[ui] Fix broken text annotation background color

src/app/qgsannotationwidget.cpp

@@ -74,6 +74,18 @@ QgsAnnotationWidget::QgsAnnotationWidget( QgsMapCanvasAnnotationItem *item, QWid
   mMapMarkerButton->setMessageBar( QgisApp::instance()->messageBar() );
   mFrameStyleButton->setMapCanvas( QgisApp::instance()->mapCanvas() );
   mFrameStyleButton->setMessageBar( QgisApp::instance()->messageBar() );
+
+  connect( mFrameStyleButton, &QgsSymbolButton::changed, this, &QgsAnnotationWidget::frameStyleChanged );
+}
+
+QColor QgsAnnotationWidget::backgroundColor()
+{
+  return mFrameStyleButton->symbol() ? mFrameStyleButton->symbol()->color() : QColor();
+}
+
+void QgsAnnotationWidget::frameStyleChanged()
+{
+  emit backgroundColorChanged( backgroundColor() );
 }
 
 void QgsAnnotationWidget::apply()

src/app/qgsannotationwidget.h

@@ -33,16 +33,25 @@ class APP_EXPORT QgsAnnotationWidget: public QWidget, private Ui::QgsAnnotationW
 {
     Q_OBJECT
   public:
+
     QgsAnnotationWidget( QgsMapCanvasAnnotationItem *item, QWidget *parent = nullptr, Qt::WindowFlags f = nullptr );
 
+    //! Returns the annotation frame symbol fill color
+    QColor backgroundColor();
+
     void apply();
 
+  private:
+
+    void frameStyleChanged();
+
   signals:
 
     //! Emitted when the background color of the annotation is changed
     void backgroundColorChanged( const QColor &color );
 
   private:
+
     QgsMapCanvasAnnotationItem *mItem = nullptr;
 
     void blockAllSignals( bool block );

src/app/qgstextannotationdialog.cpp

@@ -38,7 +38,7 @@ QgsTextAnnotationDialog::QgsTextAnnotationDialog( QgsMapCanvasAnnotationItem *it
   mStackedWidget->addWidget( mEmbeddedWidget );
   mStackedWidget->setCurrentWidget( mEmbeddedWidget );
   connect( mEmbeddedWidget, &QgsAnnotationWidget::backgroundColorChanged, this, &QgsTextAnnotationDialog::backgroundColorChanged );
-  mTextEdit->setAttribute( Qt::WA_TranslucentBackground );
+
   if ( mItem && mItem->annotation() )
   {
     QgsTextAnnotation *annotation = static_cast< QgsTextAnnotation * >( mItem->annotation() );
@@ -53,6 +53,7 @@ QgsTextAnnotationDialog::QgsTextAnnotationDialog( QgsMapCanvasAnnotationItem *it
   mFontColorButton->setContext( QStringLiteral( "symbology" ) );
 
   setCurrentFontPropertiesToGui();
+  backgroundColorChanged( mEmbeddedWidget->backgroundColor() );
 
   QObject::connect( mButtonBox, &QDialogButtonBox::accepted, this, &QgsTextAnnotationDialog::applyTextToItem );
   QObject::connect( mButtonBox, &QDialogButtonBox::helpRequested, this, &QgsTextAnnotationDialog::showHelp );
@@ -86,6 +87,7 @@ void QgsTextAnnotationDialog::backgroundColorChanged( const QColor &color )
   QPalette p = mTextEdit->viewport()->palette();
   p.setColor( QPalette::Base, color );
   mTextEdit->viewport()->setPalette( p );
+  mTextEdit->setStyleSheet( QStringLiteral( "QTextEdit { background-color: %1; }" ).arg( color.name() ) );
 }
 
 void QgsTextAnnotationDialog::applyTextToItem()