[PATCH xserver] present: Handle event mask updates as specified

[Michel Dänzer]

On 29.07.2016 01:54, Keith Packard wrote:
> Michel Dänzer <michel at daenzer.net> writes:
> 
>> Without this change, there's no way for a client to explicitly change
>> or destroy an existing event mask entry. Trying to do so as specified
>> above would actually result in a new entry being created with
>> the mask value passed in.
> 
> Yup, this looks like a good thing to fix.
> 
> Instead of walking the linked list, you should perform a resource lookup
> instead using the provided ID; that would be more consistent, and would
> let you catch errors where the provided resource ID was actually being
> used on a different window. If it does, you should return a Match error.
> 
> You've also lost the call to LEGAL_NEW_RESOURCE in the path which
> creates a new event.
> 
>> While we're at it, fix a memory leak if AddResource fails.
> 
> You've made a very common mistake -- AddResource actually calls the
> delete function when it fails, so you don't need to free the object in
> the failure path.
> 
> Here's an alternate (untested) patch which shows what I meant; use
> whatever bits of this seem useful.

Thanks, I incorporated almost all your changes in v2, with the exception
of not calling LEGAL_NEW_RESOURCE if mask == 0, due to this spec language:

 If eventContext is an unused XID, then if eventMask is empty
 no operation is performed.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer

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