XCMD Limitations

[Richard Gaskin]

Ben Rubinstein wrote:
 
> I've negotiated an allocation of a limited time to demonstrate that the
> system can succesfully be transitioned to MC/Rev; otherwise it's going to go
> elsewhere.  I can recode the other externals in native MetaTalk, and if we
> get to continue down this path I will, for speed and cleanliness; but if I
> can't get the whole thing working quite quickly, that path will be capped.

If MC can't run a particular XCMD/XFCN, chances are no other program but
HyperCard itself will be able to either.

With an admittedly limited understanding of the project, it would seem that
even in the the worst-case scenario -- if they need to recode the external
-- they'd still save money using MC (assuming relying on HC isn't an
option).

What alternatives would be more cost-effective?

> Obviously Scott knows which callbacks he implemented.  Is there a published
> list anywhere?

Wouln't the list you need be present in the headers files ("XCmdGlue.h",
etc.) in the external example?

Here's a partial list from XCmdGlue.h:

extern void SendCardMessage();
extern void SendMCMessage();
extern char *EvalExpr();
extern char *GetGlobal();
extern void SetGlobal();
extern char *GetVariable();
extern void SetVariable();
extern void GetVariableEx();
extern void SetVariableEx();
extern void GetArray();
extern void SetArray();
extern char *GetFieldByName();
extern char *GetFieldByNum();
extern char *GetFieldById();
extern void SetFieldByName();
extern void SetFieldByNum();
extern void SetFieldById();
extern void ShowImageByName();
extern void ShowImageByNum();
extern void ShowImageById();

As a general rule, the HyperCard 1.x suite is widely supported by programs
that support XCMDs, but any callbacks specific to the HyperCard 2.x suite
are supported by none by HC itself.

Thus far I've managed to avoid writing a single external since I started
working with MC in '97 (I hired out the only one I couldn't make in native
MetaTalk), so my knowledge of how MC works with externals is very limited.
Hopefully somone with experience with this can take a moment to fill in the
details... 
 
-- 
 Richard Gaskin 
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