[xmonad] my proposal for a Xinerama safe PerWorkspace

[Brent Yorgey]

On Tue, Feb 26, 2008 at 9:27 PM, Spencer Janssen <sjanssen at cse.unl.edu>
wrote:

> On Fri, Feb 22, 2008 at 07:12:31PM +0100, Andrea Rossato wrote:
> > Hi,
> >
> > this is my proposal for a Xinerama safe PerWorkspace.
> >
> > It includes a new LayoutClass method:
> >
> > runLayout :: Workspace WorkspaceId (layout a) a -> Rectangle -> X ([(a,
> Rectangle)], Maybe (layout a))
> >
> > This is just some code moved around:
> >
> > Fri Feb 22 18:58:15 CET 2008  Andrea Rossato <andrea.rossato at unibz.it>
> >   * runLayout is now a LayoutClass method and takes the Workspace and
> the screen Rectangle
> >     M ./XMonad/Core.hs -7 +7
> >     M ./XMonad/Operations.hs -5 +5
> >
> >
> > This is the patch to PerWorkspace:
> >
> > Fri Feb 22 18:59:54 CET 2008  Andrea Rossato <andrea.rossato at unibz.it>
> >   * PerWorkspace: reimplemented using runLayout
> >   This way we have a Xinerama safe PerWorkspace and the emptyLayout
> >   method for free.
> >     M ./XMonad/Layout/PerWorkspace.hs -73 +27
> >
> > Some lines were left there just because I'm lazy....;)
> >
> > Cheers,
> > Andrea
> >
>
> I'm not sure that I'm comfortable with this style of extension.  Consider
> the
> existing pureLayout/doLayout functions in the layout class.   Outside
> consumers
> of the API can really only use doLayout, because pureLayout often has the
> garbage default implementation.  Here we're just adding another layer,
> meaning
> that layout combinators and such can't safely use doLayout anymore, they
> must
> be updated to use runLayout.  It just seems like this style of API just
> isn't
> very nice.
>

Don, what do you think? Anyone else?

To summarize: Andrea's patch moves the 'runLayout' function into the
LayoutClass, changing it to take an entire workspace on which to run the
layout as input, rather than a layout and a stack.  The default
implementation simply extracts the layout and stack from the workspace, and
calls 'doLayout' or 'emptyLayout' as appropriate, but other instances of
LayoutClass (for example, PerWorkspace) are free to override this behavior.
In the case of PerWorkspace, of course, the workspace tag is used.

This provides an elegant solution for PerWorkspace; however, as Spencer
points out, it does mean that most instances of LayoutClass (especially
those that implement layout combinators of some sort) must be changed to use
runLayout instead of doLayout/emptyLayout (note Andrea has already done this
I think), and it will become even more unclear to people writing a
LayoutClass instance which methods they can/should override.

If the consensus is not to apply this, then I will go ahead and push my
other PerWorkspace solution (using the startupHook and special "you are
here" messages).

-Brent
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