Creates the content of the popup window.
Implementors will usually take over
Composite#getBackground() and
Composite#getForeground() from parent
.
Implementors must either use the dialog font or override
#computeSizeConstraints(int,int).
Implementors are expected to consider
#isResizable(): If true
, they
should show scrollbars if their content may exceed the size of the information control. If
false
, they should never show scrollbars.
The given parent
comes with a
FillLayout. Subclasses may set a different
layout.