[vdr] Re: can the osd be accessed by a separate pthread?

[Gunnar Roth <gunnar.roth@gmx.de>]

Klaus Schmidinger wrote:

> Clemens Kirchgatterer wrote:
>  
> > Klaus Schmidinger <Klaus.Schmidinger@cadsoft.de> wrote:
> >
> >    
> > > Clemens Kirchgatterer wrote:
> > >      
> > > > as i have already said: that is not the plugins fault. have you
> > > > tried this with any other plugin that opens an raw osd? i.e. with
> > > > klaus' own osddemo plugin?
> > > >        
> > > Sorry, but it _is_ the plugin's fault!
> > >
> > > A plugin that wants to open a raw OSD shall return a derived
> > > cOsdObject from its MainMenuAction() function. VDR will then call that
> > > object's Show() function and in _there_ the derived cOsdObject may
> > > call cOsd::OpenRaw()(and nowhere else!).
> > >      
> > are you absolutly shure, that there is a difference between opening
> > the RawOsd in cOsdObject->Show() as you say and doing it in a thread
> > spawned from cOsdObject->Show() ? i can't see why this should matter.
> >    
> You're right, this shouldn't matter..
>  
Ok this means the rule is. OpenRaw must only be called after 
cOsdObject->Show() has been called, but before the destructor of

cOsdObject is called. In the destructor the osd must be closed. 

And it is the case, that an StatusMessage issued from svdrsend.pl results in the desctruction of the current
cOsdObject ?


> The plugin has to make sure that it has deleted the osd before the
>
> destructor returns. If the osd has been allocated in the thread, the
> destructor has to make sure that the thread has completely ended and released
> the osd _before_ it returns.
>
> Klaus
>  
Hmm the race condition ist there. The destructor of tetris just set the 
running flag to false and returns at once,
while the thread is still running for a while and access the osd. the 
result is a disturbed picture and sound and wrong osd display
of a status message.

Well, now i understood how i can use the osd from a separate thread and 
do not interfere with vdr core.

thanks for the discussion of the topic.

this should really be added to PLUGINS.html. ;-)


regards,
gunnar







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