +486,8 @@ void QgsVectorLayerProperties::apply()
   // set up the scale based layer visibility stuff....
   mLayer->setScaleBasedVisibility( mScaleVisibilityGroupBox->isChecked() );
   // caution: layer uses scale denoms, widget uses true scales
-  mLayer->setMaximumScale( 1.0 / mScaleRangeWidget->minimumScale() );
-  mLayer->setMinimumScale( 1.0 / mScaleRangeWidget->maximumScale() );
+  mLayer->setMaximumScale( mScaleRangeWidget->maximumScaleDenom() );
+  mLayer->setMinimumScale( mScaleRangeWidget->minimumScaleDenom() );
 
   // provider-specific options
   if ( mLayer->dataProvider() )

src/gui/qgsscalecombobox.cpp

@@ -130,7 +130,7 @@ bool QgsScaleComboBox::setScaleString( const QString& scaleTxt )
   bool ok;
   double newScale = toDouble( scaleTxt, &ok );
   double oldScale = mScale;
-  if ( newScale < mMinScale )
+  if ( newScale < mMinScale && newScale != 0 )
   {
     newScale = mMinScale;
   }
@@ -246,7 +246,7 @@ double QgsScaleComboBox::toDouble( const QString& scaleString, bool * returnOk )
 void QgsScaleComboBox::setMinScale( double scale )
 {
   mMinScale = scale;
-  if ( mScale < scale )
+  if ( mScale < scale && mScale != 0 )
   {
     setScale( scale );
   }

src/gui/qgsscalecombobox.h

@@ -55,7 +55,13 @@ class GUI_EXPORT QgsScaleComboBox : public QComboBox
 
   public slots:
     void updateScales( const QStringList &scales = QStringList() );
-    //! Function to set the min scale
+
+    /**
+     * Set the minimum allowed scale.
+     * Anything scale lower than the minimum scale will automatically
+     * be converted to the minimum scale.
+     * Except for 0 which is always allowed.
+     */
     void setMinScale( double scale );
 
   protected:

src/gui/qgsscalerangewidget.cpp

@@ -90,6 +90,8 @@ void QgsScaleRangeWidget::setMapCanvas( QgsMapCanvas *mapCanvas )
 
 void QgsScaleRangeWidget::setMinimumScale( double scale )
 {
+  if ( qIsInf( scale ) )
+    scale = 0;
   mMinimumScaleWidget->setScale( scale );
 }
 
@@ -100,6 +102,8 @@ double QgsScaleRangeWidget::minimumScale()
 
 void QgsScaleRangeWidget::setMaximumScale( double scale )
 {
+  if ( qIsInf( scale ) )
+    scale = 0;
   mMaximumScaleWidget->setScale( scale );
 }
 
@@ -110,12 +114,20 @@ double QgsScaleRangeWidget::maximumScale()
 
 double QgsScaleRangeWidget::minimumScaleDenom()
 {
-  return qRound( 1.0 / maximumScale() );
+  double scale = maximumScale();
+  if ( scale == 0 )
+    return 0;
+  else
+    return qRound( 1.0 / scale );
 }
 
 double QgsScaleRangeWidget::maximumScaleDenom()
 {
-  return qRound( 1.0 / minimumScale() );
+  double scale = minimumScale();
+  if ( scale == 0 )
+    return 0;
+  else
+    return qRound( 1.0 / scale );
 }
 
 void QgsScaleRangeWidget::setScaleRange( double min, double max )

src/gui/qgsscalerangewidget.h

@@ -46,18 +46,30 @@ class GUI_EXPORT QgsScaleRangeWidget : public QWidget
     //! return the maximum scale
     double maximumScale();
 
-    //! return the minimum scale denominator ( = 1 / maximum scale )
+    /**
+     * Returns the minimum scale denominator ( = 1 / maximum scale )
+     * In case of maximum scale = 0 it will also return 0
+     */
     double minimumScaleDenom();
 
-    //! return the maximum scale denominator ( = 1 / minimum scale )
+    /**
+     * Returns the maximum scale denominator ( = 1 / minimum scale )
+     * In case of minimum scale = 0 it will also return 0
+     */
     double maximumScaleDenom();
 
     //! call to reload the project scales and apply them to the 2 scales combo boxes
     void reloadProjectScales();
 
   public slots:
+    /**
+     * Set the minimum scale. Infinite will be handled equally to 0 internally.
+     */
     void setMinimumScale( double scale );
 
+    /**
+     * Set the maximum scale. Infinite will be handled equally to 0 internally.
+     */
     void setMaximumScale( double scale );
 
     void setScaleRange( double min, double max );

src/gui/qgsscalewidget.cpp

@@ -66,5 +66,7 @@ void QgsScaleWidget::setScaleFromCanvas()
   setScale( 1 / mCanvas->scale() );
 }
 
-
-
+void QgsScaleWidget::setScale( double scale )
+{
+  return mScaleComboBox->setScale( scale );
+}

src/gui/qgsscalewidget.h

@@ -55,7 +55,7 @@ class GUI_EXPORT QgsScaleWidget : public QWidget
     //! Function to read the selected scale as double
     double scale() const { return mScaleComboBox->scale();}
     //! Function to set the selected scale from double
-    void setScale( double scale ) { return mScaleComboBox->setScale( scale ); }
+    void setScale( double scale );
     //! Function to read the min scale
     double minScale() const { return mScaleComboBox->minScale(); }