Store elevation filter fixed range size in project

Remember this setting between sessions for a project

python/PyQt6/core/auto_generated/project/qgsprojectelevationproperties.sip.in

@@ -84,6 +84,34 @@ elevation limits associated with the project.
 .. seealso:: :py:func:`elevationRangeChanged`
 
 
+.. versionadded:: 3.38
+%End
+
+    void setElevationFilterRangeSize( double size );
+%Docstring
+Sets the fixed size for elevation range filtering in the project, used when interactively filtering by elevation.
+
+Set to -1 if no fixed elevation range size is desired.
+
+A fixed size forces the selected elevation range to have a matching difference between
+the upper and lower elevation.
+
+.. seealso:: :py:func:`elevationFilterRangeSize`
+
+.. versionadded:: 3.38
+%End
+
+    double elevationFilterRangeSize() const;
+%Docstring
+Returns the fixed size for elevation range filtering in the project, used when interactively filtering by elevation.
+
+Returns -1 if no fixed elevation range size is desired.
+
+A fixed size forces the selected elevation range to have a matching difference between
+the upper and lower elevation.
+
+.. seealso:: :py:func:`setElevationFilterRangeSize`
+
 .. versionadded:: 3.38
 %End
 

python/PyQt6/gui/auto_generated/elevation/qgselevationcontrollerwidget.sip.in

@@ -112,6 +112,8 @@ A fixed size forces the selected elevation range to have a matching difference b
 the upper and lower elevation.
 
 .. seealso:: :py:func:`fixedRangeSize`
+
+.. seealso:: :py:func:`fixedRangeSizeChanged`
 %End
 
   signals:
@@ -123,6 +125,15 @@ Emitted when the visible range from the widget is changed.
 .. seealso:: :py:func:`setRange`
 
 .. seealso:: :py:func:`range`
+%End
+
+    void fixedRangeSizeChanged( double size );
+%Docstring
+Emitted when the fixed range size is changed from the widget.
+
+.. seealso:: :py:func:`fixedRangeSize`
+
+.. seealso:: :py:func:`setFixedRangeSize`
 %End
 
 };

python/core/auto_generated/project/qgsprojectelevationproperties.sip.in

@@ -84,6 +84,34 @@ elevation limits associated with the project.
 .. seealso:: :py:func:`elevationRangeChanged`
 
 
+.. versionadded:: 3.38
+%End
+
+    void setElevationFilterRangeSize( double size );
+%Docstring
+Sets the fixed size for elevation range filtering in the project, used when interactively filtering by elevation.
+
+Set to -1 if no fixed elevation range size is desired.
+
+A fixed size forces the selected elevation range to have a matching difference between
+the upper and lower elevation.
+
+.. seealso:: :py:func:`elevationFilterRangeSize`
+
+.. versionadded:: 3.38
+%End
+
+    double elevationFilterRangeSize() const;
+%Docstring
+Returns the fixed size for elevation range filtering in the project, used when interactively filtering by elevation.
+
+Returns -1 if no fixed elevation range size is desired.
+
+A fixed size forces the selected elevation range to have a matching difference between
+the upper and lower elevation.
+
+.. seealso:: :py:func:`setElevationFilterRangeSize`
+
 .. versionadded:: 3.38
 %End
 

python/gui/auto_generated/elevation/qgselevationcontrollerwidget.sip.in

@@ -112,6 +112,8 @@ A fixed size forces the selected elevation range to have a matching difference b
 the upper and lower elevation.
 
 .. seealso:: :py:func:`fixedRangeSize`
+
+.. seealso:: :py:func:`fixedRangeSizeChanged`
 %End
 
   signals:
@@ -123,6 +125,15 @@ Emitted when the visible range from the widget is changed.
 .. seealso:: :py:func:`setRange`
 
 .. seealso:: :py:func:`range`
+%End
+
+    void fixedRangeSizeChanged( double size );
+%Docstring
+Emitted when the fixed range size is changed from the widget.
+
+.. seealso:: :py:func:`fixedRangeSize`
+
+.. seealso:: :py:func:`setFixedRangeSize`
 %End
 
 };

src/app/canvas/qgsappcanvasfiltering.cpp

@@ -15,6 +15,7 @@
 
 #include "qgsappcanvasfiltering.h"
 #include "qgselevationcontrollerwidget.h"
+#include "qgsprojectelevationproperties.h"
 #include "qgsmapcanvas.h"
 #include "qgisapp.h"
 #include <QInputDialog>
@@ -58,6 +59,16 @@ void QgsAppCanvasFiltering::setupElevationControllerAction( QAction *action, Qgs
       {
         mCanvasElevationControllerMap.remove( canvas );
       } );
+
+      if ( canvas == QgisApp::instance()->mapCanvas() )
+      {
+        // for main canvas, attach settings to project settings
+        controller->setFixedRangeSize( QgsProject::instance()->elevationProperties()->elevationFilterRangeSize() );
+        connect( controller, &QgsElevationControllerWidget::fixedRangeSizeChanged, this, []( double size )
+        {
+          QgsProject::instance()->elevationProperties()->setElevationFilterRangeSize( size );
+        } );
+      }
     }
     else
     {

src/core/project/qgsprojectelevationproperties.cpp

@@ -76,6 +76,10 @@ bool QgsProjectElevationProperties::readXml( const QDomElement &element, const Q
     rangeUpper = storedRangeUpper;
   mElevationRange = QgsDoubleRange( rangeLower, rangeUpper );
 
