This is a convenience module in order to have less import noise. It
re-exports the following:
a) Commonly used modules in full (Data.Foldable, Data.Applicative, and
so on); though only those that play nicely with each other, so that
XMonad.Prelude can be imported unqualified without any problems.
This prevents things like `Prelude.(.)` and `Control.Category.(.)`
fighting with each other.
b) Helper functions that don't necessarily fit in any other module;
e.g., the often used abbreviation `fi = fromIntegral`.
Provide boring-aware versions of the 'siftUp' and 'siftDown' functions.
Since these actions never affect the position of boring windows, they
work well with layouts that decide which windows are visible/hidden
based on stack position, such as LimitWindows.
The effect is the same, but this seems to express the intent more
clearly, and it will make it easier to factor out the shared behavior
with skipBoringSwapUp.
Provide boring-aware versions of 'swapUp' and 'swapDown'.
Note that 'iterate f x' produces a list whose zeroth element is
'x' prior to any application of 'f'. The 'focusUp' and 'focusDown'
operations reject this iteration by checking in the filter predicate
that the focus actually changed:
filter ((`notElem` W.focus st:bs) . W.focus)
We can't do that for swaps, since our focus never changes, so we drop
the zeroth iteration prior to any predicate-based filtering.
The filter predicate checks whether the window immediately below the
our focus is boring. If so, we've performed an uninteresting upwards
swap and should continue swapping until we either swap past a window
that is not boring or wrap around the top of the stack.
It's particularly important that we accept the wrapping case regardless
of any boring neighbor, otherwise we risk missing a legitimate
non-boring swap. Consider, for example, the following stack:
focus: A
up: []
down: [B, boringC]
A swapUp yields:
focus: A
up: [boringC, B]
down: []
This should be considered non-boring, since the non-boring windows
swapped order: A B -> B A. If we were to reject it, we'd swap A up past
boringC and up again past B, putting us back where we started.
Put another way, if our focus was at the top of the stack, then all
other windows were necessarily below it. We want a swapUp to place our
focus below the lowest non-boring window. A wrap around to the bottom of
the stack guarantees that is the case.
Despite myLayouts currently being more popular in examples, make
them all myLayout as in man/xmonad.hs to avoid mixing them in the
same module as was done a few places, leading to confusion for some users.
The Replace and Merge messages are added to support layouts sending a list of
windows that should be skipped over. The sources are tagged by a string key, so
it is possible though unlikely for different sources of boring windows to
interfere with eachother.
