Script lua

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Script_lua is a basic example plugin. This wiki page is intended as a walkthrough of the code in order to help you better understand the SDK.

This plugin serves as a Lua script interpreter.

Code Walkthrough

The code structure for this plugin is somewhat atypical. In our header we declare a variety of functions which we define in the related cpp. However, our main class, the one from which we will build our server, is in another cpp entirely and has a utility that takes the functions that we defined and adds them to the aforementioned class.

Declarations

lxlua.h

This is a struct that defines certain objects and constants that will be used by the plugin.

typedef struct st_IntrInstance {
       ILxScriptID	 script;		// Script being executed.
       ILxMonitorID	 monitor;		// Progress monitor used by lxmon??? functions.
       int		 askedForMonitor;	// True if we asked for the monitor.
       LxResult	 rc;			// Result code from the most recently executed/queried command.
       int		 tracing;		// 1 if tracing is active, 0 if inactive.
       int		 execFlags;		// Flags provided by the caller of Run() and used for command execution.

       CLxUser_LogEntry log;			// For logging data

       int		 queryAnglesAsDegrees;	// True if queried angles should be returned in degrees instead of radians.
} IntrInstance;

Declaration of functions that will be used by the plugin.

extern "C"  int   l_lxout(lua_State *L);
extern "C"  int   l_lx(lua_State *L);
extern "C"  int   l_lxq(lua_State *L);
extern "C"  int   l_lxqt(lua_State *L);
extern "C"  int   l_lxeval(lua_State *L);
extern "C"  int   l_lxok(lua_State *L);
extern "C"  int   l_lxres(lua_State *L);
extern "C"  int   l_lxtrace(lua_State *L);
extern "C"  int   l_lxoption(lua_State *L);
extern "C"  int   l_lxsetOption(lua_State *L);
extern "C"  int   l_lxmonInit(lua_State *L);
extern "C"  int   l_lxmonStep(lua_State *L);

lxlua.cpp

Here we declare a variety of scripts and services that will be used below. "extern" indicates that the objects inside have already been defined elsewhere so the compiler won't complain.

extern "C" {

ILxScriptSysServiceID		 scriptSrv;			/* Script system service; common to all instances                */
ILxStdDialogServiceID		 dlgSrv;			/* Standard dialog service; common to all instances              */
IntrInstance			 intrStack[ MAX_STACK ];	/* Interpreter stack; allows scripts to execute other scripts    */
int				 intrTop        = -1;		/* The current script being executed as an index into interStack */
IntrInstance			*intrCur        = NULL;		/* The same as &intrStack[ intrTop ], or NULL if intrTop is -1   */

}

Class Declarations

intrlua.cpp

This class is intended to take a lua script and interpret it, so we need it to be a modified text editor. To this end, we inherit from CLxImpl_TextScriptInterpreter.

The first two functions of note inside the class are those with the tsi prefix, indicating that they are redeclarations of virtual functions inside the CLxImpl_TextScriptInterpreter class.The ValidateFileType makes sure that the file we are being passed is of the correct format. The Run function takes the file we have been given and interprets it line by line.

The Init starts up our interpreter. However, on top of that it also adds all the functions that we declared in the header file and then defined in a separate cpp. These functions handle logging, options, and the progress bar. There is also a sort of master function which performs all the queries or executes. The Kill function simply shuts down our interpreter.

class CLuaInterpreter : public CLxImpl_TextScriptInterpreter
{
       CLxUser_LogService	logSvc;
       CLxUser_CommandService	cmdSvc;
       CLxUser_ValueService	valueSvc;

   public:
       virtual			~CLuaInterpreter () {}

       virtual LxResult	 tsi_ValidateFileType (
                                       ILxUnknownID	 scriptObj,
                                       const char	*firstLine) LXx_OVERRIDE;
       virtual LxResult	 tsi_Run (
                                       ILxUnknownID	 scriptObj,
                                       int		 execFlags,
                                       const char	*args,
                                       ILxUnknownID	 messObj) LXx_OVERRIDE;
        
       void			 Init ();
       void			 Kill ();
 
       static LXtTagInfoDesc	 descInfo[];

   private:
       lua_State		*L;
};

Server Tags

Servers tags are examined when the server is initialized, and give information about the server. We set the tags in this case by taking descinfo[] arrays and associating the relevant data with the corresponding flags.

