Introduction

MicroStation Python has a comprehensive API. It lets you into the core of MicroStation.

Often, we want to harvest information about DGN elements and models. Below are several utilities that operate on elements.

I keep those functions in their own Python file, named dgn_elements.py. That way, I can simply import that file and use its contents in my Python applications.

Hide the Underlying C Struct

MicroStation DGN elements are described by a C struct, which is linguistically anti-Pythonic. One reason for writing these functions is to hide that C struct. That is, you can call (for example) IsInvisible() without having to know about DgnElement.hdr.dhdr.props.b.invisible.

Implementation

from MSPyBentley import *
from MSPyBentleyGeom import *
from MSPyDgnPlatform import *
from MSPyMstnPlatform import *

# See: https://bentleysystems.service-now.com/community?id=community_question&sys_id=3950e8461b6612147171ff7e034bcb58
# Used with ChildElemIter
EXPOSE_CHILDREN_COUNT = ExposeChildrenReason(100)
EXPOSE_CHILDREN_QUERY = ExposeChildrenReason(200)
EXPOSE_CHILDREN_EDIT  = ExposeChildrenReason(300)

ELEM_HANDLER_GET_DESCR_MAX_LENGTH = 32
def GetElementDescription (element, string_length: int = ELEM_HANDLER_GET_DESCR_MAX_LENGTH, dgn_model: DgnModel = ISessionMgr.ActiveDgnModelRef.GetDgnModel())->str:
    '''
    Get the human-readable description of an element from an elementRef or ElementHandle.

    params:
    element [in] is an ElementHandle or ElementRef
    string_length [in] is the maximum length of the description string you want to accept; default to 32
    dgn_model [in] is a DGN model that contains element; defaults to the active model
    '''
    description = WString()
    if isinstance (element, ElementHandle):
        handler = element.GetHandler()
        if handler is None:
            MessageCenter.ShowErrorMessage(f"GetElementDescription() ElementHandle is invalid", None, False)
        else:
            handler.GetDescription (element, description, string_length)

    elif isinstance (element, PersistentElementRef):
        eh = ElementHandle (element, dgn_model)
        handler = eh.GetHandler()
        handler.GetDescription (eh, description, string_length)

    return str(description)

def GetElementById(element_id: int, dgn_model: DgnModel = ISessionMgr.ActiveDgnModelRef.GetDgnModel())->[bool, ElementHandle]:
    '''
    Get an element by its ID in the supplied DGN model.
    Returns: tuple (boolean: valid, Element Handle)
    params:
    element_id [in] the ID of the element to seek
    dgn_model [in] the DGN model that contains the element; default to the active model.
    '''
    eh = ElementHandle(element_id, dgn_model)
    valid = eh.IsValid()
    if not valid:
        msg = f"Element ID {element_id} is invalid"
        MessageCenter.ShowErrorMessage(msg, msg, False)

    return (valid, eh)

def GetUorsPerMeter (dgn_modelRef: DgnModelRef = ISessionMgr.ActiveDgnModelRef)->float:
    '''Get the ratio of units-of-resolution per meter for specified model.
    If you don't specify a model then the active model is assumed.'''
    dgn_model = dgn_modelRef.GetDgnModel()
    modelInfo = dgn_model.GetModelInfo()
    # Convert MicroStation units-of-resolution to meters
    uors: float = modelInfo.GetUorPerMeter()
    return uors

def GetUorsPerMaster (dgn_modelRef: DgnModelRef = ISessionMgr.ActiveDgnModelRef)->float:
    '''Get the ratio of units-of-resolution per master unit for specified model.
    If you don't specify a model then the active model is assumed.'''
    # Convert MicroStation units-of-resolution to master units
    uors: float = ModelRef.GetUorPerMaster(dgn_modelRef)
    return uors

def VerifyElementType (eh: ElementHandle, handlers: tuple)->bool:
    ''' Check that an element's class, represented by its element handler,
    matches at least one type in the handlers tuple '''
    handler = eh.GetHandler()
    return isinstance(handler, handlers)

def IsInvisible (eh: ElementHandle)->bool:
    ''' Determine whether a DGN element is visible.

    Wraps the DGN C-style element structure. '''
    return eh.GetElement().hdr.dhdr.props.b.invisible

def IsVisible (eh: ElementHandle)->bool:
    ''' Determine whether a DGN element is visible.

    Wraps the DGN C-style element structure. '''
    return not IsInvisible(eh)

def IsGraphical (eh: ElementHandle)->bool:
    ''' Determine whether a DGN element is graphical.

    Wraps the DGN C-style element structure. '''
    return eh.GetElement().ehdr.isGraphics

def IsDeleted (eh: ElementHandle)->bool:
    ''' Determine whether a DGN element is deleted. '''
    return eh.GetElement().ehdr.deleted

def GetElementClass (eh: ElementHandle)->DgnElementClass:
    ''' Return the DGN class (i.e. primary, construction etc) of a DGN element.

    Wraps the DGN C-style element structure. '''
    return eh.GetElement().hdr.dhdr.props.b.elementClass

def IsPrimaryClass (eh: ElementHandle)->bool:
    ''' Determine whether a DGN element is primary DGN class. '''
    return GetElementClass(eh) == DgnElementClass.ePrimary

def IsConstructionClass (eh: ElementHandle)->bool:
    ''' Determine whether a DGN element is primary DGN class. '''
    return GetElementClass(eh) == DgnElementClass.eConstruction

def IsVisibleGraphicalElement (eh: ElementHandle)->bool:
    ''' Determine that this is a visible graphical DGN element. '''
    return IsGraphical(eh) and IsVisible(eh)

def GetElementLevelId (eh: ElementHandle)->int:
    ''' Get the level ID of a graphic element.

    Wraps the DGN C-style element structure. '''
    if IsGraphical(eh):
        return eh.GetElement ().msElement.ehdr.level
    #else
    return 0

def IsClosedElement(eh : ElementHandle)->bool:
    ''' Determine whether this is a visible closed element. '''
    if (eh.IsValid() and IsVisibleGraphicalElement(eh)):
        path : CurveVector = ICurvePathQuery.ElementToCurveVector(eh)
        if path is None:
            return False
        return path.IsClosedPath()
    return False

def HasItem(eh : ElementHandle, libName: str, itemName: str)->bool:
    ''' Determine whether an element has a named Item in a named Item Type Library. '''
    if (eh.IsValid()):
        host: CustomItemHost = CustomItemHost(eh)
        if host.GetCustomItem(libName, itemName):
            return True

    return False

Questions

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