[Scummvm-devel] Contributing to ScummVM with an interpreter for Magnetic Scrolls?
dettus
dettus at dettus.net
Tue Apr 30 18:55:11 CEST 2019
Hello.
I must admit that I have not heard about Gargoyle or GLK before.
Judging from the github repository, the Gargoyle engine for Magnetic
Scrolls is using the original magnetic interpreter from Niclas Karlson.
What he did was, as far as I know, reverse-engineer the C64 ports of the
Magnetic Scrolls games in a painstaking process to make them run on DOS.
What I did was starting from scratch and using his code as a reference.
His code is probably more settled than mine. Plus, I'd hate to step on
somebody's toes who has already invested copious amounts of time and
energy into a project, so if you prefer to use his code: Please, please
do so!
What I can offer you is an engine using a more modern coding style. Even
though it is C, I am sure that it can be integrated easily with C++
projects. I have worked with projects that use both languages and I am
experienced in designing APIs for that.
Thus far, I have the following function pointers for callbacks:
typedef int (*cbLineAOutputChar)(void* context,char c,unsigned char
controlD2,unsigned char flag_headline);
typedef int (*cbLineAOutputString)(void* context,char* string,unsigned
char controlD2,unsigned char flag_headline);
typedef int (*cbLineAInputString)(void* context,int* len,char* string);
typedef int (*cbLineADrawPicture)(void* context,tPicture* picture,int mode);
typedef int (*cbLineASaveGame)(void* context,char* filename,void*
ptr,int len);
typedef int (*cbLineALoadGame)(void* context,char* filename,void*
ptr,int len);
As well as those API functions:
// configuration functions
int lineA_getsize(int* size);
int lineA_init(void* hLineA,void* pSharedMem,int *sharedmemsize,void*
pMag,int magsize,void* pGfx,int gfxsize);
int lineA_getVersion(void* hLineA,int* version);
int lineA_setCBoutputChar(void* hLineA,cbLineAOutputChar pCB,void *context);
int lineA_setCBoutputString(void* hLineA,cbLineAOutputString pCB,void*
context);
int lineA_setCBinputString(void* hLineA,cbLineAInputString pCB,void*
context);
int lineA_setCBDrawPicture(void* hLineA,cbLineADrawPicture pCB,void*
context);
int lineA_setCBSaveGame(void* hLineA,cbLineASaveGame pCB,void* context);
int lineA_setCBLoadGame(void* hLineA,cbLineALoadGame pCB,void* context);
You typically initialize the engine with pointers to the game binaries,
set the function pointers, and let it run. When it reaches a point where
an input is required, the engine generates a callback and pauses until
the callback returns.
Regarding pictues: They are also being rendered internally, and another
callback is triggered. An upper layer must draw it in whatever way it
deems appropriate. So, it does not really care where it sits, or if it
will even be displayed. The data format itself is very basic, almost .xpm.
typedef struct _tPicture
{
unsigned int palette[16];
int height;
int width;
char pixels[65536];
} tPicture;
I am sure I can design an extra function for animations, such as this:
typedef int (*cbLineADrawAnimation)(void* context,tPicture* frames[],int
mode,int framenum,int delay);
Please let me know if this is of interested to you.
Thomas
On 4/30/19 2:20 AM, Paul Gilbert wrote:
> Hi guys,
>
> Thanks for the excellent summary of the current status, Filippos. As
> he said, I'm currently in the middle of working my way through
> converting all the Gargoyle engines to ScummVM, cleaning them up and
> making them conform to our coding requirements, as well as making them
> proper C++ classes. If you do decide to work on the Gargoyle
> sub-engine, please let me know.. I'll hold off working on it until
> after I've converted the remaining sub-engines. That'll give you
> plenty of time.. the TADS & Hugo sub-engines are big enough that
> that'll likely take me a while to finish converting :).
>
> If you have any questions about the Glk engine specifically, feel free
> to drop me a line. There's also the technical forums at
> intfiction.org <http://intfiction.org>. Though my schedule is a bit
> packed for the next few weeks, so if you do email, I may take a bit to
> get back to you.
>
> As far as music and animation goes, music at least should be easy, so
> long as it's a standard format ScummVM understands. Currently the
> engine supports raw sound, wav files, aiff, and mp3. As for graphics,
> that's somewhat straightforward as well, as long as the graphics can
> be segmented into completely separate windows than the text, and it
> looks like the Magnetic Scroll games do.. when you create windows in
> Glk, you can specify what portion of the screen each will use (for
> text vs graphics). I've had a lot of trouble with the Frotz
> sub-engine, but only because graphics and text can intermingle in the
> same windows, which Glk doesn't allow.
