RFR: 8324941: POC for Headless platform for JavaFX [v4]

[Marius Hanl]

On Thu, 26 Jun 2025 21:02:26 GMT, Andy Goryachev <angorya at openjdk.org> wrote:

>> This is a good question, and I believe it is part of a broader discussion. There are a number of places (e.g. here) where I use hardcoded, default values which should be fine for most usecases I'm aware of. However, I believe there is definitely value in having more configurable values (e.g. in screen dimensions, but also number of screens, default window sizes, multiclick values etc).
>> The challenge with this is that we need some way to have developers manipulate these values, for example using system properties (as you state as well). This is then adding a feature that doesn't exist yet, so it would require a deeper discussion on how to make the Headless platform configurable. I'm absolutely +1 on that, but I believe it would be easier if we do that as a follow-up?
>
> I was going to suggest a system property like
> 
> -Dheadless.screens="1920x1024"
> -Dheadless.screens="1920x1024x16"
> 
> to be able to configure the screen resolution and the bit depth (and maybe a scale as well).
> 
> I don't know whether supporting multiple screens makes sense here, but perhaps for testing?
> 
> And, if the code cannot parse the property it would default to something reasonable like 1280x768 or slightly larger?

> I'm absolutely +1 on that, but I believe it would be easier if we do that as a follow-up?

I agree, makes sense. This way, we can also gradually add properties as (if) needed.

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PR Review Comment: https://git.openjdk.org/jfx/pull/1836#discussion_r2171270789