QTextCursor selection forward and backward problem only on linux

I have subclass QGraphicsItem to write a Layer text editor... xhtml editor
Subversion:
http://fop-miniscribus.googlecode.co...phicsViewEdit/

Now i have problem on Linux..
this MouseMoveEvent run perfect on Window XP qt4.4 and QTextCursor select correct text
forward and backward ...

Why on linux (ubuntu) qt4.4 it select the full line and can not select only one or two Character?

Code:

/* subversion /include/mounttextprivate.cpp */
/* StartSelectionMouse =  mouse position (QTextCursor) from MousePressEvent  */
 
void TextWriter::tmouseMoveEvent(QEvent *e, Qt::MouseButton button, const QPointF &pos)
{
	///////////qDebug() << "### mouseMoveEvent in ";
	const int cursorPos = _d->documentLayout()->hitTest(pos,Qt::ExactHit) + 1;
	const int cursornow = cursorPos - 1;
	/* if drag move mime make and return !!! */
	if (C_cursor.hasSelection() && DragFill) {
		cursortime = false;
		repaintCursor();
		return;
	}
	const int cursorPosFozze = _d->documentLayout()->hitTest(pos,Qt::FuzzyHit);
	const int stopat = qMax(StartSelectionMouse,cursorPos); 
	const int startat = qMin(StartSelectionMouse,cursorPos);
	  ////////////qDebug() << "### start/stop cell position " << StartSelectionMouse << cursorPos << cursorPosFozze;
	  if (StartSelectionMouse != -1 && cursorPos > 0 && !C_cursor.currentTable()) {
			if (StartSelectionMouse != cursorPos) {
	       /////////setBlinkingCursorEnabled(false);
				/* selection tracer */
			  cursorIsFocusIndicator = true;
				 if (stopat == cursorPos) {
					   /* cursor selection mode start>>>>>>>>>>>>>>>>>stop */
						 C_cursor.setPosition(StartSelectionMouse);
						 for (int i = StartSelectionMouse; i < cursorPos; ++i) {
						 C_cursor.movePosition(QTextCursor::NextCharacter, QTextCursor::KeepAnchor);
						 }
						 cursor_position = stopat;
			   } else {
					   /* cursor selection mode stop<<<<<<<<start */
					   C_cursor.setPosition(stopat);
					   const int diffs = stopat - cursornow;
					   /////////qDebug() << "### diffs " << diffs << "," << cursornow << "," << stopat;
					    for (int i = 0; i < diffs; ++i) {
								C_cursor.movePosition(QTextCursor::PreviousCharacter, QTextCursor::KeepAnchor);
							}
					  return;
				 }
				 repaintCursor();
			}
		} 
 
		 if ( C_cursor.currentTable() ) {
			QTextTable *table = C_cursor.currentTable();
			QTextTableCell firstcell = OnPosition(StartSelectionMouse);
			QTextTableCell lastcell = OnPosition(cursorPosFozze);
			if ( firstcell.isValid() && lastcell.isValid() ) {
			int fcellrow = firstcell.row();
			int fcellcool = firstcell.column();
			int numRows = qBound(1,lastcell.row() - fcellrow,table->rows());
			int numColumns = qBound(1,lastcell.column() - fcellcool,table->columns());
			///////qDebug() << "### nnrow / nncool " << numRows << numColumns;
			C_cursor.selectedTableCells(&fcellrow,&numRows,&fcellcool,&numColumns);
			C_cursor.setPosition(firstcell.firstPosition());
			C_cursor.setPosition(lastcell.lastPosition(), QTextCursor::KeepAnchor);
			cursor_position = stopat;
			setBlinkingCursorEnabled(false);
			QRectF tablerect = _d->documentLayout()->frameBoundingRect(table);
			emit updateRequest(tablerect);
			return;
			}
		}
}