[CS3] Whats the best way to track model changes? Document Observer? Selection Observer?

Question

Hello,<br /><br />Usecase I am working on needs to track following events:<br />1. A page item was created/deleted/resized/moved/etc..<br />2. A text was inserted/deleted<br />3. A page was created/deleted<br /><br />Since the list is quite broad I am wondering if there are known best practices to follow. <br /><br />I have tried attaching to Command manager via Document Observer:<br /><br />  InterfacePtr<IDocument> iDocument(this, UseDefaultIID());<br />  InterfacePtr<ISubject> iSubject(iDocument, UseDefaultIID());<br />  iSubject->AttachObserver(ISubject::kRegularAttachment,this, IID_ICOMMANDMGR, IID_IMYDOCOBSERVER);<br /><br />Then during "update" call:<br /><br />  if (protocol != IID_IHIERARCHY_DOCUMENT) break;<br /><br />  ICommand* iCommand = (ICommand*)changedBy;<br />  if (iCommand->GetCommandState() != ICommand::kDone) break;<br /><br />  const UIDList itemList = iCommand->GetItemListReference();<br />  if (itemList == nil || itemList.IsEmpty()) break;<br /><br />  ClassID commandClassID = ::GetClass(iCommand);<br />  if(commandClassID.Get() == kAddToHierarchyCmdBoss || kPlacePICmdBoss) {<br />      // do something at new item creation<br />  }<br /><br />Problem is "kAddToHierarchyCmdBoss" is not just the one command that is sent while creating a new item. There are dozen others and hence I am not sure if I am watching the right one.<br /><br />Second I tried implementing a selection observer and hope to use HandleSelectionAttibuteChanged. A quick search didnt resulted in any suite that lets me implement my use cases.<br /><br />I was inclined towards command observer because thats at low enough level (and right above database layer) allowing me to trap all model changes.<br /><br />I am not looking for a specific answer/code but more of a guideline how to approach the problem.<br /><br />Suggestions? Comments? Thanks in advance

Answer 1

There is no silver bullet, and while the command mgr can be useful to find out what's going on in general, it is definitely not the place for own dispatching. You'll have to revisit every command before and after execution, and plenty obscure sub-commands nested within larger sequences. If you handle them all this will seriously degrade performance. One good use of command manager notifications is to yield and inspect the matching commands for UI activities, from within your debug build.
In your quoted update(), when you check the protocol you're anyway already discarding the command mgr notifications, because the protocol then would be IID_ICOMMANDMGR. Probably you already have attached a bunch of other protocols?
Comparing to previous versions, the changes listed in 1) are pretty simple, you just subscribe at the document boss, and listen for the protocols IID_IHIERARCHY_DOCUMENT, IID_ITRANSFORM_DOCUMENT, eventually IID_IGEOMETRY_DOCUMENT, IID_IPATHGEOMETRY_DOCUMENT, IID_IINVALSHAPE. These also have an advantage that you get a meaningful theChange (rather than the command mgr's kBeforeDoMessageBoss and alike) and can dispatch on those.
If you have a previous version of InDesign, there used to be a wildcard protocol IID_IPMUNKNOWN that would yield any notifications on the subject so you could dump them out and search for details. Apparently for performance reasons this was removed with CS3 after some plugins used it for release code, IMO Adobe should just have limited the feature to the debug build.
Besides to observers, the service registry is full of other notifications, have a look the the cross reference in sdkdocs/html/classISignalMgr.html for the most prominent ones. One exception here, 2) For text edits, you won't even use observers or signals but kEditCmdPreProcessService / IID_ITEXTEDITPREPROCESS service instead, or its sister IID_ITEXTEDITPOSTPROCESS.
3) Probably you'll again observe the kDocBoss for IID_ISPREADLIST and IID_IMASTERSPREADLIST.
Regarding selection observers and suites, we're talking model changes here so please just forget about them in this place. Selection observers are used to follow the selection from within UI widgets, such as a palette or control strip.
Regards,
Dirk