Re: USPosition vs. PPosition with Virtual viewports

[Sasha Vasko <sasha aftercode net>]

Carsten Haitzler (The Rasterman) wrote:

> On Mon, 24 Oct 2005 22:07:19 +0200 Lubos Lunak <l lunak suse cz> babbled:
>
>
> > Dne čt 20. října 2005 03:29 Carsten Haitzler napsal(a):
> >
> > > On Wed, 19 Oct 2005 15:30:00 -0500 Sasha Vasko <sasha aftercode net> 
> >
> > babbled:
> >
> > > > There is a certain ambiguity in how geometry should be specified by
> > > > user, when Window Manager is supporting virtual viewports. This surfaced
> > > >  as the result of GIMP abuse of USPosition flag which is outlined here
> > > >
> > > > : http://bugzilla.gnome.org/show_bug.cgi?id=319099
> > > >
> > > > Basically, for user to be able to place , say, a term window into
> > > > arbitrary viewport on the desktop, using just a command-line options -
> > > > geometry must be specified in relation to the desktop origin, there is
> > > > no other way around it. Therefore it is a duty of a Window Manager to
> > > > always treat USPosition in relation to a desktop origin.
> > > >
> > > > On the other hand, as apps itself may not be aware of existence of
> > > > virtual viewports, and even if they do - its not possible to reliably
> > > > take it into consideration - PPosition must always be treated in
> > > > relation to the current viewport's origin.
> > > >
> > > > Now this is not a transparent conclusion for anyone not involved with
> > > > window management to a certain depth, and therefore I suggest that this
> > > > should be clarified in specs under "Desktop/workspace model" subsection
> > > > of Implementation notes.
> > > >
> > > > Anybody wants to comment on that ?
> > >
> > > this is a tough one. most existing apps will see BOTH USPosition and
> > > PPosition as ROOT window relative co-ordinate hints (out of practicality
> > > and a loong history). changing this will mean breakage of at least some
> > > apps. but this also makes using a virtual desktop + movable viewport a bit
> > > of a nightmare,as i assume you are discovering.
> > >
> > > basically a lot of wm's have ignored pposition in the past due to abuse by
> > > apps (like netscape) and thus many aps have moved to abusing usposition
> > > instead (though they do it better than netscape did). i know that
> > > personally im gettigng to the point of encouraging users to use the lock
> > > and override features of the wm to say "dont listen to the apps request for
> > > position, size etc. use mine and ignore the app" as its geenralyl more
> > > reliable :) thus in that scneario - the wm can choose to put the app where
> > > it was last - relative to the virtual desktop co-ordinates, not the
> > > viewport. :)
> >
> > Does somebody think it wouldn't be completely naive to try to fix this 
> > USPosition/PPosition madness by adding some kind of I-do-it-properly property 
> > that both WMs and apps could set?
> >
> > Qt also sets both US and P positions, because of the reasons listed above,
> > in order to work around broken old WMs and whatnot, and I've run already into 
> > this a couple of times with KWin. Qt e.g. always places dialogs, and although 
> > KWin has much better placement algorithm it's simply not of much use because 
> > of US and P position set. I even tried to actually ignore those flags in 
> > general for dialogs but that wasn't that good idea either :( . And having the 
> > user to manually set setting for every app is not really a solution.
>
>
> agreed - for the aqverag user. power users when they get annoyed enough will
> set it. :)
>
> as for a new hint - i don't see this as a bad idea, but if we were to propose
> such a hint - may i suggest we expand it a bit. we should:
>
> 1. provide another client window id (that should be mapped at the time) to
> place RELATIVE to. (if not provided root is assumed). 2. a flag to indicate if
> the position is screen relative (viewport relative) or desktop relative. 3. the
> ability to provide absoloute position offsets relative to the top-left (or any
> other corner) but ALSO relative percentage offsets (as a percentage of the
> relative window mentioned in 1. and its geometry at the time the window is
> mapped.

Woa! Hold On! :)
That's a whole different aspect you are bringing in here.
As I see it we have two problems here now :
1) Let client apps know how Window Manager handles USPosition and PPosition
2) Possibly allow clients to request placement in relation to desktop
origin or another window ( which is what you are bringin up ).

As to first problem I agree with Lubos, and here is what we could do :

_NET_PLACEMENT, ATOM[]/32

With possible atoms :
	_NET_PPOSITION
	_NET_USPOSITION
	_NET_USPOSITION_IS_DESKTOP_RELATIVE

For the second problem, I'd say it will be good enough if we'll allow
clients to request position in relation to its other windows, but not
root or viewport, as those should be dictated by window manager's own
policy. Even that is to much IMHO. and I think we need to start a second
thread for that discussion.


Sasha Vasko