Add check to make sure minScale<=maxScale.

Those two fields are present in the vector layer properties. It
was possible to set a minScale bigger than the maxScale.
Now, the maxScale is forced to minScale if the user tries to
set it to a lower value.

python/gui/qgsscalecombobox.sip

@@ -17,9 +17,11 @@ class QgsScaleComboBox : QComboBox
     //! Function to set the selected scale from text
     bool setScaleString( const QString& scaleTxt );
     //! Function to read the selected scale as double
-    double scale();
+    double scale() const;
     //! Function to set the selected scale from double
     void setScale( double scale );
+    //! Function to read the min scale
+    double minScale() const;
 
     //! Helper function to convert a double to scale string
     // Performs rounding, so an exact representation is not to
@@ -30,10 +32,12 @@ class QgsScaleComboBox : QComboBox
 
   signals:
     //! Signal is emitted when *user* has finished editing/selecting a new scale.
-    void scaleChanged();
+    void scaleChanged( double scale );
 
   public slots:
     void updateScales( const QStringList &scales = QStringList() );
+    //! Function to set the min scale
+    void setMinScale( double scale );
 
   protected:
     void showPopup();

python/gui/qgsscalewidget.sip

@@ -26,9 +26,11 @@ class QgsScaleWidget : QWidget
     //! Function to set the selected scale from text
     bool setScaleString( const QString& scaleTxt );
     //! Function to read the selected scale as double
-    double scale();
+    double scale() const;
     //! Function to set the selected scale from double
     void setScale( double scale );
+    //! Function to read the min scale
+    double minScale() const;
 
     //! Helper function to convert a double to scale string
     // Performs rounding, so an exact representation is not to
@@ -43,9 +45,12 @@ class QgsScaleWidget : QWidget
     //! assign the current scale from the map canvas
     void setScaleFromCanvas();
 
+    //! Function to set the min scale
+    void setMinScale( double scale );
+
   signals:
     //! Signal is emitted when *user* has finished editing/selecting a new scale.
-    void scaleChanged();
+    void scaleChanged( double scale );
 
 
 };

src/app/qgisapp.cpp

@@ -2057,7 +2057,7 @@ void QgisApp::createStatusBar()
   mScaleEdit->setToolTip( tr( "Current map scale (formatted as x:y)" ) );
 
   statusBar()->addPermanentWidget( mScaleEdit, 0 );
-  connect( mScaleEdit, SIGNAL( scaleChanged() ), this, SLOT( userScale() ) );
+  connect( mScaleEdit, SIGNAL( scaleChanged( double ) ), this, SLOT( userScale() ) );
 
   if ( QgsMapCanvas::rotationEnabled() )
   {

src/gui/qgsscalecombobox.cpp

@@ -24,7 +24,7 @@
 #include <QSettings>
 #include <QLineEdit>
 
-QgsScaleComboBox::QgsScaleComboBox( QWidget* parent ) : QComboBox( parent ), mScale( 1.0 )
+QgsScaleComboBox::QgsScaleComboBox( QWidget* parent ) : QComboBox( parent ), mScale( 1.0 ), mMinScale( 0.0 )
 {
   updateScales();
 
@@ -126,6 +126,11 @@ bool QgsScaleComboBox::setScaleString( const QString& scaleTxt )
 {
   bool ok;
   double newScale = toDouble( scaleTxt, &ok );
+  double oldScale = mScale;
+  if ( newScale < mMinScale )
+  {
+    newScale = mMinScale;
+  }
   if ( ! ok )
   {
     return false;
@@ -135,12 +140,16 @@ bool QgsScaleComboBox::setScaleString( const QString& scaleTxt )
     mScale = newScale;
     setEditText( toString( mScale ) );
     clearFocus();
+    if ( mScale != oldScale )
+    {
+      emit scaleChanged( mScale );
+    }
     return true;
   }
 }
 
