[每日一码] 从AcDbPolyline派生

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1. AcDb: deriving from AcDbPolyline
2. Published date: 2008-10-14
3. ID: TS47354
5. Applies to:
6. AutoCAD® 2009
7. AutoCAD® 2008
8. AutoCAD® 2007
10. 问题：
11. Deriving from AcDbPolyline works correctly, however, it seems DWG files
12. containing instances of my custom entity derived from AcDbPolyline do not
13. contain proxy graphic information for them. Why?
15. 解决方案：
16. AutoCAD does not save the proxy graphic information for classes derived from
17. AcDbPolyline. The reason for this is that the 'saveAs()' method is implemented
18. as follows:
21. void AcDbPolyline::saveAs(AcGiWorldDraw* mode, AcDb::SaveType st) {
22.     assertReadEnabled();
24.     if ( st == AcDb::kR12Save )
25.         // ... do something to convert into AcDb2dPolyline
26. }
27. Whereas it should be as follows:
30. void AcDbPolyline::saveAs(AcGiWorldDraw* mode, AcDb::SaveType st) {
31.     assertReadEnabled();
33.     if ( st == AcDb::kR12Save )
34.         // ... do something to convert into AcDb2dPolyline
35.     else
36.         worldDraw (mode) ;
37. }
38. As a result, proxy graphic data is never saved, which causes your derived
39. AcDbPolyline entity to be invisible if your DBX-object enabler application is
40. not loaded. Although this is not ideal, it does not affect any other behavior or
41. functionality of your custom entity.
43. A simple override of the 'saveAs()' method can solve this problem as follows:
45. 本帖隐藏的内容
46. void AcDbMyPolyline::saveAs(AcGiWorldDraw* mode, AcDb::SaveType st) {
47.     assertReadEnabled();
49.     if ( st == AcDb::kR12Save )
50.         AcDbPolyline::saveAs (mode, st) ;
51.     else
52.         worldDraw (mode) ;
53. }
54. This would be the correct solution, however there is another known problem in
55. AutoCAD that prevents the 'saveAs()' method from being called for proxy graphic
56. generation. This second problem is more serious because it prevents 'saveAs()'
57. method being called. The reason for this is that AutoCAD makes an exception in
58. the case of an AcDbPolyline entity. Instead of asking 'are you an AcDbPolyline
59. class?', AutoCAD asks 'Are you a "kind of" AcDbPolyline?' This also includes any
60. of your derived classes from AcDbPolyline.
62. The only solution is to pretend your custom AcDbPolyline entity is not an
63. AcDbPolyline class, even if it really is. This will cause AutoCAD to properly
64. call the 'saveAs()' method and then your implementation of the 'worldDraw()'
65. method for your custom entity. In order to pretend that it is not an
66. AcDbPolyline entity, just implement the 'ACRX采用DXF采用DEFINE采用MEMBERS' ARX macro as
67. follows:
69. ACRX采用DXF采用DEFINE采用MEMBERS(AcDbMyPolyline, AcDbCurve,
70. AcDb::kDHL采用CURRENT, AcDb::kMReleaseCurrent,
71. AcDbProxyEntity::kNoOperation,
72. ACDBMYPOLYLINE, ACDBMYAPP
73. );
75. There are other requirements in the implemention of the 'worldDraw()' method:
76. you should not call AcDbPolyline::worldDraw() when called from the 'saveAs()'
77. method because this would cause the same problem that was outlined previously.
78. (AutoCAD filters out all AcDbPolyline calls in that context). An 'unhandled
79. exception error' will occur as a result. (rememeber we are pretending not to be
80. an AcDbPolyline entity). To solve the problem, you need to modify the 'saveAs()'
81. method like this:
84. bool mbDrawWithExplode = false ;
86. void AcDbMyPolyline::saveAs(AcGiWorldDraw* mode, AcDb::SaveType st) {
87.     assertReadEnabled();
89.     if ( st == AcDb::kR12Save ) {
90.         AcDbPolyline::saveAs (mode, st) ;
91.     } else {
92.         mbDrawWithExplode = true ;
93.         worldDraw (mode) ;
94.         mbDrawWithExplode = false ;
95.     }
96. }
97. Implement your 'worldDraw()' method like this:
100. Adesk::Boolean AsdkOPLine::worldDraw(AcGiWorldDraw* mode)
101. {
102.     assertReadEnabled();
104.     if ( !mbDrawWithExplode ) {
105.         bPEdit =true ;
106.         if ( AcDbPolyline::worldDraw (mode) != Adesk::kTrue ) {
107.             bPEdit =false ;
108.             return (Adesk::kFalse) ;
109.         }
110.         bPEdit =false ;
111.     } else {
112.         AcDbVoidPtrArray ents ;
113.         AcDbPolyline::explode (ents) ;
114.         for ( int j =ents.length () - 1 ; j >= 0 ; j-- ) {
115.             ((AcDbEntity *)ents.at (j))->worldDraw (mode) ;
116.             delete (AcDbEntity *)ents.at (j) ;
117.         }
118.         ents.setLogicalLength (0) ;
119.     }
120.     return (Adesk::kTrue) ;
121. }
122. If you pretend it is not an AcDbPolyline, the AutoCAD "采用PEDIT" command will not
123. work for your custom entity anymore. If you do not intend to support "采用PEDIT",
124. then it is not a problem. However, if you intend to support "采用PEDIT" then you
125. need to pretend that it is an AcDbPolyline only for the "采用PEDIT" command. To
126. support "采用PEDIT" for a special class requires a considerable amount of work.
