[Scummvm-devel] HE games support strategy

[Eugene Sandulenko]

Hi all,

especially Kirben and khalek.

There've been rapid progress on latter HE games support, nicknamed HE
v7.0+. Here I would like to present our strategy. It was hammered
mainly by me an Kirben, but is good to be archived/discussed and
presented to khalek and whoever who wants to help us with this giantic
task.

The most difficult non-RE question in these titles is exact game
position in SPUTM engine evolution line. There are some about 50+
titles, some of which are released with different generation
engines. So, it is good if we will continue our current route, i.e. go
from minor versions to major.

What we saw, the mother of all HE games is DOS version of Putt-Putt
Parade game. It is went so less from original SCUMM v6, so it's engine
version did not get any HE extensions or changes, only file naming
scheme was altered and maybe some minor thing like this. After this
version engine was extended almost for each game, but there are still
clear classes and games which share same engine. We decided to go with
two-digits numbering scheme a the moment, and that may not reflect
original HE versioning which we see in some of their executables. That
is because often version wasn't changed at all while engine was
changed enough. A good example of this is 7.0.0 version of Freddi Fish
1, which is 640x480 and doesn't run with current ScummVM.

In scumm_settings table in scumm.c there is a field named heversion,
and its value is porpagated to ScummEngine object variable
_heversion. If that game has specific but minor changes, which do not
deserve bumping _heversion, then new GID should be created and
assigned to it. But since most engines inherit their predecessor's
changes it is best to use _heversion rather creating 50 GIDs for each
game.

So now on how to determine engine version.

Present time there are four important reference tables we all have to
use to determine where this or that game is positioned, thus knowing
exact target to aim. They are no way are final and may be inaccurate
even in current content.

  http://members.optusnet.com.au/scummvm/misc/humongous.txt

  This table is more or less informational. It contains some strings
from executables, where we see when this game was released and which
interpretator version HE attached to it.  What I would like to add
there is a field with nicks of those who has this particular game,
size and date of executable, and of course, convert it to HTML.


  http://members.optusnet.com.au/scummvm/he_chart.html

  In this tables games are sorted in what we believe chronological
order. Game resolution was determined by test run, so it is
accurate. VARS type was determined by Kirben by means of quick glimpse
(he knows the trick), and currently it has 2 kinds of tables. scumm6
is an unchanged SCUMM vars table, and sputm7.2 is HE's custom vars
table. But more deep research may show up more differences among
those. 


  http://members.optusnet.com.au/scummvm/misc/chart.html

  This is a huge table of opcodes. It contains just few games. It is
main source of information which games share same engine and where in
time they should be positioned. What I saw in the engines, they tend
to grow with each new version, so having them be sorted by function
addresses lead us to more or less accurate evolution picture.

  http://khalek.tolmie.net/scumm/he-md5s.txt

  This table is new, but I would like to use it more, by connecting it
with first game. I.e. we will see who has which game and so we may be
sure we work on _same_ engine for some particular title. Right now it
has games owned by khalek, but we should consider checking our
collections, fill spots and add our nicks on titles we own.


First you check either this game is in huge chart.html. If it's not,
you should produce appropriate column for it. If you can't do it in
more that 10 minutes, send request to me, that's quick operation
here.

In general we should go from left to right in this table. Right now
we're at puttmoon.w32 position. We call that version 7.0. See
he_chart.html table. So if your game is not right next to it (and you
don't have predecessing games), this should be discussed as it may or
may not make all development clobberish.

Then after you determined which game you will be working on, you need
to determine how big changes are. You have three options: another GID,
minor heversion change or major heversion.

That is our vision of the subject, your comments are welcome.


Eugene