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

[Scott Moreau]

On Fri, Nov 16, 2012 at 5:32 PM, Kristian Høgsberg <hoegsberg at gmail.com>wrote:

> On Thu, Nov 15, 2012 at 01:38:54PM -0700, Scott Moreau wrote:
> > On Thu, Nov 15, 2012 at 1:02 PM, Scott Moreau <oreaus at gmail.com> wrote:
> >
> > >
> > >
> > > On Thu, Nov 15, 2012 at 12:57 PM, Bill Spitzak <spitzak at gmail.com>
> wrote:
> > >
> > >> A scheme I have seen is to use 15 (ie all 4 edge flags or'd) for
> > >> center-resize. This makes it possible to add 6 (left | right) for
> "center
> > >> resize horizontally" and 3 (top | bottom) for "center resize
> vertically".
> > >>
> > >> The only values from 1-15 that have no meaning are when 3 edges are
> > >> selected.
> > >
> > >
> > > Now that you mention it, I believe I have seen this used somewhere too
> and
> > > it makes sense. As a side note, the algorithm is always the same for
> > > resize-from-center regardless if it's horizontal, vertical or both.
> > >
> >
> > I was tinkering with this idea and I remember trying it and why it wont
> fit
> > nicely here. We're using resize_from_center as a separate single bit flag
> > because it's actually resize state. Trying to make it have the meaning
> you
> > described while maintaining this real-time behavior would require much
> more
> > invasive changes. The edge flags would have to be stored separately
> because
> > we have to remember what edges were set before toggling
> resize-from-center.
> > It's simpler all around to have a single separate flag than try to mix
> > everything together and try to decipher how to handle it later.
>
> Hm, I like the idea of making left|right mean resize horizontally from
> center, and trigger that on shift click side of window, and simiarly
> for vertical resize from center on shift click top or bottom edge.
> Shift click any corner is resize from center for all sides.
>
> We can just add 'left_right', 'top_bttom' and 'all' enums that are the
> bitwise or of left and right etc, and all being 15.  Why would that
> not work?  Seem like a pretty elegant approach.
>
> Kristian
>
>
Hi Kristian,

This concept is an interesting one with more to it than meets the eye. I
will try to explain my observations.


There's at least two behaviors that can be implemented here: 1) Set
resize-from-center edge flags when the grab is initiated. 2) Set
resize-from-center flags dynamically. With 1), you will have to end up
creating a new binding, for mod+shift+button0 so you'll end up with two
separate resize bindings. With 2), which is what this patch does, you can
toggle resize-from-center while still holding a grab, with shift key.

Regarding the flags: With 1), having top_bottom=3, left_right=12 and all=15
would work. You'd still end up with two resize bindings. With 2), this
would not work without making a bit of a mess. Since the flags are
combined, there would be no way to know what the original or current flags
should be. For instance, you start resizing from top(1), press shift and
now you're resizing from top_bottom(3) but when shift is released, there's
no way of knowing what flags to set without storing the original edge(s)
separately. Using 0x10 for 'all' allows to preserve the original edges
storing the optional flag for resize-from-center separately. I also wrote
some preliminary documentation for edges here
http://lists.freedesktop.org/archives/wayland-devel/2012-November/006164.htmlI
like thereal-time toggling bahavior of this feature and would like to
use
it if feasible.


Scott
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