>
> Regards,
>
> Paul Gilbert (aka DreamMaster).
>
>
>
>
>
> On Mon, Apr 29, 2019 at 7:18 PM Filippos Karapetis <bluegr at gmail.com
> <mailto:bluegr at gmail.com>> wrote:
>
> Sorry, forgot to say that the glk engine in ScummVM can be found
> here:
> https://github.com/scummvm/scummvm/tree/master/engines/glk
>
> There are currently subengines for the alan2, frotz, glulxe,
> magnetic, scott, and tads interpreters, in various stages of
> development. dreammaster is mainly working on these. You can also
> find information about the glk engine in our wiki:
> https://wiki.scummvm.org/index.php?title=ScummGlk
>
> Regards
> Filippos Karapetis
>
> On Mon, Apr 29, 2019 at 12:14 PM Filippos Karapetis
> <bluegr at gmail.com <mailto:bluegr at gmail.com>> wrote:
>
> Hello, and glad to hear about your interest in ScummVM, and
> your work on the Magnetic Scrolls games!
>
> It's great that you are working on this. Bear in mind, though,
> that there has been extensive work on the Magnetic Scrolls
> games, which has been integrated into the Gargoyle interpreter:
> http://ccxvii.net/gargoyle/
>
> Gargoyle is being integrated as a subengine into ScummVM, in
> the glk engine. The glk engine is a port of the Gargoyle
> engine into ScummVM. There's an extensive wiki for Gargoyle, here:
> http://ifwiki.org/index.php/Gargoyle
>
> So, my advice would be to make your engine part of the glk
> engine, and base your work on the already working Magnetic
> Scrolls interpreter from the Gargoyle engine. The interpreter
> is open source, and can be found here:
> https://github.com/garglk/garglk/tree/master/terps/magnetic
>
> The list of supported Magnetic Scrolls games can be found here:
> https://github.com/garglk/garglk/blob/master/terps/magnetic/Generic/games.txt
>
> And there's an archive about interactive fiction games, where
> a lot of resources about the Magnetic Scrolls games can be
> found, here:
> http://www.ifarchive.org/indexes/if-archive/magnetic-scrolls/
>
> Thanks for your interest in these games! It would be great to
> see your work on them :)
>
> Regards
> Filippos Karapetis
>
>
> On Mon, Apr 29, 2019 at 10:08 AM dettus <dettus at dettus.net
> <mailto:dettus at dettus.net>> wrote:
>
> Hello.
>
>
> My name is Thomas, I am a big fan of ScummVM.
>
> Currently, I am in the process of writing an interpreter
> for classic
> text adventures from Magnetic Scrolls, such as "The Pawn"
> or "The Guild
> Of Thieves".
>
> Even though I am not saying that it SHOULD be integrated
> into ScummVM, I
> would like to think that it COULD. It is WAY to early to
> really start
> integrating it, but I like to be prepared.
>
>
>
> So, the reason why I am writing this mail is because I
> would be
> interested as on how I would have to design my code to
> make it possible.
> Currently, my interpreter needs a couple of hooks into any
> form of GUI:
>
> - Initialization, where pointers to the original binaries
> are being provided
>
> - Callbacks for textual input (strings)
> - Callbacks for textual output (strings)
> - Callbacks for textual output (characters)
> - Callbacks for drawing a picture (XPM)
>
> My code is purely C, so callbacks I am using function
> pointers. Said
> functions are, at the moment, doing nothing more than just
> a simple
> printf() and fgets(). The games I can play so far are "The
> Pawn", "The
> Guild of Thieves" and "Jinxter". HOWEVER, later games,
> such as
> "Corruption", "Myth", "Fish!" and "Wonderland" added
> features such as
> animation and music.
>
> SO MY QUESTION is this: How would I best design the
> callbacks for
> animation and music in way so that it MIGHT be
> integratable into ScummVM?
>
>
>
> Dettus
>
>
>
> P.S.: My interpreter is available at
> http://www.dettus.net/dMagnetic.
>
> (Hopefully this link, and the fact that this is my first
> email will not
> make this spam. ;) )
>
>
>
>
>
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>
>
> --
> "Experience is the name every one gives to their mistakes" -
> Oscar Wilde
>
>
>
> --
> "Experience is the name every one gives to their mistakes" - Oscar
> Wilde
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