When setting a new text format for a QgsFontButton, automatically

update any open configuration panel to reflect the new format
(or dismiss it automatically if the new format is invalid)

Avoids UI going out of sync with text formats when a panel is already
open

python/gui/auto_generated/qgsfontbutton.sip.in

@@ -9,6 +9,7 @@
 
 
 
+
 class QgsFontButton : QToolButton
 {
 %Docstring

python/gui/auto_generated/qgstextformatwidget.sip.in

@@ -277,6 +277,13 @@ Constructor for QgsTextFormatPanelWidget.
     QgsTextFormat format() const;
 %Docstring
 Returns the current formatting settings defined by the widget.
+%End
+
+    void setFormat( const QgsTextFormat &format );
+%Docstring
+Sets the ``format`` to show in the widget.
+
+.. versionadded:: 3.16
 %End
 
     void setContext( const QgsSymbolWidgetContext &context );

src/gui/qgsfontbutton.cpp

@@ -94,12 +94,12 @@ void QgsFontButton::showSettingsDialog()
       QgsPanelWidget *panel = QgsPanelWidget::findParentPanel( this );
       if ( panel && panel->dockMode() )
       {
-        QgsTextFormatPanelWidget *formatWidget = new QgsTextFormatPanelWidget( mFormat, mMapCanvas, this, mLayer.data() );
-        formatWidget->setPanelTitle( mDialogTitle );
-        formatWidget->setContext( symbolContext );
+        mActivePanel = new QgsTextFormatPanelWidget( mFormat, mMapCanvas, this, mLayer.data() );
+        mActivePanel->setPanelTitle( mDialogTitle );
+        mActivePanel->setContext( symbolContext );
 
-        connect( formatWidget, &QgsTextFormatPanelWidget::widgetChanged, this, [ this, formatWidget ] { this->setTextFormat( formatWidget->format() ); } );
-        panel->openPanel( formatWidget );
+        connect( mActivePanel, &QgsTextFormatPanelWidget::widgetChanged, this, [ this ] { setTextFormat( mActivePanel->format() ); } );
+        panel->openPanel( mActivePanel );
         return;
       }
 
@@ -154,8 +154,14 @@ QgsMessageBar *QgsFontButton::messageBar() const
 
 void QgsFontButton::setTextFormat( const QgsTextFormat &format )
 {
+  if ( mActivePanel && !format.isValid() )
+    mActivePanel->acceptPanel();
+
   mFormat = format;
   updatePreview();
+
+  if ( mActivePanel && format.isValid() )
+    mActivePanel->setFormat( format );
   emit changed();
 }
 

src/gui/qgsfontbutton.h

@@ -24,6 +24,8 @@
 class QgsExpressionContextGenerator;
 class QgsMapCanvas;
 class QgsMessageBar;
+class QgsTextFormatPanelWidget;
+
 
 /**
  * \ingroup gui
@@ -329,6 +331,7 @@ class GUI_EXPORT QgsFontButton : public QToolButton
     bool mShowNoFormat = false;
     QString mNullFormatString;
     QPointer< QAction > mNullFormatAction;
+    QPointer< QgsTextFormatPanelWidget > mActivePanel;
 
     /**
      * Attempts to parse \a mimeData as a text format.

src/gui/qgstextformatwidget.cpp

@@ -2036,14 +2036,25 @@ QgsTextFormatPanelWidget::QgsTextFormatPanelWidget( const QgsTextFormat &format,
   : QgsPanelWidgetWrapper( new QgsTextFormatWidget( format, mapCanvas, nullptr, layer ), parent )
 {
   mFormatWidget = qobject_cast< QgsTextFormatWidget * >( widget() );
-  connect( mFormatWidget, &QgsTextFormatWidget::widgetChanged, this, &QgsPanelWidget::widgetChanged );
+  connect( mFormatWidget, &QgsTextFormatWidget::widgetChanged, this, [ = ]
+  {
+    if ( !mBlockSignals )
+      emit widgetChanged();
+  } );
 }
 
 QgsTextFormat QgsTextFormatPanelWidget::format() const
 {
   return mFormatWidget->format();
 }
 
+void QgsTextFormatPanelWidget::setFormat( const QgsTextFormat &format )
+{
+  mBlockSignals = true;
+  mFormatWidget->setFormat( format );
+  mBlockSignals = false;
+}
+
 void QgsTextFormatPanelWidget::setContext( const QgsSymbolWidgetContext &context )
 {
   mFormatWidget->setContext( context );

src/gui/qgstextformatwidget.h

@@ -395,6 +395,13 @@ class GUI_EXPORT QgsTextFormatPanelWidget : public QgsPanelWidgetWrapper
      */
     QgsTextFormat format() const;
 
+    /**
+     * Sets the \a format to show in the widget.
+     *
+     * \since QGIS 3.16
+     */
+    void setFormat( const QgsTextFormat &format );
+
     /**
      * Sets the \a context in which the widget is shown, e.g., the associated map canvas and expression contexts.
      * \since QGIS 3.10
@@ -406,6 +413,7 @@ class GUI_EXPORT QgsTextFormatPanelWidget : public QgsPanelWidgetWrapper
   private:
 
     QgsTextFormatWidget *mFormatWidget = nullptr;
+    bool mBlockSignals = false;
 };
 
 #endif //QGSTEXTFORMATWIDGET_H