(In reply to Ralf Habacker from comment #8)

> Created attachment 88069 [details]
> Hiding problems with UML2 interface ball an socket notation
>
> There are additional hiding problems in this diagram

Thanks for the test case.  Here is my attempt at fixing; please confirm.

umbrello/widgets/widget_utils.{h,cpp} function closestPoints()
- New function determines the approximate closest points of two polygons.

umbrello/widgets/associationwidget.cpp function calculateEndingPoints()
- In case (size < 2), pass QPainterPath::toFillPolygon() converted shape()
  of pWidgetA and pWidgetB into call of Widget_Utils::closestPoints().
  Pass components p1() and p2() of returned QLine into call of
  m_associationLine->setEndPoints().

umbrello/widgets/classifierwidget.{h,cpp}
- New member m_pInterfaceName of type FloatingTextWidget holds the name in
  case of interface drawn as circle.
- Reimplement UMLWidget functions onWidget() and widgetWithID() to include
  consideration of m_pInterfaceName.

umbrello/widgets/classifierwidget.cpp
- In function shape() case
    (classifier()->isInterface() && visualProperty(DrawAsCircle)),
  add only the ellipse of the current rect() to path.
- In function drawAsCircle(),
  - In case (m_Assocs.size() > 1) fix Y value of requireArc;
  - Remove painting of name underneath circle, this is now delegated to
    the FloatingTextWidget m_pInterfaceName.
- In function calculateAsCircleSize() remove coding of name underneath
  circle, this is now delegated to the FloatingTextWidget m_pInterfaceName.
- In function setDrawAsCircle(),
  - In case drawAsCircle add allocation of m_pInterfaceName and set up its
    geometry;
  - Choose same center point between circular and rectangular display so
    that on toggling argument the widget changes shape but not position.
- In function changeToClass() ensure that visualProperty(DrawAsCircle) is
  false.
- In functions {loadFrom,saveTo}XMI add loading/saving of m_pInterfaceName
  as child <floatingtext>.

umbrello/widgets/floatingtextwidget.cpp function onWidget()
- Consider case pw->baseType() == wt_Interface with
  ClassifierWidget::getDrawAsCircle() returning true in on-widget test.
- Clearly separate handling of parent-widget relative (isWidgetChild=true)
  from absolute (isWidgetChild=false) coordinates.

umbrello/version.h
- Increment XMI_FILE_VERSION due to added <floatingtext> in
  <interfacewidget drawascircle="1">

CCBUG:128351