 //! Function to read the selected scale as double
-double QgsScaleComboBox::scale()
+double QgsScaleComboBox::scale() const
 {
   return mScale;
 }
@@ -154,34 +163,24 @@ void QgsScaleComboBox::setScale( double scale )
 //! Slot called when QComboBox has changed
 void QgsScaleComboBox::fixupScale()
 {
-  double newScale;
-  double oldScale = mScale;
-  bool ok, userSetScale;
   QStringList txtList = currentText().split( ':' );
-  userSetScale = txtList.size() != 2;
+  bool userSetScale = txtList.size() != 2;
 
-  // QgsDebugMsg( QString( "entered with oldScale: %1" ).arg( oldScale ) );
-  newScale = toDouble( currentText(), &ok );
+  bool ok;
+  double newScale = toDouble( currentText(), &ok );
 
   // Valid string representation
-  if ( ok && ( newScale != oldScale ) )
+  if ( ok )
   {
     // if a user types scale = 2345, we transform to 1:2345
     if ( userSetScale && newScale >= 1.0 )
     {
-      mScale = 1 / newScale;
+      newScale = 1 / newScale;
     }
-    else
-    {
-      mScale = newScale;
-    }
-    setScale( mScale );
-    emit scaleChanged();
+    setScale( newScale );
   }
   else
   {
-    // Invalid string representation or same scale
-    // Reset to the old
     setScale( mScale );
   }
 }
@@ -241,4 +240,11 @@ double QgsScaleComboBox::toDouble( const QString& scaleString, bool * returnOk )
   return scale;
 }
 
-
+void QgsScaleComboBox::setMinScale( double scale )
+{
+  mMinScale = scale;
+  if ( mScale < scale )
+  {
+    setScale( scale );
+  }
+}

src/gui/qgsscalecombobox.h

@@ -36,9 +36,11 @@ class GUI_EXPORT QgsScaleComboBox : public QComboBox
     //! Function to set the selected scale from text
     bool setScaleString( const QString& scaleTxt );
     //! Function to read the selected scale as double
-    double scale();
+    double scale() const;
     //! Function to set the selected scale from double
     void setScale( double scale );
+    //! Function to read the min scale
+    double minScale() const { return mMinScale; }
 
     //! Helper function to convert a double to scale string
     // Performs rounding, so an exact representation is not to
@@ -49,10 +51,12 @@ class GUI_EXPORT QgsScaleComboBox : public QComboBox
 
   signals:
     //! Signal is emitted when *user* has finished editing/selecting a new scale.
-    void scaleChanged();
+    void scaleChanged( double scale );
 
   public slots:
     void updateScales( const QStringList &scales = QStringList() );
+    //! Function to set the min scale
+    void setMinScale( double scale );
 
   protected:
     void showPopup() override;
@@ -62,6 +66,7 @@ class GUI_EXPORT QgsScaleComboBox : public QComboBox
 
   private:
     double mScale;
+    double mMinScale;
 };
 
 #endif // QGSSCALECOMBOBOX_H

src/gui/qgsscalerangewidget.cpp

@@ -43,6 +43,7 @@ QgsScaleRangeWidget::QgsScaleRangeWidget( QWidget *parent )
 
   mMinimumScaleWidget = new QgsScaleWidget( this );
   mMaximumScaleWidget = new QgsScaleWidget( this );
+  connect( mMinimumScaleWidget, SIGNAL( scaleChanged( double ) ), mMaximumScaleWidget, SLOT( setMinScale( double ) ) );
   mMinimumScaleWidget->setShowCurrentScaleButton( true );
   mMaximumScaleWidget->setShowCurrentScaleButton( true );
   reloadProjectScales();

src/gui/qgsscalewidget.cpp

@@ -37,7 +37,7 @@ QgsScaleWidget::QgsScaleWidget( QWidget *parent )
   layout->addWidget( mCurrentScaleButton );
   mCurrentScaleButton->hide();
 
