MDGContext Class Reference

#include <MDGContext.h>

Class Description

Dependency graph (DG) context class.

Control the way in which dependency nodes are evaluated.

DG contexts are used to define the way in which a dependency node is going to be evaluated. Examples of such contexts include "normal", "at a given time, "for a specific instance", etc.

MDGContext is mainly used in two places; within methods that trigger evaluations, to define what kind of evaluate is being requested, and within data blocks (MDataBlock), to identify how the data was created.

There is always the notion of the "current evaluation context". That's the one that will be used when no context is specifically mentioned, and is the normal state of evaluation.

Note

In the past the current and normal context were the same thing. With the advent of background evaluation and caching this is no longer necessarily true. Always use the current context, unless you mean to deliberately change to a specific context.

Examples:

Public Member Functions
	MDGContext ()
	Constructor. More...
	MDGContext (const MTime &when)
	Constructor. More...
	MDGContext (const MDGContext &in)
	Copy constructor. More...
	~MDGContext ()
	Destructor.
bool	isNormal (MStatus *ReturnStatus=NULL) const
	Determines if this context is that of "normal" evaluation. More...
MStatus	getTime (MTime &) const
	Return the single time for which this context is valid. More...
MDGContext &	operator= (const MDGContext &other)
	Assignment operator. More...
bool	isCurrent (MStatus *ReturnStatus=NULL) const
	Determines if this context is the one currently being used for evaluation. More...
const MDGContext	makeCurrent (MStatus *ReturnStatus=NULL) const
	Set the context to be the current evaluation context. More...

Static Public Member Functions
static const char *	className ()
	Returns the name of this class. More...
static const MDGContext	current ()
	Extract the current context being used for evaluation. More...

Friends
class	MPlug
class	MDataBlock

Constructor & Destructor Documentation

MDGContext

(

)

Constructor.

Creates a context to define the way in which a dependency node is evaluated. In this case the new context will be for a normal evaluation.

MDGContext

(

const MTime &

atTime

)

Constructor.

Creates a context to define the way in which a dependency node is evaluated. In this case the new context will be for an evaluation at a specific time.

Parameters

[in]

atTime

The time in which the evaluation will take place

MDGContext

(

const MDGContext &

other

)

Copy constructor.

Duplicates the given DG context.

Parameters

[in]

other

DG context to be copied.

Member Function Documentation

bool isNormal

(

MStatus *

ReturnStatus = NULL

)

const

Determines if this context is that of "normal" evaluation.

Parameters

[out]

ReturnStatus

Status code

Returns

• true this context is normal
• false this context is not normal

Status Codes:

• MS::kSuccess Method was successful
• MS::kFailure Object error

Examples:

MStatus getTime

(

MTime &

timeVal

)

const

Return the single time for which this context is valid.

The context must be a timed context, i.e. not a normal one.

Parameters

[out]

timeVal

Storage for the time

Returns

Status Code

Status Codes:

• MS::kSuccess The time was successfully returned
• MS::kFailure Context is not timed

MDGContext & operator=

(

const MDGContext &

other

)

Assignment operator.

Copies the RHS into this context.

Parameters

[in]

other

DG context to be copied.

const char * className ( )

static

Returns the name of this class.

Returns

Name of this class.

const MDGContext current ( )

static

Extract the current context being used for evaluation.

Returns

Current evaluation context

Examples:

bool isCurrent

(

MStatus *

ReturnStatus = NULL

)

const

Determines if this context is the one currently being used for evaluation.

Parameters

[out]

ReturnStatus

Status code

Returns

• true this context is currently being used for evaluation
• false this context is not currently being used for evaluation

Status Codes:

• MS::kSuccess Method was successful
• MS::kFailure Object error

const MDGContext makeCurrent

(

MStatus *

ReturnStatus = NULL

)

const

Set the context to be the current evaluation context.

Parameters

[out]

ReturnStatus

Status code

Returns

Previous current evaluation context

Status Codes:

• MS::kSuccess Method was successful
• MS::kFailure Object error

---

The documentation for this class was generated from the following files:

• MDGContext.h
• MDGContext.cpp