[Plib-devel] On First Looking Into Baker's SSG (with apologies to John Keats)

[Fay J. F C. AAC/W. <joh...@eg...>]

MUCH have I travell'd in the realms of gold,  
And many goodly states and kingdoms seen;  
Round many western islands have I been  
Which bards in fealty to Apollo hold.  
Oft of one wide expanse had I been told
That deep-brow'd Homer ruled as his demesne;  
Yet did I never breathe its pure serene  
Till I heard Chapman speak out loud and bold:  
Then felt I like some watcher of the skies  
When a new planet swims into his ken;
Or like stout Cortez when with eagle eyes  
He star'd at the Pacific-and all his men  
Look'd at each other with a wild surmise-  
Silent, upon a peak in Darien. 

--------------------------------------------------

Frankly, I feel that anything I try to write after quoting the above is an
anticlimax.  But here goes.

I printed out the SSG files (except for all the loaders and writers) and
started digging through them over the weekend.  I have a few notes and
questions so far, some trivial and some not trivial.

In the realm of the trivial:
(1) There are several places where tabs are used for indentation instead of
spaces. (ssg.cxx:404,405; ssg.h:357-358, 450)
(2) The variable "sgebug" (ssg.h:43) seems not to be used anywhere.
(3) In "ssgconf.h" on line 35, the word "and" should be "an" ("to an
#undef").
(4) Also in "ssgconf.h" on lines 42-43, I think the instruction to
"un-comment the following line" should be changed to something like "change
the 'undef' on the following like to a 'define'."
(5) In "ssg.h" starting around line 133 there is a rather complex series of
functions that set type data.  The PUI version is considerably more
efficient, but I think I remember there being a discussion about doing SSG
this way so as to avoid a hard limitation on 32 bits.  I would like to
suggest adding a comment to this effect.

In the realm of the not-so-trivial:
(6) From what I gather from "ssg.cxx", we do not have writers for the "dof",
"md2", "strip", "mdl", or "xpl" file formats and we do not have loaders for
the "asc" or "pov" file formats (the latter is commented out entirely).  Do
we need them? Do we want them?
(7) The file "ssgBase.cxx" has a variable "next_unique_id" that starts at 1
and is incremented every time a new "ssgBase" object is created.  The
operation used for this is a postfix "++".  I am told that a prefix "++" is
ever-so-slightly faster because you don't have to save the return value
before incrementing the variable.  Do we want to initialize the variable to
0 (on line 27) and increment it (on line 68) with a prefix "++"?
(8) In the "ssgBase::print" function, do we want to print out the unique ID
as well?  Just asking ... and not pretending to have any knowledge in the
area.
(9) In the "ssgList::removeAllEntities" function (ssgList.cxx:94), the
function removes entity 0 repeatedly until the list is empty.  This is a lot
like unpiling a stack of bricks by removing the bottom one each time; the
"removeEntity" involves a "memmove" call each time.  Why doesn't the
"removeAllEntities" function simply set "total" and "next" to zero?  At the
very least, we can speed up the "memmove" calls by invoking "removeEntity"
with an argument of "total-1" instead of "0".
(10) Do we want to implement PUI-type RTTI in the SSG functions?

Under the heading of real issues:
(11) How would we implement the "puValue" functionality in SSG?  Should we
just add it to "ssgBase" or should it remain separate?  If the latter,
should we use multiple inheritance in the SSG widgets?
(12) How do we handle multiple windows in SSG?  I surmise that we would have
a separate scene-graph tree for each window.  I believe Steve would have
done something like that for PUI except that I put in the multiple-window
support first and didn't ask him.  This time I am asking first.

I daresay there will be many more issues as I continue to dig.

John F. Fay
joh...@eg...