从AcDbPolyline派生

LoveArx

AcDb: deriving from AcDbPolyline
Published date: 2008-10-14
ID: TS47354

Applies to:
AutoCAD® 2009
AutoCAD® 2008
AutoCAD® 2007

问题：
Deriving from AcDbPolyline works correctly, however, it seems DWG files
containing instances of my custom entity derived from AcDbPolyline do not
contain proxy graphic information for them. Why?

解决方案：
AutoCAD does not save the proxy graphic information for classes derived from
AcDbPolyline. The reason for this is that the 'saveAs()' method is implemented
as follows:


void AcDbPolyline::saveAs(AcGiWorldDraw* mode, AcDb::SaveType st) {
    assertReadEnabled();

    if ( st == AcDb::kR12Save )
        // ... do something to convert into AcDb2dPolyline
}
Whereas it should be as follows:


void AcDbPolyline::saveAs(AcGiWorldDraw* mode, AcDb::SaveType st) {
    assertReadEnabled();

    if ( st == AcDb::kR12Save )
        // ... do something to convert into AcDb2dPolyline
    else
        worldDraw (mode) ;
}
As a result, proxy graphic data is never saved, which causes your derived
AcDbPolyline entity to be invisible if your DBX-object enabler application is
not loaded. Although this is not ideal, it does not affect any other behavior or
functionality of your custom entity.

A simple override of the 'saveAs()' method can solve this problem as follows:

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When the "_PEDIT" command starts, the AsdkEdReactor::commandWillStart() reactor
callback is called and the bPEdit Boolean is set to True. Then AutoCAD verifies
that the entity selected is "kind of" an AcDbPolyline. To do this AutoCAD calls
the AcRxObject::isKindOf() method, this in turn calls the class descriptor of
the entity (AcDbMyPloyline::desc()), which returns the AutoCAD AcDbPolyline
class descriptor. In all other situations, it returns a real custom entity class
descriptor (child of AcDbCurve).

Forward Compatibility Issues
The two problems will be fixed in a later release of AutoCAD, it should be asked
if the custom entity derived from AcDbPolyline will continue to work. Although a
custom entity derived from AcDbPolyline will continue to work, you will also be
allowed to remove the workarounds in this solution without any problems,
including reloading files from one implementation to another.

weizcw2008

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Throne

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基于中

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nacl_cn

这是关于什么的问题啊？

zxc_000

看看楼主的分享

1121443108qaz

我来看看看代码

wkur

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机械工人

很好，干得好

gis2000

不知道有什么用

Cherish易

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cable2004

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