[PATCH wayland 1/2 v2] protocol: Add resize from center flag.

[Scott Moreau]

On Mon, Nov 19, 2012 at 1:39 PM, Kristian Høgsberg <hoegsberg at gmail.com>wrote:

> On Mon, Nov 19, 2012 at 12:10:09PM -0700, Scott Moreau wrote:
> > On Mon, Nov 19, 2012 at 11:36 AM, Bill Spitzak <spitzak at gmail.com>
> wrote:
> >
> > > Scott Moreau wrote:
> > >
> > >  Because resize-from-center depends on knowing what edge was actually
> > >> clicked on, setting both left and right bits simultaneously means
> that both
> > >> left and right cases will be hit, and whichever sets the offset last,
> wins.
> > >>
> > >
> > > You should be able to tell "which" edge by what side of the original
> > > center the mouse is on. So if the user grabs the top-right corner and
> then
> > > moves the mouse so that it is to the lower-left of the center, they
> are now
> > > dragging the bottom-left corner. The few things I have that do
> > > resize-from-center (drawing programs are all I can find) work exactly
> this
> > > way.
> >
> >
> > My point is that we're not confined to a single byte of data to store
> edge
> > flags. We have plenty of room to store additional flags. I agree that it
> > would be a nice way to structure the data, I don't think it warrants the
> > additional code required to support it. By dedicating a single bit to
> > 'resize opposing edges', you're avoiding all the code that would have to
> be
> > in place to detect the grabbed edge, regardless if you store it in a
> > different edge mask or compute the pointer position against the original
> > center, later.
>
> Ah, right I see the problem now.  How about we leave it entirely to
> the compositor to implement resize from center behavior when shift is
> clicked?  No changes to the protocol, just make the compositor do
> resize from center when shift is held down.


The reason is because in order for this to work, it requires client
support. The client must know when resize-from-center is happening on the
compositor side, to calculate the x/y offsets accordingly.


>  Metacity has a similar
> move/resize behavior where it restricts the position/sizes to only
> those that align with other edges when shift is held down.  This works
> regardless whether the resize was started from clicking the frame,
> alt-left/middleclick or a _NET_WM_MOVERESIZE message.
>
> Kristian
>


Scott
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