+  mElevationFilterRangeSize = element.attribute( QStringLiteral( "FilterRangeSize" ) ).toDouble( &ok );
+  if ( !ok )
+    mElevationFilterRangeSize = -1;
+
   emit changed();
   emit elevationRangeChanged( mElevationRange );
   return true;
@@ -98,6 +102,10 @@ QDomElement QgsProjectElevationProperties::writeXml( QDomDocument &document, con
   if ( mElevationRange.upper() != std::numeric_limits< double >::max() )
     element.setAttribute( QStringLiteral( "RangeUpper" ), qgsDoubleToString( mElevationRange.upper() ) );
 
+  if ( mElevationFilterRangeSize >= 0 )
+  {
+    element.setAttribute( QStringLiteral( "FilterRangeSize" ), mElevationFilterRangeSize );
+  }
   return element;
 }
 
@@ -118,6 +126,15 @@ void QgsProjectElevationProperties::setTerrainProvider( QgsAbstractTerrainProvid
     emit changed();
 }
 
+void QgsProjectElevationProperties::setElevationFilterRangeSize( double size )
+{
+  if ( mElevationFilterRangeSize == size )
+    return;
+
+  mElevationFilterRangeSize = size;
+  emit changed();
+}
+
 void QgsProjectElevationProperties::setElevationRange( const QgsDoubleRange &range )
 {
   if ( mElevationRange == range )

src/core/project/qgsprojectelevationproperties.h

@@ -100,6 +100,34 @@ class CORE_EXPORT QgsProjectElevationProperties : public QObject
      */
     QgsDoubleRange elevationRange() const { return mElevationRange; }
 
+    /**
+     * Sets the fixed size for elevation range filtering in the project, used when interactively filtering by elevation.
+     *
+     * Set to -1 if no fixed elevation range size is desired.
+     *
+     * A fixed size forces the selected elevation range to have a matching difference between
+     * the upper and lower elevation.
+     *
+     * \see elevationFilterRangeSize()
+     *
+     * \since QGIS 3.38
+     */
+    void setElevationFilterRangeSize( double size );
+
+    /**
+     * Returns the fixed size for elevation range filtering in the project, used when interactively filtering by elevation.
+     *
+     * Returns -1 if no fixed elevation range size is desired.
+     *
+     * A fixed size forces the selected elevation range to have a matching difference between
+     * the upper and lower elevation.
+     *
+     * \see setElevationFilterRangeSize()
+     *
+     * \since QGIS 3.38
+     */
+    double elevationFilterRangeSize() const { return mElevationFilterRangeSize; }
+
   public slots:
 
     /**
@@ -140,6 +168,7 @@ class CORE_EXPORT QgsProjectElevationProperties : public QObject
 
     std::unique_ptr< QgsAbstractTerrainProvider > mTerrainProvider;
     QgsDoubleRange mElevationRange;
+    double mElevationFilterRangeSize = -1;
 
 };
 

src/gui/elevation/qgselevationcontrollerwidget.cpp

@@ -49,11 +49,11 @@ QgsElevationControllerWidget::QgsElevationControllerWidget( QWidget *parent )
   mMenu = new QMenu( this );
   mConfigureButton->setMenu( mMenu );
 
-  QgsElevationControllerSettingsAction *settingsAction = new QgsElevationControllerSettingsAction( mMenu );
-  mMenu->addAction( settingsAction );
+  mSettingsAction = new QgsElevationControllerSettingsAction( mMenu );
+  mMenu->addAction( mSettingsAction );
 
-  settingsAction->sizeSpin()->clear();
-  connect( settingsAction->sizeSpin(), qOverload< double >( &QgsDoubleSpinBox::valueChanged ), this, [this]( double size )
+  mSettingsAction->sizeSpin()->clear();
+  connect( mSettingsAction->sizeSpin(), qOverload< double >( &QgsDoubleSpinBox::valueChanged ), this, [this]( double size )
   {
     setFixedRangeSize( size < 0 ? -1 : size );
   } );
@@ -225,6 +225,9 @@ void QgsElevationControllerWidget::setFixedRangeSize( double size )
   {
     mSlider->setFixedRangeSize( static_cast< int >( std::round( mFixedRangeSize * mSliderPrecision ) ) );
   }
+  if ( mFixedRangeSize != mSettingsAction->sizeSpin()->value() )
+    mSettingsAction->sizeSpin()->setValue( mFixedRangeSize );
+  emit fixedRangeSizeChanged( mFixedRangeSize );
 }
 
 //

src/gui/elevation/qgselevationcontrollerwidget.h

@@ -149,6 +149,7 @@ class GUI_EXPORT QgsElevationControllerWidget : public QWidget
      * the upper and lower elevation.
      *
      * \see fixedRangeSize()
+     * \see fixedRangeSizeChanged()
      */
     void setFixedRangeSize( double size );
 
@@ -162,11 +163,20 @@ class GUI_EXPORT QgsElevationControllerWidget : public QWidget
      */
     void rangeChanged( const QgsDoubleRange &range );
 
+    /**
+     * Emitted when the fixed range size is changed from the widget.
+     *
+     * \see fixedRangeSize()
+     * \see setFixedRangeSize()
+     */
+    void fixedRangeSizeChanged( double size );
+
   private:
 
     void updateWidgetMask();
 
     QToolButton *mConfigureButton = nullptr;
+    QgsElevationControllerSettingsAction *mSettingsAction = nullptr;
     QMenu *mMenu = nullptr;
     QgsRangeSlider *mSlider = nullptr;
     QgsElevationControllerLabels *mSliderLabels = nullptr;