The Athena widgets were developed by MIT's project Athena (they are part of the public domain X Windows release). This widget set was primarily designed as an example and guideline for the use of the X Toolkit and does hence not fulfill all the needs of a CAD-oriented user interface, but it does provide the required basic functionality, it is highly portable, it is available on virtually every modern workstation platform, and it is easy to comprehend. Thus, it is ideally suited as basic object system from which specialized CAD-widgets and extensions can be sub-classed.
Figure 3.3: The class tree of the widgets used by VISTA.
The VISTA widgets are shaded, the
Intrinsics and Athena
widgets used for sub-classing are blank.
The VISTA widgets are sub-classed from either
X Toolkit Intrinsics or Athena
widgets (Figure 3.3). The Canvas,
PED, PedGraph, and Ruler are parts of the
interactive PIF Editor (PED),
the IntValue, RealValue, Quantity, FileSel,
and String widgets allow the specification of
integer numbers, real numbers, physical quantities (with units),
files, and string values, respectively, and the
SVGraph widget displays simple vector graphics
plots. The VpiGraph is a planned
extension
for visual programming.
Figure 3.4 shows a test application that contains all of the simple
widget sub-classes used within VISTA.
Figure 3.4: Collection of Athena and VISTA widgets