Fix impossible to activate draw effects on settings in font buttons

If we ignore the enabled state when testing whether a paint effect
should be saved, then we get stuck in a loop where first enabling
the effect still reports the stack as a default stack so the widget
immediately unchecks itself and it's impossible for users to actually
modify the stack and make it definitely non-default!

src/gui/qgstextformatwidget.cpp

@@ -1039,7 +1039,7 @@ QgsTextFormat QgsTextFormatWidget::format( bool includeDataDefinedProperties ) c
   buffer.setJoinStyle( mBufferJoinStyleComboBox->penJoinStyle() );
   buffer.setFillBufferInterior( mBufferTranspFillChbx->isChecked() );
   buffer.setBlendMode( comboBufferBlendMode->blendMode() );
-  if ( mBufferEffect && !QgsPaintEffectRegistry::isDefaultStack( mBufferEffect.get() ) )
+  if ( mBufferEffect && ( !QgsPaintEffectRegistry::isDefaultStack( mBufferEffect.get() ) || mBufferEffect->enabled() ) )
     buffer.setPaintEffect( mBufferEffect->clone() );
   else
     buffer.setPaintEffect( nullptr );
@@ -1053,7 +1053,7 @@ QgsTextFormat QgsTextFormatWidget::format( bool includeDataDefinedProperties ) c
   mask.setSizeUnit( mMaskBufferUnitWidget->unit() );
   mask.setSizeMapUnitScale( mMaskBufferUnitWidget->getMapUnitScale() );
   mask.setJoinStyle( mMaskJoinStyleComboBox->penJoinStyle() );
-  if ( mMaskEffect && !QgsPaintEffectRegistry::isDefaultStack( mMaskEffect.get() ) )
+  if ( mMaskEffect && ( !QgsPaintEffectRegistry::isDefaultStack( mMaskEffect.get() ) || mMaskEffect->enabled() ) )
     mask.setPaintEffect( mMaskEffect->clone() );
   else
     mask.setPaintEffect( nullptr );
@@ -1086,7 +1086,7 @@ QgsTextFormat QgsTextFormatWidget::format( bool includeDataDefinedProperties ) c
   background.setJoinStyle( mShapePenStyleCmbBx->penJoinStyle() );
   background.setOpacity( mBackgroundOpacityWidget->opacity() );
   background.setBlendMode( mShapeBlendCmbBx->blendMode() );
-  if ( mBackgroundEffect && !QgsPaintEffectRegistry::isDefaultStack( mBackgroundEffect.get() ) )
+  if ( mBackgroundEffect && ( !QgsPaintEffectRegistry::isDefaultStack( mBackgroundEffect.get() ) || mBackgroundEffect->enabled() ) )
     background.setPaintEffect( mBackgroundEffect->clone() );
   else
     background.setPaintEffect( nullptr );

src/gui/vector/qgsdiagramproperties.cpp

@@ -882,7 +882,7 @@ void QgsDiagramProperties::apply()
   ds.setSpacingUnit( mBarSpacingUnitComboBox->unit() );
   ds.setSpacingMapUnitScale( mBarSpacingUnitComboBox->getMapUnitScale() );
 
-  if ( mPaintEffect && !QgsPaintEffectRegistry::isDefaultStack( mPaintEffect.get() ) )
+  if ( mPaintEffect && ( !QgsPaintEffectRegistry::isDefaultStack( mPaintEffect.get() ) || mPaintEffect->enabled() ) )
     ds.setPaintEffect( mPaintEffect->clone() );
   else
     ds.setPaintEffect( nullptr );