The tags here indicate that the server we will be exporting has the name "Lua Scripts" and deals with files of the type .lua.

LXtTagInfoDesc	 CLuaInterpreter::descInfo[] = {
       { LXsSRV_USERNAME,	"Lua Scripts"	},
       { LXsLOD_DOSPATTERN,	"*.lua"		},
       { 0 }
};

The tags here indicate that CLuaInterpreter has the name Lua Scripts and takes files with the .lua extension.

Initialize

Intialize is called when we add the plugin to modo, and is the utility that exports the server. The LXx_ADD_SERVER method is simply a wrapper that is identical to normal method of adding a server, with the arguments being (interface_to_be_added, class_you_depend_on, server_name).

This initialize function exports one server of the type TextScriptInterpreter that is dependent on the class CLuaInterpreter and has the name lua.

       void
initialize ()
{
       LXx_ADD_SERVER (TextScriptInterpreter, CLuaInterpreter, "lua");
} 

Implementations

lxlua.cpp

Add a string to a parent log, possibly returning a log entry for sub-entries

       static void 
AddLogStringEntry (
       CLxLoc_LogEntry		&parent,
       const char		*s,
       LxResult		 code,
       int			 persist,
       CLxLoc_LogEntry		&entry)
{
       ...
}

Adding a log entry to a parent, for clients with no need for the entry.

void
AddLogString (
       CLxLoc_LogEntry		&parent,
       const char		*s,
       LxResult		 code,
       int			 persist)
{ 
       ...
}

Logging for clients with no need for the entry.

       void
LogString (
       const char		*s,
       LxResult		 code,
       int			 persist)
{
       ...
}

lxout: Output a string to the log

       int
l_lxout(lua_State *L)
{
       ...
}

Internal function to perform queries and executions

#define LXEVALMODEf_QUERY	1						// Query only; fail if no query is marked
#define LXEVALMODEf_EXECUTE	2						// Execute only; fail if a query is marked
#define LXEVALMODEf_EITHER	(LXEVALMODEf_QUERY | LXEVALMODEf_EXECUTE) 	// Query or execute, whatever works

       LxResult
lxeval(lua_State *L, int mode)
{
       ...
}

At some point in the future, lxq() needs to use the raw string conversion feature to ensure that the values that are queried are the same kinds of values that get passed to commands.

       int
l_lxq(lua_State *L)
{
       ...
}

lxqt(): Query a toggle command's toggle argument. Returns the query state on success (1 or 0), or 0 on failure.

       int
l_lxqt(lua_State *L)
{
       ...
}

Return true if the last command executed/queried successfully.

       int
l_lxok(lua_State *L)
{
       ...
}

Return the LxResult code of the last command executed or quieried.

       int
l_lxres(lua_State *L)
{
      ...
}

When activated, lx() and lxq() data is output to the event log. If no args are passed in, this returns if tracing is active or not.

       int
l_lxtrace(lua_State *L)
{ 
       ...
}

Get the state of an option.

       int
l_lxoption(lua_State *L)
{
      ...
}

Get the state of an option.

       int
l_lxsetOption(lua_State *L)
{
       ...
}

Initialize the progress bar. Initialize the progress bar with n total steps. Returns 0 on error.

       int
l_lxmonInit(lua_State *L)
{
      ...
} 

Step the progress bar. Increment the progress bar by n steps, or 1 step if no steps are provided. This always returns true unless the user aborts, in which case it returns false.

       int
l_lxmonStep(lua_State *L)
{
      ...
}

verifies that the file passed in is of the lua type.

       LxResult
CLuaInterpreter::tsi_ValidateFileType (
       ILxUnknownID		  scriptObj,
       const char		 *firstLine)
{
       ...
}	

intrlua.cpp

adds all of the functions just implemented in lxlua.cpp to CLuaInterpreter

       void
CLuaInterpreter::Init()
{
       ...
}

performs most of the work, is the function that actually interprets the file.

       LxResult
CLuaInterpreter::tsi_Run (
       ILxUnknownID		 scriptObj,
       int			 execFlags,
       const char		*args,
       ILxUnknownID		 messObj )
{
       ...
}  

This function cleans up.

       void
CLuaInterpreter::Kill()
{
       ...

}