[Scummvm-devel] Contributing to ScummVM with an interpreter for Magnetic Scrolls?

Paul Gilbert paulfgilbert at gmail.com
Wed May 1 05:10:53 CEST 2019


Hi Thomas,

I'm not sure of the status of the Gargoyle Magnetic Scrolls sub-engine, and
I don't currently have any Magnetic Scrolls games handy to test it on. But
unless it's significantly lacking in support for the later games that your
own work adds support for, it'll likely prove easier to work on converting
it, I'm afraid. Since, after all, someone else has already done the work of
hooking it up to Glk as well. So it'll be easier to do minimal work
(relatively speaking) to hook it up to the ScummVM version of the Glk
layer. And then I can keep testing it as I properly objectify everything to
make sure I don't break anything along the way.

Though I'll be unlikely to be spending much time beyond basic polishing up
of the sub-engine afterwards. So based on your experience with the games &
engine involved, there might be opportunities afterwards for you to
contribute if you're interested, and to do pull requests to improve the
functionality of the engine based on your work.

Regards,

Paul.


On Wed, May 1, 2019 at 2:55 AM dettus <dettus at dettus.net> wrote:

> 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.
> 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>
> 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>
>> 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> 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. ;) )
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> Scummvm-devel mailing list
>>>> Scummvm-devel at lists.scummvm.org
>>>> https://lists.scummvm.org/listinfo/scummvm-devel
>>>>
>>>
>>>
>>> --
>>> "Experience is the name every one gives to their mistakes" - Oscar Wilde
>>>
>>
>>
>> --
>> "Experience is the name every one gives to their mistakes" - Oscar Wilde
>> _______________________________________________
>> Scummvm-devel mailing list
>> Scummvm-devel at lists.scummvm.org
>> https://lists.scummvm.org/listinfo/scummvm-devel
>>
>
> _______________________________________________
> Scummvm-devel mailing listScummvm-devel at lists.scummvm.orghttps://lists.scummvm.org/listinfo/scummvm-devel
>
> _______________________________________________
> Scummvm-devel mailing list
> Scummvm-devel at lists.scummvm.org
> https://lists.scummvm.org/listinfo/scummvm-devel
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.scummvm.org/pipermail/scummvm-devel/attachments/20190501/39150a8d/attachment-0001.html>


More information about the Scummvm-devel mailing list