RFR: 8185862: AWT Assertion Failure in ::GetDIBits(hBMDC, hBM, 0, 1, 0, gpBitmapInfo, 0) 'awt_Win32GraphicsDevice.cpp', at line 185 [v5]

[Christoph Langer]

On Fri, 16 Feb 2024 21:50:09 GMT, Phil Race <prr at openjdk.org> wrote:

> The first thing I worry about here is that the obvious implication is that we can now have zero monitors. Even if the monitor were not usable, that seems to have been "OK" in practice so long as we didn't assert out in a debug build. Have you looked for any subsequent code that might break with zero monitors ?

I think that's hard to find out. At least our regression testing did not show issues. The change probably needs more testing. On the other hand, I think the risk with that change is low since the environment that is addressed by it seems to be rather unusual and the asserts show that something goes wrong in that case currently anyway.

> The 2nd thing is that this situation ought to clearly flag that this is a HEADLESS situation and the AWT should be in headless mode. And that decision usually needs to be made very early. So is this code path involved in that decision. It seems likely there's a missing piece since I don't know that we even properly make that decision on windows like we do on Linux.

That's a valid point. We could flag a system where we detect zero monitors as headless and then set the headless property. At the moment the default headless property would be false on Windows in any case, as per [here](https://github.com/openjdk/jdk/blob/f365d807e5552a6ad9a36afd82db8f0881d62cc3/src/java.desktop/windows/classes/sun/awt/PlatformGraphicsInfo.java#L41). I guess we can wire the monitor detection in here and return true if no monitors were found. Would you want me to go that way?

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PR Comment: https://git.openjdk.org/jdk/pull/17614#issuecomment-1959528168