Avoid loss of text in code editors when certain modifiers are pressed

These are triggered when a InputMethod event is sent to the widget.
There's upstream discussion at https://sourceforge.net/p/scintilla/bugs/1913/
and the fix was added to QScintilla version 2.13.3

As the loss of text is an extreme risk, just disable input method
handling in these widgets on affected versions entirely.

Fixes #52459

(cherry picked from commit 8f5476e)

python/gui/auto_generated/codeeditors/qgscodeeditor.sip.in

@@ -223,6 +223,8 @@ it is visible.
 
     virtual void keyPressEvent( QKeyEvent * event );
 
+    virtual bool eventFilter( QObject * watched, QEvent * event );
+
 
     virtual void initializeLexer();
 %Docstring

src/gui/codeeditors/qgscodeeditor.cpp

@@ -104,6 +104,10 @@ QgsCodeEditor::QgsCodeEditor( QWidget *parent, const QString &title, bool foldin
     setSciWidget();
     initializeLexer();
   } );
+
+#if QSCINTILLA_VERSION < 0x020d03
+  installEventFilter( this );
+#endif
 }
 
 // Workaround a bug in QScintilla 2.8.X
@@ -150,6 +154,21 @@ void QgsCodeEditor::keyPressEvent( QKeyEvent *event )
   }
 }
 
+bool QgsCodeEditor::eventFilter( QObject *watched, QEvent *event )
+{
+#if QSCINTILLA_VERSION < 0x020d03
+  if ( watched == this && event->type() == QEvent::InputMethod )
+  {
+    // swallow input method events, which cause loss of selected text.
+    // See https://sourceforge.net/p/scintilla/bugs/1913/ , which was ported to QScintilla
+    // in version 2.13.3
+    return true;
+  }
+#endif
+
+  return QsciScintilla::eventFilter( watched, event );
+}
+
 void QgsCodeEditor::initializeLexer()
 {
 

src/gui/codeeditors/qgscodeeditor.h

@@ -246,6 +246,7 @@ class GUI_EXPORT QgsCodeEditor : public QsciScintilla
 
     void focusOutEvent( QFocusEvent * event ) override;
     void keyPressEvent( QKeyEvent * event ) override;
+    bool eventFilter( QObject * watched, QEvent * event ) override;
 
     /**
      * Called when the dialect specific code lexer needs to be initialized (or reinitialized).