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SLContext.h

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/*
    File:           SLContext.h

    Function:       State machine for rendering a scene. You can add attributes
                    to the context, and also push & pop the current context.
                    
    Author(s):      Andrew Willmott

    Copyright:      (c) 1995-2000, Andrew Willmott
 */

#ifndef __SLContext__
#define __SLContext__


#include "cl/NArray.h"
#include <iostream.h>


#define SC_GET(X) ((sc ## X *) context->Get(a ## X))
// shorthand for fetch & cast: assumes existance of a local variable
// context pointing to the current context.


// --- Attribute types & definition -------------------------------------------

// We don't store the attributes themselves. Instead we store pointers
// to attributes that reside in the scene tree.
// We also define daemons that can be installed to process attributes as they
// are encountered.

typedef Int             AttrType;
typedef Void            *AttrPtr;

class AttrDaemon 
{
    public:
    
    virtual Void            Set(AttrPtr attrPtr) = 0;
    virtual AttrPtr         Get() = 0;
    virtual Void            Save() = 0;
    virtual Void            Restore() = 0;
};

class AttrRec
{
public:
    union
    {
        AttrPtr         data;
        AttrDaemon      *daemon;
    };
    UInt16              level;  // level at which it was last set 
};

class AttrStackRec
{
public:
    AttrRec     attrRec;
    AttrType    attrType;
};

ostream &operator << (ostream &s, const AttrRec &ar);
ostream &operator << (ostream &s, const AttrStackRec &asr);

typedef NArray<AttrRec> AttrList;
typedef NArray<AttrStackRec> AttrStackList;


// --- The SLContext class ----------------------------------------------------


class SLContext
{
public:
    SLContext(Int maxAttributes);

    AttrPtr             Get(AttrType attrType);
    Void                Set(AttrType attrType, AttrPtr attrPtr);
    Void                SetDaemon(AttrType attrType, AttrDaemon *daemon);
    
    Bool                IsCurrent(AttrType attrType);
    
    Void                Push();     
    Void                Pop();      
    Void                Clear();    

protected:  
    AttrList        attributeList;
    AttrStackList   attributeStack;
    Int             level;          // Current size of the (pseudo) stack

    friend ostream &operator << (ostream &s, const SLContext &ctx);
};


#endif

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