[PATCH] xdg-shell: clarify popup constrain's slide mechanism

[Mike Blumenkrantz]

On Wed, 23 Nov 2016 12:05:12 -0800
Bill Spitzak <spitzak at gmail.com> wrote:

> Much better to just say one of the "constraints" is that the child
> must touch the parent.
> 
> The specified api, despite attempts to prevent it, still allows
> starting positions that don't touch the parent (this can be achieved
> by using the offset, the restriction that the anchor rectangle be
> inside the parent does not help). So changing the definition of
> "constraints" to this would allow a position to fail if it does not
> touch, even before "sliding".
> 
> 
> On Mon, Nov 21, 2016 at 3:52 AM, Jonas Ådahl <jadahl at gmail.com> wrote:
> > On Mon, Nov 21, 2016 at 06:36:49AM -0500, Mike Blumenkrantz wrote:  
> >> On Fri, 18 Nov 2016 09:28:56 +0800
> >> Jonas Ådahl <jadahl at gmail.com> wrote:
> >>  
> >> > On Wed, Nov 16, 2016 at 10:23:59AM -0500, Mike Blumenkrantz wrote:  
> >> > > some restrictions must be placed on this or else it becomes legal for
> >> > > the compositor to place popups in unexpected locations when sliding
> >> > > is allowed
> >> > >
> >> > > Signed-off-by: Mike Blumenkrantz <zmike at osg.samsung.com>
> >> > > ---
> >> > >  unstable/xdg-shell/xdg-shell-unstable-v6.xml | 6 ++++--
> >> > >  1 file changed, 4 insertions(+), 2 deletions(-)
> >> > >
> >> > > diff --git a/unstable/xdg-shell/xdg-shell-unstable-v6.xml b/unstable/xdg-shell/xdg-shell-unstable-v6.xml
> >> > > index 6053e3c..30cdaeb 100644
> >> > > --- a/unstable/xdg-shell/xdg-shell-unstable-v6.xml
> >> > > +++ b/unstable/xdg-shell/xdg-shell-unstable-v6.xml
> >> > > @@ -256,7 +256,8 @@
> >> > >        </entry>
> >> > >        <entry name="slide_x" value="1">
> >> > >   <description summary="move along the x axis until unconstrained">
> >> > > -   Slide the surface along the x axis until it is no longer constrained.
> >> > > +   Slide the surface along the x axis within the toplevel surface until it
> >> > > +   is no longer constrained.  
> >> >
> >> > This would break chained popup menus in GTK+. For example a menu chain
> >> > where eventually a menu now completely outside of the toplevel window
> >> > region hits the edge of monitor, and is supposed to slide (see
> >> > screenshot [0]).
> >> >
> >> > So I think we should just limit the way we can slide in relation to the
> >> > parent. Maybe we should rather put the limitations somewhere more
> >> > generic? I.e. a popup can only ever be positioned so that its window
> >> > geometry "touches" (where touches means that there will be no space in
> >> > between) its parent window geometry, or something like that?
> >> >
> >> >
> >> > Jonas
> >> >
> >> >
> >> > [0] https://people.freedesktop.org/~jadahl/menu-slide-outside-of-toplevel.png
> >> >  
> >>
> >> Hm, while I strongly disagree with any application design that requires this level of submenu chaining, I can see why we might need to support at least basic submenu positioning outside the toplevel. I think changing "toplevel" to "parent" in my patch would address that sufficiently?  
> >
> > It sounds like the "sliding within the parent" means the whole child
> > surface must be within the parent, which is not the case. Maybe better
> > with "Slide the surface along the x/y axis until it is no longer
> > constrained or doesn't touch the parent surface anymore." or something.
> >
> >
> > Jonas
> >  
> >>  
> >> > >
> >> > >     First try to slide towards the direction of the gravity on the x axis
> >> > >     until either the edge in the opposite direction of the gravity is
> >> > > @@ -271,7 +272,8 @@
> >> > >        </entry>
> >> > >        <entry name="slide_y" value="2">
> >> > >   <description summary="move along the y axis until unconstrained">
> >> > > -   Slide the surface along the y axis until it is no longer constrained.
> >> > > +   Slide the surface along the y axis within the toplevel surface until it
> >> > > +   is no longer constrained.
> >> > >
> >> > >     First try to slide towards the direction of the gravity on the y axis
> >> > >     until either the edge in the opposite direction of the gravity is
> >> > > --
> >> > > 2.5.5
> >> > >
> >> > > _______________________________________________
> >> > > wayland-devel mailing list
> >> > > wayland-devel at lists.freedesktop.org
> >> > > https://lists.freedesktop.org/mailman/listinfo/wayland-devel  
> >>  
> > _______________________________________________
> > wayland-devel mailing list
> > wayland-devel at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/wayland-devel  

This is a good suggestion. I'll send a new patch which makes a statement about popups being at least adjacent to the parent in some way.