python/api1/py1BlindDoubleDataCmd.py

#-
# ==========================================================================
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########################################################################
# DESCRIPTION:
#
# Produces the Python command "spBlindDoubleDataCmd" and user defined data
# type "spBlindDoubleData".
#
# This plug-in demonstrates how to create blind data (dynamic attributes) based
# on user defined data types. The plug-in uses a simple double value as the user
# data type. The use of the MPlug class to set and retrieve the value of the
# attribute is demonstrated, as are read and write routines that implement
# the storage and retrieval of the data in both Maya ASCII and Maya Binary file
# formats.
#
# To use this plug-in, select a dependency node, and then issue the command: 
#
#   maya.cmds.spBlindDoubleData()
#
# A dynamic attribute containing the double value 3.2 will be attached to each
# selected dependency node. If the scene is saved in Maya ASCII format, you will
# be able to see the Python commands that save the value of the dynamic attribute.
# If the scene is reloaded, the dynamic attribute will be reattached to the
# applicable nodes. 
#
########################################################################

# import maya.cmds
# maya.cmds.loadPlugin("blindDoubleDataCmd.py")
# maya.cmds.sphere()
# maya.cmds.spBlindDoubleData()

from builtins import next
import sys
import maya.OpenMaya as OpenMaya
import maya.OpenMayaMPx as OpenMayaMPx

kPluginName = "spBlindDoubleData"
kPluginDataId = OpenMaya.MTypeId(0x0008006D)

#
fValueDictionary={}

# testing function
def printMsg(msg):
    print(msg)
    stream=OpenMaya.MStreamUtils.stdOutStream()
    OpenMaya.MStreamUtils.writeCharBuffer(stream,msg)

# data
class blindDoubleData(OpenMayaMPx.MPxData):
    def __init__(self):
        OpenMayaMPx.MPxData.__init__(self)
        self.__fValue = 0.0
        fValueDictionary[OpenMayaMPx.asHashable(self)]=self.__fValue

    def readASCII(self, args, lastParsedElement):
        try:
            if args.length() > 0:
                parsedIndex = OpenMaya.MScriptUtil.getUint(lastParsedElement)
                self.__fValue = args.asDouble( parsedIndex )
                parsedIndex += 1
                OpenMaya.MScriptUtil.setUint(lastParsedElement,parsedIndex)
                fValueDictionary[OpenMayaMPx.asHashable(self)]=self.__fValue
        except:
            sys.stderr.write("Failed to read ASCII value.")
            raise

    def readBinary(self, inStream, length):
        readParam = OpenMaya.MScriptUtil(0.0)
        readPtr = readParam.asDoublePtr()
        OpenMaya.MStreamUtils.readDouble(inStream, readPtr, True )
        self.__fValue = readParam.getDouble(readPtr)

    def writeASCII(self, out):
        try:
            OpenMaya.MStreamUtils.writeDouble(out, self.__fValue, False)
        except:
            sys.stderr.write("Failed to write ASCII value.")
            raise

    def writeBinary(self, out):
        try:
            OpenMaya.MStreamUtils.writeDouble(out, self.__fValue, True)
        except:
            sys.stderr.write("Failed to write binary value.")
            raise

    def copy(self, other):
        # Cannot convert other to self.  Use a dictionary
        # to hold the information we need.
        self.__fValue = fValueDictionary[OpenMayaMPx.asHashable(other)]

    def typeId(self):
        return kPluginDataId

    def name(self):
        return kPluginName

    def value(self):
        return self.__fValue

    def setValue(self, newVal):
        self.__fValue = newVal

# command
class blindDoubleDataCmd(OpenMayaMPx.MPxCommand):
    def __init__(self):
        OpenMayaMPx.MPxCommand.__init__(self)
        self.__iter = None

    def doIt(self, args):
        selList = OpenMaya.MSelectionList()
        OpenMaya.MGlobal.getActiveSelectionList(selList)
        self.__iter = OpenMaya.MItSelectionList(selList)
        self.redoIt()

    def redoIt(self):
        dependNode = OpenMaya.MObject() # Selected dependency node
        # show message and advance iterator
        def error(msg):
            sys.stderr.write(err)
            next(self.__iter)
            
        # Iterate over all selected dependency nodes
        #
        while not self.__iter.isDone():
            # Get the selected dependency node and create
            # a function set for it
            #
            try:
                self.__iter.getDependNode(dependNode)   
            except:
                error("Error getting the dependency node")
                continue

            try:
                fnDN = OpenMaya.MFnDependencyNode(dependNode)
            except:
                error("Error creating MFnDependencyNode")
                continue

            # Create a new attribute for our blind data
            #
            fnAttr = OpenMaya.MFnTypedAttribute()
            newAttr = fnAttr.create("blindDoubleData", "BDD", kPluginDataId)
            
            # Now add the new attribute to the current dependency node
            #
            fnDN.addAttribute(newAttr, OpenMaya.MFnDependencyNode.kLocalDynamicAttr)

            # Create a plug to set and retrive value off the node.
            #
            plug = OpenMaya.MPlug(dependNode, newAttr)

            # Instantiate blindDoubleData and set its value.
            #
            newData = OpenMayaMPx.asMPxPtr(blindDoubleData())
            newData.setValue(3.2)

            # Set the value for the plug.
            #
            plug.setMPxData(newData)

            # Now try to retrieve the value off the plug as an MObject.
            #
            try:
                sData = plug.asMObject()
            except:
                error("Error getting value off plug")
                continue
                
            # Convert the data back to MPxData.
            #
            pdFn = OpenMaya.MFnPluginData(sData)
            data = pdFn.constData()

            # Get the value.
            #
            if not data:
                error("Error: failed to retrieve data.")
                continue
                
            next(self.__iter)

    def undoIt(self):
        pass

    def isUndoable(self):
        return True


########################################################################


# Creators
def cmdCreator():
    return OpenMayaMPx.asMPxPtr(blindDoubleDataCmd())

def dataCreator():
    return OpenMayaMPx.asMPxPtr(blindDoubleData())

# Initialize the script plug-in
def initializePlugin(mobject):
    mplugin = OpenMayaMPx.MFnPlugin(mobject, "Autodesk", "1.0", "Any")
    try:
        mplugin.registerData(kPluginName, kPluginDataId, dataCreator)
    except:
        sys.stderr.write("Failed to register new data type: %s\n" % kPluginName)
        raise
        
    try:
        mplugin.registerCommand(kPluginName, cmdCreator)
    except:
        sys.stderr.write("Failed to register command: %s\n" % kPluginName)
        raise


# Uninitialize the script plug-in
def uninitializePlugin(mobject):
    mplugin = OpenMayaMPx.MFnPlugin(mobject)
    try:
        mplugin.deregisterCommand(kPluginName)
    except:
        sys.stderr.write("Failed to unregister command: %s\n" % kPluginName)
        raise

    try:
        mplugin.deregisterData(kPluginDataId)
    except:
        sys.stderr.write("Failed to unregister data type: %s\n" % kPluginName)
        raise