Pass proper expression context on to numeric format widget

python/PyQt6/gui/auto_generated/numericformats/qgsnumericformatselectorwidget.sip.in

@@ -40,6 +40,14 @@ Sets the format to show in the widget.
 Returns a new format object representing the settings currently configured in the widget.
 
 The caller takes ownership of the returned object.
+%End
+
+    void registerExpressionContextGenerator( QgsExpressionContextGenerator *generator );
+%Docstring
+Register an expression context generator class that will be used to retrieve
+an expression context for the widget when required.
+
+.. versionadded:: 3.40
 %End
 
   signals:

python/PyQt6/gui/auto_generated/numericformats/qgsnumericformatwidget.sip.in

@@ -8,7 +8,7 @@
 
 
 
-class QgsNumericFormatWidget : QgsPanelWidget
+class QgsNumericFormatWidget : QgsPanelWidget, QgsExpressionContextGenerator
 {
 %Docstring(signature="appended")
 Base class for widgets which allow control over the properties of :py:class:`QgsNumericFormat` subclasses
@@ -42,6 +42,17 @@ Ownership of the returned object is transferred to the caller
 .. seealso:: :py:func:`setFormat`
 %End
 
+    void registerExpressionContextGenerator( QgsExpressionContextGenerator *generator );
+%Docstring
+Register an expression context generator class that will be used to retrieve
+an expression context for the widget when required.
+
+.. versionadded:: 3.40
+%End
+
+    virtual QgsExpressionContext createExpressionContext() const;
+
+
   signals:
 
     void changed();
@@ -305,7 +316,7 @@ Constructor for QgsFractionNumericFormatWidget, initially showing the specified
 
 
 
-class QgsExpressionBasedNumericFormatWidget : QgsNumericFormatWidget, QgsExpressionContextGenerator
+class QgsExpressionBasedNumericFormatWidget : QgsNumericFormatWidget
 {
 %Docstring(signature="appended")
 A widget which allow control over the properties of a :py:class:`QgsExpressionBasedNumericFormat`.

python/gui/auto_generated/numericformats/qgsnumericformatselectorwidget.sip.in

@@ -40,6 +40,14 @@ Sets the format to show in the widget.
 Returns a new format object representing the settings currently configured in the widget.
 
 The caller takes ownership of the returned object.
+%End
+
+    void registerExpressionContextGenerator( QgsExpressionContextGenerator *generator );
+%Docstring
+Register an expression context generator class that will be used to retrieve
+an expression context for the widget when required.
+
+.. versionadded:: 3.40
 %End
 
   signals:

python/gui/auto_generated/numericformats/qgsnumericformatwidget.sip.in

@@ -8,7 +8,7 @@
 
 
 
-class QgsNumericFormatWidget : QgsPanelWidget
+class QgsNumericFormatWidget : QgsPanelWidget, QgsExpressionContextGenerator
 {
 %Docstring(signature="appended")
 Base class for widgets which allow control over the properties of :py:class:`QgsNumericFormat` subclasses
@@ -42,6 +42,17 @@ Ownership of the returned object is transferred to the caller
 .. seealso:: :py:func:`setFormat`
 %End
 
+    void registerExpressionContextGenerator( QgsExpressionContextGenerator *generator );
+%Docstring
+Register an expression context generator class that will be used to retrieve
+an expression context for the widget when required.
+
+.. versionadded:: 3.40
+%End
+
+    virtual QgsExpressionContext createExpressionContext() const;
+
+
   signals:
 
     void changed();
@@ -305,7 +316,7 @@ Constructor for QgsFractionNumericFormatWidget, initially showing the specified
 
 
 
-class QgsExpressionBasedNumericFormatWidget : QgsNumericFormatWidget, QgsExpressionContextGenerator
+class QgsExpressionBasedNumericFormatWidget : QgsNumericFormatWidget
 {
 %Docstring(signature="appended")
 A widget which allow control over the properties of a :py:class:`QgsExpressionBasedNumericFormat`.

src/gui/numericformats/qgsnumericformatselectorwidget.cpp

@@ -75,6 +75,13 @@ QgsNumericFormat *QgsNumericFormatSelectorWidget::format() const
   return mCurrentFormat->clone();
 }
 
+void QgsNumericFormatSelectorWidget::registerExpressionContextGenerator( QgsExpressionContextGenerator *generator )
+{
+  mExpressionContextGenerator = generator;
+  if ( QgsNumericFormatWidget *w = qobject_cast< QgsNumericFormatWidget * >( stackedWidget->currentWidget() ) )
+    w->registerExpressionContextGenerator( mExpressionContextGenerator );
+}
+
 void QgsNumericFormatSelectorWidget::formatTypeChanged()
 {
   const QString newId = mCategoryCombo->currentData().toString();
@@ -142,6 +149,7 @@ void QgsNumericFormatSelectorWidget::updateFormatWidget()
     stackedWidget->setCurrentWidget( w );
     // start receiving updates from widget
     connect( w, &QgsNumericFormatWidget::changed, this, &QgsNumericFormatSelectorWidget::formatChanged );
+    w->registerExpressionContextGenerator( mExpressionContextGenerator );
   }
   else
   {

src/gui/numericformats/qgsnumericformatselectorwidget.h

@@ -23,6 +23,7 @@
 
 class QgsNumericFormat;
 class QgsBasicNumericFormat;
+class QgsExpressionContextGenerator;
 
