void recalcEditorDimensions() {
    EditorImpl.MyScrollBar scrollBar = myEditor.getVerticalScrollBar();
    int scrollBarHeight = Math.max(0, scrollBar.getSize().height);

    myEditorScrollbarTop = scrollBar.getDecScrollButtonHeight()/* + 1*/;
    assert myEditorScrollbarTop>=0;
    int editorScrollbarBottom = scrollBar.getIncScrollButtonHeight();
    myEditorTargetHeight = scrollBarHeight - myEditorScrollbarTop - editorScrollbarBottom;
    myEditorSourceHeight = myEditor.getPreferredHeight();

    dimensionsAreValid = scrollBarHeight != 0;
  }
void recalcEditorDimensions()