127. First, you need to rewrite the 'ACRX采用DXF采用DEFINE采用MEMBERS' ARX macro like this:
130. bool bPEdit =false ;
132. void set采用bPEdit (bool flag) {
133.     bPEdit =flag ;
134. }
136. //------------------------------------------
137. #define MY采用ACRX采用DEFINE采用MEMBERS(CLASS采用NAME) \
138. AcRxClass* CLASS采用NAME::desc() \
139. { \
140.    return (AcRxClass*)((AcRxDictionary*)acrxSysRegistry() \
141.         ->at(ACRX采用CLASS采用DICTIONARY))->at(bPEdit ? "AcDbPolyline" :
142. "AcDbMyPolyline"); \
143. } \
144. AcRxClass* CLASS采用NAME::isA() const \
145. { \
146.    return (AcRxClass*)((AcRxDictionary*)acrxSysRegistry() \
147.         ->at(ACRX采用CLASS采用DICTIONARY))->at(bPEdit ? "AcDbPolyline" :
148. "AcDbMyPolyline"); \
149. } \
150. AcRxClass* CLASS采用NAME::gpDesc = NULL
152. //----------------------------------------------------------------------
153. #define MY采用ACRX采用DXF采用DEFINE采用MEMBERS(CLASS采用NAME,PARENT采用CLASS,DWG采用VERSION,\
154.           MAINTENANCE采用VERSION,PROXY采用FLAGS,DXF采用NAME,APP) \
155. MY采用ACRX采用DEFINE采用MEMBERS(CLASS采用NAME); \
156. static AcRxObject * make##CLASS采用NAME() { return new CLASS采用NAME(); } \
157. void CLASS采用NAME::rxInit() { \
158.    if (CLASS采用NAME::gpDesc != NULL) \
159.     return; \
160.    CLASS采用NAME::gpDesc = newAcRxClass(#CLASS采用NAME, #PARENT采用CLASS, \
161.     DWG采用VERSION,MAINTENANCE采用VERSION,PROXY采用FLAGS, \
162.     &make##CLASS采用NAME, #DXF采用NAME, #APP); \
163. }
164. Replace the 'ACRX采用DXF采用DEFINE采用MEMBERS' ARX macro with the following definition:
167. MY采用ACRX采用DXF采用DEFINE采用MEMBERS(AcDbMyPolyline, AcDbCurve,
168.             AcDb::kDHL采用CURRENT, AcDb::kMReleaseCurrent,
169.             AcDbProxyEntity::kNoOperation,
170.             ACDBMYPOLYLINE, ACDBMYAPP
171. );
172. The last item you need to implement is an AcEditorReactor to detect when the
173. "采用PEDIT" command is executed and set the pPEdit flag to True as follows:
176. void AsdkEdReactor::commandWillStart(const TCHAR* cmdStr)
177. {
178. if ( 采用tcsicmp (cmdStr, 采用T("PEDIT")) == 0 )
179.   set采用bPEdit (true) ;
180. }
181. void AsdkEdReactor::commandEnded(const TCHAR* cmdStr)
182. {
183. if ( 采用tcsicmp (cmdStr, 采用T("PEDIT")) == 0 )
184.   set采用bPEdit (false) ;
185. }
186. void AsdkEdReactor::commandCancelled(const TCHAR* cmdStr)
187. {
188. if ( 采用tcsicmp (cmdStr, 采用T("PEDIT")) == 0 )
189.   set采用bPEdit (false) ;
190. }
191. void AsdkEdReactor::commandFailed(const TCHAR* cmdStr)
192. {
193. if ( 采用tcsicmp (cmdStr, 采用T("PEDIT")) == 0 )
194.   set采用bPEdit (false) ;
195. }

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