[bugfix] Allow empty null representation in spinboxes

Fixes #18583 - Widget "Range": Representation for NULL value is NOT always displayed correctly

python/gui/auto_generated/editorwidgets/qgsdoublespinbox.sip.in

@@ -124,6 +124,13 @@ Returns the value used when clear() is called.
 Set alignment in the embedded line edit widget
 
 :param alignment:
+%End
+
+    void setSpecialValueText( const QString &txt );
+%Docstring
+Set the special-value text to be ``txt``
+If set, the spin box will display this text instead of a numeric value whenever the current value
+is equal to minimum(). Typical use is to indicate that this choice has a special (default) meaning.
 %End
 
     virtual double valueFromText( const QString &text ) const;

python/gui/auto_generated/editorwidgets/qgsspinbox.sip.in

@@ -124,6 +124,13 @@ Returns the value used when clear() is called.
 Set alignment in the embedded line edit widget
 
 :param alignment:
+%End
+
+    void setSpecialValueText( const QString &txt );
+%Docstring
+Set the special-value text to be ``txt``
+If set, the spin box will display this text instead of a numeric value whenever the current value
+is equal to minimum(). Typical use is to indicate that this choice has a special (default) meaning.
 %End
 
     virtual int valueFromText( const QString &text ) const;

src/gui/editorwidgets/qgsdoublespinbox.cpp

@@ -26,6 +26,12 @@
 
 #define CLEAR_ICON_SIZE 16
 
+// This is required because private implementation of
+// QAbstractSpinBoxPrivate checks for specialText emptiness
+// and skips specialText handling if it's empty
+QString QgsDoubleSpinBox::SPECIAL_TEXT_WHEN_EMPTY = QChar( 0x2063 );
+
+
 QgsDoubleSpinBox::QgsDoubleSpinBox( QWidget *parent )
   : QDoubleSpinBox( parent )
 {
@@ -140,13 +146,24 @@ void QgsDoubleSpinBox::setLineEditAlignment( Qt::Alignment alignment )
   mLineEdit->setAlignment( alignment );
 }
 
+void QgsDoubleSpinBox::setSpecialValueText( const QString &txt )
+{
+  if ( txt.isEmpty() )
+    QDoubleSpinBox::setSpecialValueText( SPECIAL_TEXT_WHEN_EMPTY );
+  else
+    QDoubleSpinBox::setSpecialValueText( txt );
+}
+
 QString QgsDoubleSpinBox::stripped( const QString &originalText ) const
 {
   //adapted from QAbstractSpinBoxPrivate::stripped
   //trims whitespace, prefix and suffix from spin box text
   QString text = originalText;
   if ( specialValueText().isEmpty() || text != specialValueText() )
   {
+    // Strip SPECIAL_TEXT_WHEN_EMPTY
+    if ( text.contains( SPECIAL_TEXT_WHEN_EMPTY ) )
+      text = text.replace( SPECIAL_TEXT_WHEN_EMPTY, QString() );
     int from = 0;
     int size = text.size();
     bool changed = false;

src/gui/editorwidgets/qgsdoublespinbox.h

@@ -132,6 +132,13 @@ class GUI_EXPORT QgsDoubleSpinBox : public QDoubleSpinBox
      */
     void setLineEditAlignment( Qt::Alignment alignment );
 
+    /**
+     * Set the special-value text to be \a txt
+     * If set, the spin box will display this text instead of a numeric value whenever the current value
+     * is equal to minimum(). Typical use is to indicate that this choice has a special (default) meaning.
+     */
+    void setSpecialValueText( const QString &txt );
+
     double valueFromText( const QString &text ) const override;
     QValidator::State validate( QString &input, int &pos ) const override;
     void paintEvent( QPaintEvent *e ) override;
@@ -156,6 +163,13 @@ class GUI_EXPORT QgsDoubleSpinBox : public QDoubleSpinBox
     bool mExpressionsEnabled = true;
 
     QString stripped( const QString &originalText ) const;
+
+    // This is required because private implementation of
+    // QAbstractSpinBoxPrivate checks for specialText emptiness
+    // and skips specialText handling if it's empty
+    static QString SPECIAL_TEXT_WHEN_EMPTY;
+
+    friend class TestQgsRangeWidgetWrapper;
 };
 
 #endif // QGSDOUBLESPINBOX_H

src/gui/editorwidgets/qgsrangewidgetwrapper.cpp

@@ -22,6 +22,8 @@
 #include "qgsdial.h"
 #include "qgsslider.h"
 
+
+
 QgsRangeWidgetWrapper::QgsRangeWidgetWrapper( QgsVectorLayer *vl, int fieldIdx, QWidget *editor, QWidget *parent )
   : QgsEditorWidgetWrapper( vl, fieldIdx, editor, parent )
 