-  connect( mScaleComboBox, SIGNAL( scaleChanged() ), this, SIGNAL( scaleChanged() ) );
+  connect( mScaleComboBox, SIGNAL( scaleChanged( double ) ), this, SIGNAL( scaleChanged( double ) ) );
   connect( mCurrentScaleButton, SIGNAL( clicked() ), this, SLOT( setScaleFromCanvas() ) );
 }
 

src/gui/qgsscalewidget.h

@@ -32,6 +32,8 @@ class GUI_EXPORT QgsScaleWidget : public QWidget
 {
     Q_OBJECT
     Q_PROPERTY( bool showCurrentScaleButton READ showCurrentScaleButton WRITE setShowCurrentScaleButton )
+    Q_PROPERTY( bool scale READ scale WRITE setScale NOTIFY scaleChanged )
+    Q_PROPERTY( bool minScale READ minScale WRITE setMinScale )
 
   public:
     explicit QgsScaleWidget( QWidget *parent = nullptr );
@@ -51,9 +53,11 @@ class GUI_EXPORT QgsScaleWidget : public QWidget
     //! Function to set the selected scale from text
     bool setScaleString( const QString& scaleTxt ) { return mScaleComboBox->setScaleString( scaleTxt ); }
     //! Function to read the selected scale as double
-    double scale() { return mScaleComboBox->scale();}
+    double scale() const { return mScaleComboBox->scale();}
     //! Function to set the selected scale from double
     void setScale( double scale ) { return mScaleComboBox->setScale( scale ); }
+    //! Function to read the min scale
+    double minScale() const { return mScaleComboBox->minScale(); }
 
     //! Helper function to convert a double to scale string
     // Performs rounding, so an exact representation is not to
@@ -68,9 +72,12 @@ class GUI_EXPORT QgsScaleWidget : public QWidget
     //! assign the current scale from the map canvas
     void setScaleFromCanvas();
 
+    //! Function to set the min scale
+    void setMinScale( double scale ) { mScaleComboBox->setMinScale( scale ); }
+
   signals:
     //! Signal is emitted when *user* has finished editing/selecting a new scale.
-    void scaleChanged();
+    void scaleChanged( double scale );
 
   private:
     QgsScaleComboBox* mScaleComboBox;

src/gui/qgsunitselectionwidget.cpp

@@ -28,8 +28,9 @@ QgsMapUnitScaleDialog::QgsMapUnitScaleDialog( QWidget* parent )
   mSpinBoxMaxSize->setShowClearButton( false );
   connect( mCheckBoxMinScale, SIGNAL( toggled( bool ) ), this, SLOT( configureMinComboBox() ) );
   connect( mCheckBoxMaxScale, SIGNAL( toggled( bool ) ), this, SLOT( configureMaxComboBox() ) );
-  connect( mComboBoxMinScale, SIGNAL( scaleChanged() ), this, SLOT( configureMaxComboBox() ) );
-  connect( mComboBoxMaxScale, SIGNAL( scaleChanged() ), this, SLOT( configureMinComboBox() ) );
+  connect( mComboBoxMinScale, SIGNAL( scaleChanged( double ) ), this, SLOT( configureMaxComboBox() ) );
+  connect( mComboBoxMinScale, SIGNAL( scaleChanged( double ) ), mComboBoxMaxScale, SLOT( setMinScale( double ) ) );
+  connect( mComboBoxMaxScale, SIGNAL( scaleChanged( double ) ), this, SLOT( configureMinComboBox() ) );
 
   connect( mCheckBoxMinSize, SIGNAL( toggled( bool ) ), mSpinBoxMinSize, SLOT( setEnabled( bool ) ) );
   connect( mCheckBoxMaxSize, SIGNAL( toggled( bool ) ), mSpinBoxMaxSize, SLOT( setEnabled( bool ) ) );