[OpenJDK 2D-Dev] RFR: 8229800 : WindowsServerCore 1809 does not provide d2d1.dll library required by awt.dll

[Sergey Bylokhov]

+1

On 8/27/19 10:34 am, Jayathirth Rao wrote:
> Hi Phil,
> 
> I went through the changes and I see that we are doing similar dynamic loading of d2d1.dll as we are doing for shcore.dll and loading code looks good.
> Also I confirmed that among the overloaded functions of D2D1CreateFactory, the one with 4 arguments is the generic one.
> 
> I have not verified build and logic by importing the code, but overall change looks good to me.
> 
> Thanks,
> Jay
> 
>> On 27-Aug-2019, at 9:27 PM, Phil Race <philip.race at oracle.com> wrote:
>>
>> bug: https://bugs.openjdk.java.net/browse/JDK-8229800
>> webrev : http://cr.openjdk.java.net/~prr/8229800/
>>
>> Since JDK 9, awt.dll has linked against d2d1.dll - a Direct2D library - in order to
>> call a method to get the screen dpi on Windows 7 and earlier.
>>
>> It appears that Windows Core Server used to include this library but recent
>> versions do not.
>>
>> As a result an app that loads AWT - even in headless mode - is DOA with
>> an unsatisfied link on start up and no work around is possible.
>>
>> Windows Core Server is meant to be used for server applications and
>> the use case here is just that but the hard compile time dependency
>> on d2d1.dll means that even if this code isn't reached, used, or needed
>> the app is still DOA.
>>
>> There may be other ways to get the screen DPI on Windows - I don't know
>> why the hidpi support chose this approach - but the safest change appears
>> to be to dynamically locate this library at run time.
>>
>> The callers of the internal GetScreenDpi function are already prepared
>> for it to "fail" and fall back to a default of 96 DPI.
>>
>> I have implemented this approach and verified it on Window 7 - which
>> is where it is needed. A regression test is difficult since setting values
>> like -Dsun.java2d.uiScale mean we over-ride and don't request this
>> setting and 96 dpi is the fallback so you could only test this as part
>> of overall true hidpi testing. And the focus of this bug - the absence
>> of a hard link against d2d1.dll and whether overall headless works
>> is best tested by running any headless app on Windows Core Server.
>>
>> One wrinkle in the code is that the lookup of the function name
>> needs to use the "C" binding so the signature is adjusted to match that.
>>
>> The bug is marked tck-red because of the DOA, but the proposal
>> is to just document that for JDK 13 GA this configuration isn't supported
>> and get the fix first into JDK 14 and then backport to 13.0.1 which gives
>> us a bit more time to verify the fix. It seems unlikely that this configuration
>> is critical for immediate adoption of 13 since it has taken 11 months for
>> this issue to be reported.
>>
>> -phil.
>>
>>
>>
> 


-- 
Best regards, Sergey.