RFR: 8354415: [Ubuntu25.04] api/java_awt/GraphicsDevice/indexTGF.html#SetDisplayMode - setDisplayMode_REFRESH_RATE_UNKNOWN fails: Height is different on vnc

[Alexander Zvegintsev]

On Tue, 15 Jul 2025 04:32:36 GMT, Harshitha Onkar <honkar at openjdk.org> wrote:

>> On Linux, we are currently use XRRSetScreenConfigAndRate to change the display mode. This works in most cases, except for some VNC-configured hosts, where the display change may not occur.
>> One of the conformance tests fails on these hosts.
>> 
>> It was discovered, that the xrandr utility app works fine on these hosts and uses the Crtc and Output Randr APIs, which provide more fine-grained control over display settings.
>> 
>> This changeset utilizes the Crtc and Output Randr APIs to change the display mode.
>> 
>> Currently, changing the display mode is only [available when running a single screen](https://github.com/openjdk/jdk/blob/a86dd56de34f730b42593236f17118ef5ce4985a/src/java.desktop/unix/classes/sun/awt/X11GraphicsDevice.java#L365).
>> This limitation remains, but we may remove it in the future. A separate issue [has been filed](https://bugs.openjdk.org/browse/JDK-8361968) for this purpose.
>> 
>> The `awt.x11useOldConfigDisplayMode` system property enables the old behavior. Perhaps there's a better name for it.
>> 
>> Testing looks good on VNC and local machines.
>
> src/java.desktop/unix/native/common/awt/awt_GraphicsEnv.h line 65:
> 
>> 63: };
>> 64: 
>> 65: #define MAX_DISPLAY_MODES 256
> 
> File requires copyright year update

It can be handled as a batch copyright year update.

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PR Review Comment: https://git.openjdk.org/jdk/pull/26268#discussion_r2206491921