RFR: 8258754: Gracefully fallback to the OpenGL rendering pipeline if Metal rendering pipeline initialization fails

[Kevin Rushforth]

On Fri, 8 Jan 2021 19:16:05 GMT, Ajit Ghaisas <aghaisas at openjdk.org> wrote:

>>> 
>>> Maybe we can make this check version specific (maybe 10.12 for now) so
>>> that in future version when opengl is removed, then this check will be
>>> noop and if Metal fails, then it will quit.
>>> 
>>> Regards
>>> Prasanta
>> 
>> It is better to avoid version specific check when we can cover all the combinations discussed in other comments. My last commit addresses it.
>
> In the absence of specification, I have implemented the below combinations -
> 
> Current hard-coded Default pipeline is : OpenGL
> If user specifies : Nothing --> Selected pipeline is : Default
> If user specifies : opengl=true --> Selected pipeline is : OpenGL
> If user specifies : opengl=false --> Selected pipeline is : Metal
> If user specifies : metal=true --> Selected pipeline is : Metal
> If user specifies : metal=false --> Selected pipeline is : OpenGL
> If user specifies : opengl=true AND metal=false --> Selected pipeline is : OpenGL
> If user specifies : opengl=false AND metal=true --> Selected pipeline is : Metal
> If user specifies : opengl=true AND metal=true  --> Selected pipeline is : Default
> If user specifies : opengl=false AND metal=false  --> Selected pipeline is : Default
> 
> Note that - I have not considered the order of VM options. If needed, that should be handled separately later.
> 
> If selected pipeline could not be initialized, then the other pipeline is used as fallback.
> For fallback, appropriate message is logged only in verbose mode.
> If fallback also fails (unlikely) - then a RuntimeException with appropriate message is thrown.

Yes, I think this is what we what.

> Note that - I have not considered the order of VM options. If needed, that should be handled separately later.

I don't think this is possible (even if it were desired).

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PR: https://git.openjdk.java.net/lanai/pull/147