Re: DDC info refresh?

[Mouse <mouse%Rodents-Montreal.ORG@localhost>]

>> I've been investigating more, and it turns out all the
>> infrastructure is there - there is already such an event defined by
>> Xrandr.
> Do you mean "monitor connected" or "DDC info populated" as the event?

I meant "monitor connected", but "DDC info newly available" is perhaps
closer to what is actually possible.

>> In 8.0 it doesn't actually work - the event isn't sent upon monitor
>> connect or disconnect, at least not in the case of my test machine,
>> but is instead delayed until some (other) client queries state
> I've always wondered about this.  In my case, I've got some
> superstition that having the VGA HD15 connector present when the
> machine powers on has been needed in some cases.  I always felt like
> the DDC-getting mechanism was a bit of magic (which one of those pins
> carries that data?  I thought VGA was pretty much all analog...).

I don't know which pin(s) it is.  And it's been a while since I read
the description.  But I as I recall, there is a pin that carries
digital data from the monitor to the computer.  Memory is very fuzzy by
now, but I _think_ it's something like I²C slowed down by an order of
magnitude or two.

>> but there is no need to define a new event or a new event-carrying
>> mechanism or any of that.
> So, in your experimentation are you able to connect the VGA HD15 to
> the monitor after the system starts up, issue some xrandr command to
> gather DDC, then reset your video mode with that updated timing?

The sequence of my test was:

- Disconnect monitor cable
- Boot system
- Start X
- Verify (env DISPLAY=:0 xdpyinfo) that X started 800x600 and
   (env DISPLAY=:0 xrandr) that nothing higher-resolution is available
- Start my RandR-using test program, which selects for RandR events
   using XRRSelectInput
- Plug monitor in
- Nothing happens
- Issue xrandr command to query available options (no change specified)
- My program gets events
- That xrandr command reports 1024x768 and 1280x1024 available

If I've understood your question correctly, that's a "yes".

Of course, some aspects of this are likely to be hardware-specific; I
daresay not all hardware can notice monitor connect/disconnect.  Heck,
there's probably hardware out there that can't even fetch DDC info from
the monitor....

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