[Vm-dev] Re: [squeak-dev] what's the standard way of finding out from Smalltalk if one is running headless?

Levente Uzonyi leves at elte.hu
Wed Aug 31 21:33:28 UTC 2011

On Wed, 31 Aug 2011, Igor Stasenko wrote:

> On 31 August 2011 18:28, Eliot Miranda <eliot.miranda at gmail.com> wrote:
>> I thought to test things like Display extent & DisplayScreen
>> actualScreenDepth but these either fall back to values in the pre-headless
>> image or don't fail and answer the actual display depth, even though the VM
>> is running headless (at least on Mac they do).
> ahaa! you seem to be facing same problems as we had :)
> Nothing. I found no reliable way to detect that image are running
> headless, there is no VM api for exposing that. And this is sad.
> The way how pharo images detecting it currently is to check a
> command-line arguments passed to VM.
> See
> SmalltalkImage isHeadless
> in pharo 1.3 - 1.4 images.
> it is ugly, but i think this is better than detecting via Display,
> because its more direct.
> We should fix that.
> either by adding a new primitive , or adding new system attribute..
> But my personal preference is to let image control the headless mode,
> i.e. instead of making VM decide whether image should be forced to run
> headless or not,
> an image should check a command line,
> and then instruct VM to create a window or not.

Running "headless" has nothing to do with having windows or not. We're 
running our images with vm-display-none, but we're still use windows, 
because we connect to our images via RFB.

Since RFB also uses Display, therefore detecting headless mode with 
Display checks is not trivial.


> This IMO would be the best solution to the problem. VM should provide
> access to features and/or facilities, and image should decide whether
> use them or not.
> Even if VM decides to not allow UI, then it should report to an image
> that given facility is not available, and play with it in nice manner,
> but not like today when image has no idea what happens
> and leaving it without any clues in what environment it running.
> -- 
> Best regards,
> Igor Stasenko AKA sig.

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