@@ -119,7 +121,11 @@ void QgsRangeWidgetWrapper::initWidget( QWidget *editor )
       // Note: call setMinimum here or setValue won't work
       mDoubleSpinBox->setMinimum( minval );
       mDoubleSpinBox->setValue( minval );
-      mDoubleSpinBox->setSpecialValueText( QgsApplication::nullRepresentation() );
+      QgsDoubleSpinBox *doubleSpinBox( qobject_cast<QgsDoubleSpinBox *>( mDoubleSpinBox ) );
+      if ( doubleSpinBox )
+        doubleSpinBox->setSpecialValueText( QgsApplication::nullRepresentation() );
+      else
+        mDoubleSpinBox->setSpecialValueText( QgsApplication::nullRepresentation() );
     }
     mDoubleSpinBox->setMinimum( minval );
     mDoubleSpinBox->setMaximum( maxval );
@@ -141,7 +147,11 @@ void QgsRangeWidgetWrapper::initWidget( QWidget *editor )
       int stepval = step.isValid() ? step.toInt() : 1;
       minval -= stepval;
       mIntSpinBox->setValue( minval );
-      mIntSpinBox->setSpecialValueText( QgsApplication::nullRepresentation() );
+      QgsSpinBox *intSpinBox( qobject_cast<QgsSpinBox *>( mIntSpinBox ) );
+      if ( intSpinBox )
+        intSpinBox->setSpecialValueText( QgsApplication::nullRepresentation() );
+      else
+        mIntSpinBox->setSpecialValueText( QgsApplication::nullRepresentation() );
     }
     setupIntEditor( minval, max, step, mIntSpinBox, this );
     if ( config( QStringLiteral( "Suffix" ) ).isValid() )

src/gui/editorwidgets/qgsspinbox.cpp

@@ -26,6 +26,12 @@
 
 #define CLEAR_ICON_SIZE 16
 
+// This is required because private implementation of
+// QAbstractSpinBoxPrivate checks for specialText emptiness
+// and skips specialText handling if it's empty
+QString QgsSpinBox::SPECIAL_TEXT_WHEN_EMPTY = QChar( 0x2063 );
+
+
 QgsSpinBox::QgsSpinBox( QWidget *parent )
   : QSpinBox( parent )
 {
@@ -137,6 +143,14 @@ void QgsSpinBox::setLineEditAlignment( Qt::Alignment alignment )
   mLineEdit->setAlignment( alignment );
 }
 
+void QgsSpinBox::setSpecialValueText( const QString &txt )
+{
+  if ( txt.isEmpty() )
+    QSpinBox::setSpecialValueText( SPECIAL_TEXT_WHEN_EMPTY );
+  else
+    QSpinBox::setSpecialValueText( txt );
+}
+
 int QgsSpinBox::valueFromText( const QString &text ) const
 {
   if ( !mExpressionsEnabled )
@@ -185,6 +199,9 @@ QString QgsSpinBox::stripped( const QString &originalText ) const
   QString text = originalText;
   if ( specialValueText().isEmpty() || text != specialValueText() )
   {
+    // Strip SPECIAL_TEXT_WHEN_EMPTY
+    if ( text.contains( SPECIAL_TEXT_WHEN_EMPTY ) )
+      text = text.replace( SPECIAL_TEXT_WHEN_EMPTY, QString() );
     int from = 0;
     int size = text.size();
     bool changed = false;

src/gui/editorwidgets/qgsspinbox.h

@@ -132,6 +132,13 @@ class GUI_EXPORT QgsSpinBox : public QSpinBox
      */
     void setLineEditAlignment( Qt::Alignment alignment );
 
+    /**
+     * Set the special-value text to be \a txt
+     * If set, the spin box will display this text instead of a numeric value whenever the current value
+     * is equal to minimum(). Typical use is to indicate that this choice has a special (default) meaning.
+     */
+    void setSpecialValueText( const QString &txt );
+
     int valueFromText( const QString &text ) const override;
     QValidator::State validate( QString &input, int &pos ) const override;
 
@@ -156,7 +163,15 @@ class GUI_EXPORT QgsSpinBox : public QSpinBox
 
     bool mExpressionsEnabled = true;
 
+    // This is required because private implementation of
+    // QAbstractSpinBoxPrivate checks for specialText emptiness
+    // and skips specialText handling if it's empty
+    static QString SPECIAL_TEXT_WHEN_EMPTY;
+
     QString stripped( const QString &originalText ) const;
+
+    friend class TestQgsRangeWidgetWrapper;
+
 };
 
 #endif // QGSSPINBOX_H