 
 /**
@@ -56,6 +57,13 @@ class GUI_EXPORT QgsNumericFormatSelectorWidget : public QgsPanelWidget, private
      */
     QgsNumericFormat *format() const SIP_TRANSFERBACK;
 
+    /**
+     * Register an expression context generator class that will be used to retrieve
+     * an expression context for the widget when required.
+     * \since QGIS 3.40
+     */
+    void registerExpressionContextGenerator( QgsExpressionContextGenerator *generator );
+
   signals:
 
     /**
@@ -75,6 +83,8 @@ class GUI_EXPORT QgsNumericFormatSelectorWidget : public QgsPanelWidget, private
 
     std::unique_ptr< QgsNumericFormat > mCurrentFormat;
     std::unique_ptr< QgsBasicNumericFormat > mPreviewFormat;
+
+    QgsExpressionContextGenerator *mExpressionContextGenerator = nullptr;
 };
 
 #endif //QGSNUMERICFORMATSELECTORWIDGET_H

src/gui/numericformats/qgsnumericformatwidget.cpp

@@ -26,6 +26,18 @@
 #include "qgis.h"
 #include <QDialogButtonBox>
 
+void QgsNumericFormatWidget::registerExpressionContextGenerator( QgsExpressionContextGenerator *generator )
+{
+  mExpressionContextGenerator = generator;
+}
+
+QgsExpressionContext QgsNumericFormatWidget::createExpressionContext() const
+{
+  if ( mExpressionContextGenerator )
+    return mExpressionContextGenerator->createExpressionContext();
+  return QgsExpressionContext();
+}
+
 //
 // QgsBasicNumericFormatWidget
 //
@@ -629,7 +641,7 @@ QgsExpressionBasedNumericFormatWidget::QgsExpressionBasedNumericFormatWidget( co
 
 QgsExpressionContext QgsExpressionBasedNumericFormatWidget::createExpressionContext() const
 {
-  QgsExpressionContext context;
+  QgsExpressionContext context = QgsNumericFormatWidget::createExpressionContext();
 
   QgsExpressionContextScope *scope = new QgsExpressionContextScope();
   scope->addVariable( QgsExpressionContextScope::StaticVariable( QStringLiteral( "value" ), 1234.5678 ) );
@@ -653,3 +665,4 @@ QgsNumericFormat *QgsExpressionBasedNumericFormatWidget::format()
 {
   return mFormat->clone();
 }
+

src/gui/numericformats/qgsnumericformatwidget.h

@@ -31,7 +31,7 @@ class QgsExpressionBasedNumericFormat;
  * \brief Base class for widgets which allow control over the properties of QgsNumericFormat subclasses
  * \since QGIS 3.12
  */
-class GUI_EXPORT QgsNumericFormatWidget : public QgsPanelWidget
+class GUI_EXPORT QgsNumericFormatWidget : public QgsPanelWidget, public QgsExpressionContextGenerator
 {
     Q_OBJECT
 
@@ -59,6 +59,16 @@ class GUI_EXPORT QgsNumericFormatWidget : public QgsPanelWidget
      */
     virtual QgsNumericFormat *format() = 0 SIP_TRANSFERBACK;
 
+    /**
+     * Register an expression context generator class that will be used to retrieve
+     * an expression context for the widget when required.
+     *
+     * \since QGIS 3.40
+     */
+    void registerExpressionContextGenerator( QgsExpressionContextGenerator *generator );
+
+    QgsExpressionContext createExpressionContext() const override;
+
   signals:
 
     /**
@@ -66,6 +76,10 @@ class GUI_EXPORT QgsNumericFormatWidget : public QgsPanelWidget
      */
     void changed();
 
+  private:
+
+    QgsExpressionContextGenerator *mExpressionContextGenerator = nullptr;
+
 };
 
 
@@ -367,7 +381,7 @@ class GUI_EXPORT QgsFractionNumericFormatWidget : public QgsNumericFormatWidget,
  * \brief A widget which allow control over the properties of a QgsExpressionBasedNumericFormat.
  * \since QGIS 3.40
  */
-class GUI_EXPORT QgsExpressionBasedNumericFormatWidget : public QgsNumericFormatWidget, public QgsExpressionContextGenerator, private Ui::QgsExpressionBasedNumericFormatWidgetBase
+class GUI_EXPORT QgsExpressionBasedNumericFormatWidget : public QgsNumericFormatWidget, private Ui::QgsExpressionBasedNumericFormatWidgetBase
 {
     Q_OBJECT
 

src/gui/symbology/qgssymbollayerwidget.cpp

@@ -5684,6 +5684,7 @@ void QgsLinearReferencingSymbolLayerWidget::changeNumberFormat()
     QgsNumericFormatSelectorWidget *widget = new QgsNumericFormatSelectorWidget( this );
     widget->setPanelTitle( tr( "Number Format" ) );
     widget->setFormat( mLayer->numericFormat() );
+    widget->registerExpressionContextGenerator( this );
     connect( widget, &QgsNumericFormatSelectorWidget::changed, this, [ = ]
     {
       if ( !mBlockChangesSignal )