Block the events while showing a dialog

When showing a file dialog, Qt can choose to use the "system" file
dialog, which will make QgsExternalResourceWidget to loose the focus.
This patch blocks all the events that are sent to
QgsExternalResourceWidget while a dialog is shown, this way it will keep
the focus until the dialog is closed.

Sponsored by the QGIS project (qgis.org)

Fixes: #26948

python/gui/auto_generated/qgsexternalresourcewidget.sip.in

@@ -141,6 +141,10 @@ is set to QgsFileWidget.RelativeDefaultPath.
 emitteed as soon as the current document changes
 %End
 
+  protected:
+    virtual bool eventFilter( QObject *watched, QEvent *event );
+
+
 };
 
 /************************************************************************

python/gui/auto_generated/qgsfilewidget.sip.in

@@ -189,6 +189,7 @@ the appearance and behavior of the line edit portion of the widget.
 emitted as soon as the current file or directory is changed
 %End
 
+
 };
 
 

src/gui/editorwidgets/qgsexternalresourcewidgetwrapper.cpp

@@ -175,8 +175,7 @@ void QgsExternalResourceWidgetWrapper::initWidget( QWidget *editor )
     }
     if ( cfg.contains( QStringLiteral( "FileWidgetButton" ) ) )
     {
-      // Prevent from showing the button in the attribute table, see https://github.com/qgis/QGIS/issues/26948
-      mQgsWidget->fileWidget()->setFileWidgetButtonVisible( cfg.value( QStringLiteral( "FileWidgetButton" ) ).toBool() && context().formMode() != QgsAttributeEditorContext::Popup );
+      mQgsWidget->fileWidget()->setFileWidgetButtonVisible( cfg.value( QStringLiteral( "FileWidgetButton" ) ).toBool() );
     }
     if ( cfg.contains( QStringLiteral( "DocumentViewer" ) ) )
     {

src/gui/qgsexternalresourcewidget.cpp

@@ -55,6 +55,17 @@ QgsExternalResourceWidget::QgsExternalResourceWidget( QWidget *parent )
 
   connect( mFileWidget, &QgsFileWidget::fileChanged, this, &QgsExternalResourceWidget::loadDocument );
   connect( mFileWidget, &QgsFileWidget::fileChanged, this, &QgsExternalResourceWidget::valueChanged );
+  connect( mFileWidget, &QgsFileWidget::blockEvents, this, [this]( bool block )
+  {
+    if ( block )
+    {
+      installEventFilter( this );
+    }
+    else
+    {
+      removeEventFilter( this );
+    }
+  } );
 }
 
 QVariant QgsExternalResourceWidget::documentPath( QVariant::Type type ) const
@@ -194,6 +205,15 @@ void QgsExternalResourceWidget::setDefaultRoot( const QString &defaultRoot )
   mDefaultRoot = defaultRoot;
 }
 
+bool QgsExternalResourceWidget::eventFilter( QObject *watched, QEvent *event )
+{
+  if ( watched == this && event && ( event->type() == QEvent::FocusOut ||  event->type() == QEvent::FocusAboutToChange ) )
+  {
+    return true;
+  }
+  return QWidget::eventFilter( watched, event );
+}
+
 QgsFileWidget::RelativeStorage QgsExternalResourceWidget::relativeStorage() const
 {
   return mRelativeStorage;
@@ -246,5 +266,3 @@ void QgsExternalResourceWidget::loadDocument( const QString &path )
     }
   }
 }
-
-

src/gui/qgsexternalresourcewidget.h

@@ -147,6 +147,10 @@ class GUI_EXPORT QgsExternalResourceWidget : public QWidget
     //! emitteed as soon as the current document changes
     void valueChanged( const QString & );
 
+  protected:
+    // Needed to block events when showing a dialog
+    bool eventFilter( QObject *watched, QEvent *event ) override;
+
   private slots:
     void loadDocument( const QString &path );
 

src/gui/qgsfilewidget.cpp

@@ -255,6 +255,7 @@ void QgsFileWidget::openFileDialog()
   QStringList fileNames;
   QString title;
 
+  emit blockEvents( true );
   switch ( mStorageMode )
   {
     case GetFile:
@@ -287,6 +288,7 @@ void QgsFileWidget::openFileDialog()
     }
     break;
   }
+  emit blockEvents( false );
 
   if ( fileName.isEmpty() && fileNames.isEmpty( ) )
     return;

src/gui/qgsfilewidget.h

@@ -184,6 +184,14 @@ class GUI_EXPORT QgsFileWidget : public QWidget
     //! emitted as soon as the current file or directory is changed
     void fileChanged( const QString & );
 
+    /**
+     * Emitted before and after showing the file dialog.
+     *
+     * \note not available in Python bindings
+     * \since QGIS 3.10
+     */
+    void blockEvents( bool ) SIP_SKIP;
+
   private slots:
     void openFileDialog();
     void textEdited( const QString &path );