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

[Alexey Ushakov]

> On 7 Jan 2021, at 10:28, Ajit Ghaisas <aghaisas at openjdk.java.net> wrote:
> 
> On Thu, 7 Jan 2021 06:32:59 GMT, Sergey Bylokhov <serb at openjdk.org> wrote:
> 
>> Does this check mean that the MTLRenderQueue.sync() is not a noop if the metal is not enabled?
> 
> I don't know how else we will differentiate between Metal and OGL here.
> MTLRenderQueue.sync() is still a noop - as there is null instance check inside it.
> The comment above the if check has become stale - I will update it.
> 
>> src/java.desktop/macosx/classes/sun/awt/CGraphicsDevice.java line 71:
>> 
>>> 69: 
>>> 70:         // Check whether -Dsun.java2d.metal=true has been specified
>>> 71:         if (MacOSFlags.isMetalEnabled()) {
>> 
>> Is it possible to use metal and OGL at the same time on different devices? I think it is better to move these checks to the CGraphicsEnvironment.makeScreenDevice(), similar Win32GraphicsEnvironment.makeScreenDevice()
> 
> I am not sure why someone wants to use different pipelines on different devices? and should we support it?
> On Windows we do that as a fallback to overcome a limitation of WGL - that's what I could infer from code in W32GraphicsDevice.getDefaultConfiguration()

I also think that it’s not a good idea to have both OGL and Metal enabled at the same time. It seems like it’s not a common scenario for client apps, so we may have some problems that Apple doesn’t even know about. Anyway OGL is now deprecated technology on Mac. 

Best Regards,
Alexey


> 
> I doubt whether we can add these checks in CGraphicsEnvironment.makeScreenDevice() - as we do not have specific MTLGraphicsDevice and CGLGraphicsDevice classes. That's the reason this method is currently unsupported.
> 
> Win32GraphicsEnvironment.makeScreenDevice() - creates either D3DGraphicsDevice or Win32GraphicsDevice based on whether isD3DEnabled. 
> Win32GraphicsDevice in turn uses either WGLGraphicsConfig or Win32GraphicsConfig based on whether OGL is enabled.
> 
> I felt CGraphicsDevice (similar to Win32GraphicsDevice) can differentiate between metal or OGL. Hence, I have added checks here.
> 
> -------------
> 
> PR: https://git.openjdk.java.net/lanai/pull/147