🚀 go-pugleaf

In article <zen.721007140@texas>, you write:

> In Unidraw, there are pre-defined graphic shapes, such as rectangular
> and so on.  Where are they defined?  How can I define a new shape?

Unidraw defines such shapes both at the structured graphics level (in
include/Unidraw/Graphic) and at the component level
(include/Unidraw/Components).  The structured graphics classes rely on
Painter's immediated mode interface to draw themselves, and the
components rely on structured graphics to define their appearance.

To define a new structured graphic, you basically subclass from Graphic
(or a subclass thereof) and redefine its draw and getExtent methods.
You must also redefine the graphics state setting and getting operations
(e.g., SetBrush) for graphics state that your subclass cares about.  If
you want fine-grain hit detection, then you must also redefine the
contains and intersects operations.  The Line class (in
include/Unidraw/Graphic/lines.h) provides a good example of what you
must do.

To define a new graphical component, you must

    1. Define a subject by subclassing from GraphicComp (or a subclass
       thereof).

    2. Define a view by subclassing from GraphicView (or a subclass
       thereof).

    3. Define class identifiers for the new component subject and view
       (see include/Unidraw/classes.h for an example).

    4. Define a Creator subclass that can create instances of the new
       component subject and view given their class identifiers (see
       lib/Unidraw/creator.c for an example).

For more details, see the definition of LineComp and LineView in
include/Unidraw/Components/lines.h and lib/Unidraw/lines.h.

--
John Vlissides / IBM T.J. Watson Research / vlis@watson.ibm.com