On 21 January 2011 11:04, Sven Van Caekenberghe <sven@beta9.be> wrote:
Igor,
Headless support is an important feature. It should be something simple so that it can be used in many ways. I would suggest to read chapter 20 of the VW Application Developers Guide (it is only 10 pages).
They basically have the option to toggle between headless and headfull. This is not detected automatically, but a global switch (with a test method).
In headless mode all display access results in an error.
yes.
In headless mode all Transcript output (can/is) also sent to a file (stdout would be another option).
yes
What is interesting (and we might make that an option) is that the 'no display' error results in the image being saved 'headfull' so that you can start it up using a display to debug it (suspended process/debugger).
That could be done.. but not as userful as simply report an error. Usually we (developers) knowing what we want to do, and what i don't want to see in my headless image is any attempts to access display/ui.
Saving a headless image headfull can also be done programmatically.
I don't think more than that is needed. There are many options to interact with headless images, forcing one on people would not be good, the same goes for command line parsing, preferences, startup files, ... These other options could become separate projects.
well, again, when people running image(s) in headless mode, they are know what they doing, and i think their default expectation is that image(s) should be aware that it runs headless and do not try to invoke anything which requires user interaction (like yes/no dialog) , because this does not makes any sense.
I would be an interested user and if I can will try to help.
Regards,
Sven
-- Best regards, Igor Stasenko AKA sig.