How to use

getClosestWidgetLineForModelLine

method

in

org.eclipse.jface.text.TextViewer

@Override
public void setTopIndex(int index) {
  if (fTextWidget != null) {
    int widgetLine= modelLine2WidgetLine(index);
    if (widgetLine == -1)
      widgetLine= getClosestWidgetLineForModelLine(index);
    if (widgetLine > -1) {
      fTextWidget.setTopIndex(widgetLine);
        updateViewportListeners(INTERNAL);
    }
  }
}

@Override
public void setTopIndex(int index) {
  if (fTextWidget != null) {
    int widgetLine= modelLine2WidgetLine(index);
    if (widgetLine == -1)
      widgetLine= getClosestWidgetLineForModelLine(index);
    if (widgetLine > -1) {
      fTextWidget.setTopIndex(widgetLine);
        updateViewportListeners(INTERNAL);
    }
  }
}

/**
 * Updates the viewport, trying to keep the
 * {@linkplain StyledText#getLinePixel(int) line pixel} of the caret line stable. If the
 * selection has been updated while in redraw(false) mode, the new selection is revealed.
 */
private void updateViewport() {
  if (fSelectionSet) {
    revealRange(fSelection.getOffset(), fSelection.getLength());
  } else if (fStableLine != null) {
    int stableLine;
    try {
      stableLine= fUpdaterDocument.getLineOfOffset(fStableLine.getOffset());
    } catch (BadLocationException x) {
      // ignore and return silently
      return;
    }
    int stableWidgetLine= getClosestWidgetLineForModelLine(stableLine);
    if (stableWidgetLine == -1)
      return;
    int linePixel= getTextWidget().getLinePixel(stableWidgetLine);
    int delta= fStablePixel - linePixel;
    int topPixel= getTextWidget().getTopPixel();
    getTextWidget().setTopPixel(topPixel - delta);
  }
}

/**
 * Updates the viewport, trying to keep the
 * {@linkplain StyledText#getLinePixel(int) line pixel} of the caret line stable. If the
 * selection has been updated while in redraw(false) mode, the new selection is revealed.
 */
private void updateViewport() {
  if (fSelectionSet) {
    revealRange(fSelection.getOffset(), fSelection.getLength());
  } else if (fStableLine != null) {
    int stableLine;
    try {
      stableLine= fUpdaterDocument.getLineOfOffset(fStableLine.getOffset());
    } catch (BadLocationException x) {
      // ignore and return silently
      return;
    }
    int stableWidgetLine= getClosestWidgetLineForModelLine(stableLine);
    if (stableWidgetLine == -1)
      return;
    int linePixel= getTextWidget().getLinePixel(stableWidgetLine);
    int delta= fStablePixel - linePixel;
    int topPixel= getTextWidget().getTopPixel();
    getTextWidget().setTopPixel(topPixel - delta);
  }
}