Editor: fix selecting multiple block selections with mouse

Change-Id: I5b46adbf38358d1396ee7120558648b1375e4047
Reviewed-by: Marcus Tillmanns <marcus.tillmanns@qt.io>
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/libs/utils/multitextcursor.cpp

@@ -50,6 +50,12 @@ void MultiTextCursor::addCursor(const QTextCursor &cursor)
     mergeCursors();
 }
 
+void MultiTextCursor::addCursors(const QList<QTextCursor> &cursors)
+{
+    m_cursors.append(cursors);
+    mergeCursors();
+}
+
 void MultiTextCursor::setCursors(const QList<QTextCursor> &cursors)
 {
     m_cursors = cursors;

src/libs/utils/multitextcursor.h

@@ -57,6 +57,7 @@ public:
     /// the \param cursor that is appended by added by \brief addCursor
     /// will be interpreted as the new main cursor
     void addCursor(const QTextCursor &cursor);
+    void addCursors(const QList<QTextCursor> &cursors);
     /// convenience function that removes the old main cursor and appends
     /// \param cursor as the new main cursor
     void replaceMainCursor(const QTextCursor &cursor);

src/plugins/texteditor/texteditor.cpp

@@ -5335,7 +5335,7 @@ void TextEditorWidget::mouseMoveEvent(QMouseEvent *e)
                                                                         anchorCursor.blockNumber(),
                                                                         anchorColumn};
 
-        cursor.setCursors(d->generateCursorsForBlockSelection(blockSelection));
+        cursor.addCursors(d->generateCursorsForBlockSelection(blockSelection));
         if (!cursor.isNull())
             setMultiTextCursor(cursor);
     } else {