{-
Bustle.Regions: tracks a series of selectable horizontal stripes
Copyright © 2011–2012 Collabora Ltd.
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
-}
{-# LANGUAGE DeriveFunctor #-}
module Bustle.Regions
(
Stripe(..)
, nonOverlapping
, midpoint
, Regions
, translateRegions
, RegionSelection (..)
, regionSelectionNew
, regionSelectionAppend
, regionSelectionFlatten
, regionSelectionUpdate
, regionSelectionSelect
, regionSelectionUp
, regionSelectionDown
, regionSelectionFirst
, regionSelectionLast
)
where
import Data.Maybe (maybeToList)
import Data.List (sort)
data Stripe = Stripe { stripeTop :: Double
, stripeBottom :: Double
}
deriving
(Show, Eq, Ord)
type Region a = (Stripe, a)
type Regions a = [Region a]
translateRegions :: Double
-> Regions a
-> Regions a
translateRegions y = map (\(s, a) -> (translate s, a))
where
translate (Stripe y1 y2) = Stripe (y1 + y) (y2 + y)
-- A zipper for selected regions. rsBefore is reversed. If rsCurrent is
-- Nothing, the two lists may still both be non-empty (to keep track of roughly
-- where the user's last click was).
data RegionSelection a =
RegionSelection { rsBefore :: Regions a
, rsLastClick :: Double
, rsCurrent :: Maybe (Region a)
, rsAfter :: Regions a
}
deriving
(Show, Eq, Functor)
relativeTo :: Double
-> Stripe
-> Ordering
relativeTo y (Stripe top bottom)
| y < top = LT
| y > bottom = GT
| otherwise = EQ
hits :: Double
-> Stripe
-> Bool
hits y stripe = y `relativeTo` stripe == EQ
nonOverlapping :: [Stripe]
-> Bool
nonOverlapping [] = True
nonOverlapping [_] = True
nonOverlapping (s1:s2:ss) =
stripeBottom s1 <= stripeTop s2 && nonOverlapping (s2:ss)
regionSelectionNew :: Regions a
-> RegionSelection a
regionSelectionNew rs
| sorted /= map fst rs = error "regionSelectionNew: unsorted regions"
| not (nonOverlapping sorted) = error "regionSelectionNew: overlapping regions"
| otherwise = RegionSelection [] 0 Nothing rs
where
sorted = sort (map fst rs)
regionSelectionFlatten :: RegionSelection a
-> Regions a
regionSelectionFlatten rs =
reverse (rsBefore rs) ++ maybeToList (rsCurrent rs) ++ rsAfter rs
regionSelectionAppend :: Regions a
-> RegionSelection a
-> RegionSelection a
regionSelectionAppend [] old = old
regionSelectionAppend regions@((newFirst, _):_) old =
case rsCurrent (regionSelectionLast old) of
Nothing -> new
Just (oldLast, _) ->
if oldLast < newFirst && nonOverlapping [oldLast, newFirst]
then old { rsAfter = rsAfter old ++ rsAfter new }
else error "regionSelectionAppend: new regions overlap old regions"
where
new = regionSelectionNew regions
regionSelectionUpdate :: Double
-> RegionSelection a
-> RegionSelection a
regionSelectionUpdate y rs = rs' { rsLastClick = y }
where
rs' = case rsCurrent rs of
Just r@(s, _)
| y `hits` s -> rs
| otherwise -> doSearch (rsBefore rs) (r:rsAfter rs)
Nothing -> doSearch (rsBefore rs) (rsAfter rs)
doSearch bs as =
if y <= rsLastClick rs
then
let (as', result, bs') =
searchy y (\y' s -> y' <= stripeBottom s) as bs
in rs { rsBefore = bs'
, rsCurrent = result
, rsAfter = as'
}
else
let (bs', result, as') =
searchy y (\y' s -> y' >= stripeTop s) bs as
in rs { rsBefore = bs'
, rsCurrent = result
, rsAfter = as'
}
invert :: RegionSelection a
-> RegionSelection a
invert rs = rs { rsBefore = rsAfter rs, rsAfter = rsBefore rs }
midpoint :: Stripe -> Double
midpoint (Stripe top bottom) = (top + bottom) / 2
regionSelectionUp :: RegionSelection a
-> RegionSelection a
regionSelectionUp rs@(RegionSelection before _lastClick current after) =
case before of
[] -> rs
(b:bs) -> RegionSelection bs
(midpoint (fst b))
(Just b)
(maybeToList current ++ after)
regionSelectionDown :: RegionSelection a
-> RegionSelection a
regionSelectionDown = invert . regionSelectionUp . invert
regionSelectionFirst :: RegionSelection a
-> RegionSelection a
regionSelectionFirst rs =
case reverse (rsBefore rs) ++ maybeToList (rsCurrent rs) ++ rsAfter rs of
[] -> rs
(first:others) -> RegionSelection []
(midpoint (fst first))
(Just first)
others
regionSelectionLast :: RegionSelection a
-> RegionSelection a
regionSelectionLast = invert . regionSelectionFirst . invert
searchy :: Double
-> (Double -> Stripe -> Bool)
-> Regions a
-> Regions a
-> (Regions a, Maybe (Region a), Regions a)
searchy y worthContinuing = go
where
go befores [] = (befores, Nothing, [])
go befores afters@(a:as)
| y `hits` fst a = (befores, Just a, as)
| worthContinuing y (fst a) = go (a:befores) as
| otherwise = (befores, Nothing, afters)
regionSelectionSelect :: Eq a
=> a
-> RegionSelection a
-> RegionSelection a
regionSelectionSelect x rs
| fmap snd (rsCurrent rs) == Just x = rs
| otherwise = case break ((== x) . snd) (rsBefore rs) of
(ys, z:zs) -> RegionSelection { rsBefore = zs
, rsCurrent = Just z
, rsLastClick = midpoint (fst z)
, rsAfter = reverse ys ++ rsAfter rs
}
(_, []) -> case break ((== x) . snd) (rsAfter rs) of
(ys, z:zs) -> RegionSelection { rsBefore = rsBefore rs ++ reverse ys
, rsCurrent = Just z
, rsLastClick = midpoint (fst z)
, rsAfter = zs
}
(_, []) -> rs