Better COM error handling.

[PsaltyDS]

Ref: Forum post 649304​http://www.autoitscript.com/forum/index.php?s=&showtopic=89906&view=findpost&p=649304

Request a standard and universally declared variable be included in the AutoIt environment (like $CmdLine and $CmdLineRaw) intended to hold the handle to the current COM Error Handler. Something like $oCOMError or $AutoItCOMErr.

Different UDFs using different naming conventions for the handler, leading to conflicts in proper handling. In the topic of the referenced post above, the error handlers for the _XMLDOMWrapper.au3 and IE.au3 UDFs collide.

If the AutoIt interpreter can cause something like $oAutoItCOMError to always reference the current error handler, like a ByRef, that would be great.

But if that is not feasible then perhaps just updating the documentation and putting the word out that every UDF should use the same variable name by convention would do it.

[TicketCleanup]

Automatic ticket cleanup.

[Valik]

Ehh, that's not the solution. The real problem is that it uses a global variable in the first place. The object should be passed as a parameter to the called function. Storing the object returned from ObjEvent() should be optional only if you want to unregister the event. That leads me to...

The whole system is flawed, honestly. It should be possible to register and unregister events. It should not require global variables. The return value should really be a pseudo-handle useful only to the unregister function. I'm not sure what to do about multiple events being registered to AutoIt.Error. It should probably call all registered handlers.

In short, I think the whole ObjEvent system needs rewritten to add two new functions and drastically altered behavior to be more logical. It's certainly an issue and I'll leave this open so that it's on the todo list.

[PsaltyDS]

Well, if it's that grand a project, it implies a long time frame to do it.

In the short term, given the constraints of the current system, the UDF writers referenced (eltorro and Dale) have done what they can. Both UDFs check if a handler already exists and avoid replacing it if it does. The problem for Dale in IE.au3 is that he has a function he knows will produce a COM error event and wants to silently sink it.

For him to temporarily replace the handler, he would have to release it and put it back afterwards, but has no way to do so because there is no way to know what variable name held the reference.

If all the UDF writers were encouraged to use $oAutoItCOMError or some logical common name, then they would be able to cooperate with each other. In IE.au3, Dale would then be able to save the old handler function name, release $oAutoItCOMError, apply his own temporary handler, then restore the old one to the same object variable name.

This is not better than rewriting the whole thing to make it "right", but it could be implemented with just some verbiage in the help file and few PMs to the most common UDF writers.

I don't even know if it makes sense in this context, but my wishful-thinking idea was that the special global variable $oAutoItCOMError would be a sort of ByRef itself so that $oAutoItCOMError = 0 would release the previous handler variable, no matter what it had been named, and $oAuotItCOMError = ObjEvent("AutoIt.Error", $sOldErrorHandler) would restore the old reference too (i.e. $oXMLMyError).

[Valik]

I will not add temporary code to solve a problem when I know it's not the right solution. Things either get fixed or they don't. I despise band-aids like what you describe.

[PsaltyDS]

Roger, out.

[Valik]

I'm not sure why this was assigned to Gary and changed to the UDFs component as the root cause of the problem has absolutely nothing to do with Gary or the UDFs. I'm changing the component back to AutoIt and modifying the title.

[trancexx]

Some aspects of COM error handler behavior have changed. Ticket is no longer valid.
Consult the documentation.