brick-0.4: src/Brick/Widgets/Core.hs
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE TupleSections #-}
-- | This module provides the core widget combinators and rendering
-- routines. Everything this library does is in terms of these basic
-- primitives.
module Brick.Widgets.Core
( -- * Basic rendering primitives
emptyWidget
, raw
, txt
, str
, fill
-- * Padding
, padLeft
, padRight
, padTop
, padBottom
, padLeftRight
, padTopBottom
, padAll
-- * Box layout
, (<=>)
, (<+>)
, hBox
, vBox
-- * Limits
, hLimit
, vLimit
-- * Attribute management
, withDefAttr
, withAttr
, forceAttr
, updateAttrMap
-- * Border style management
, withBorderStyle
-- * Cursor placement
, showCursor
-- * Translation
, translateBy
-- * Cropping
, cropLeftBy
, cropRightBy
, cropTopBy
, cropBottomBy
-- * Scrollable viewports
, viewport
, visible
, visibleRegion
, unsafeLookupViewport
-- ** Adding offsets to cursor positions and visibility requests
, addResultOffset
-- ** Cropping results
, cropToContext
)
where
import Control.Applicative
import Control.Lens ((^.), (.~), (&), (%~), to, _1, _2, each, to, ix, Lens')
import Control.Monad ((>=>),when)
import Control.Monad.Trans.State.Lazy
import Control.Monad.Trans.Reader
import Control.Monad.Trans.Class (lift)
import qualified Data.Text as T
import Data.Default
import Data.Monoid ((<>), mempty)
import qualified Data.Map as M
import qualified Data.Function as DF
import Data.List (sortBy, partition)
import qualified Graphics.Vty as V
import Control.DeepSeq
import Brick.Types
import Brick.Types.Internal
import Brick.Widgets.Border.Style
import Brick.Util (clOffset, clamp)
import Brick.AttrMap
import Brick.Widgets.Internal
-- | When rendering the specified widget, use the specified border style
-- for any border rendering.
withBorderStyle :: BorderStyle -> Widget -> Widget
withBorderStyle bs p = Widget (hSize p) (vSize p) $ withReaderT (& ctxBorderStyleL .~ bs) (render p)
-- | The empty widget.
emptyWidget :: Widget
emptyWidget = raw V.emptyImage
-- | Add an offset to all cursor locations and visbility requests
-- in the specified rendering result. This function is critical for
-- maintaining correctness in the rendering results as they are
-- processed successively by box layouts and other wrapping combinators,
-- since calls to this function result in converting from widget-local
-- coordinates to (ultimately) terminal-global ones so they can be used
-- by other combinators. You should call this any time you render
-- something and then translate it or otherwise offset it from its
-- original origin.
addResultOffset :: Location -> Result -> Result
addResultOffset off = addCursorOffset off . addVisibilityOffset off
addVisibilityOffset :: Location -> Result -> Result
addVisibilityOffset off r = r & visibilityRequestsL.each.vrPositionL %~ (off <>)
addCursorOffset :: Location -> Result -> Result
addCursorOffset off r =
let onlyVisible = filter isVisible
isVisible l = l^.columnL >= 0 && l^.rowL >= 0
in r & cursorsL %~ (\cs -> onlyVisible $ (`clOffset` off) <$> cs)
unrestricted :: Int
unrestricted = 100000
-- | Build a widget from a 'String'. Breaks newlines up and space-pads
-- short lines out to the length of the longest line.
str :: String -> Widget
str s =
Widget Fixed Fixed $ do
c <- getContext
let theLines = fixEmpty <$> (dropUnused . lines) s
fixEmpty [] = " "
fixEmpty l = l
dropUnused l = take (availWidth c) <$> take (availHeight c) l
case force theLines of
[] -> return def
[one] -> return $ def & imageL .~ (V.string (c^.attrL) one)
multiple ->
let maxLength = maximum $ length <$> multiple
lineImgs = lineImg <$> multiple
lineImg lStr = V.string (c^.attrL) (lStr ++ replicate (maxLength - length lStr) ' ')
in return $ def & imageL .~ (V.vertCat lineImgs)
-- | Build a widget from a one-line 'T.Text' value. Behaves the same as
-- 'str'.
txt :: T.Text -> Widget
txt = str . T.unpack
-- | Pad the specified widget on the left. If max padding is used, this
-- grows greedily horizontally; otherwise it defers to the padded
-- widget.
padLeft :: Padding -> Widget -> Widget
padLeft padding p =
let (f, sz) = case padding of
Max -> (id, Greedy)
Pad i -> (hLimit i, hSize p)
in Widget sz (vSize p) $ do
result <- render p
render $ (f $ vLimit (result^.imageL.to V.imageHeight) $ fill ' ') <+>
(Widget Fixed Fixed $ return result)
-- | Pad the specified widget on the right. If max padding is used,
-- this grows greedily horizontally; otherwise it defers to the padded
-- widget.
padRight :: Padding -> Widget -> Widget
padRight padding p =
let (f, sz) = case padding of
Max -> (id, Greedy)
Pad i -> (hLimit i, hSize p)
in Widget sz (vSize p) $ do
result <- render p
render $ (Widget Fixed Fixed $ return result) <+>
(f $ vLimit (result^.imageL.to V.imageHeight) $ fill ' ')
-- | Pad the specified widget on the top. If max padding is used, this
-- grows greedily vertically; otherwise it defers to the padded widget.
padTop :: Padding -> Widget -> Widget
padTop padding p =
let (f, sz) = case padding of
Max -> (id, Greedy)
Pad i -> (vLimit i, vSize p)
in Widget (hSize p) sz $ do
result <- render p
render $ (f $ hLimit (result^.imageL.to V.imageWidth) $ fill ' ') <=>
(Widget Fixed Fixed $ return result)
-- | Pad the specified widget on the bottom. If max padding is used,
-- this grows greedily vertically; otherwise it defers to the padded
-- widget.
padBottom :: Padding -> Widget -> Widget
padBottom padding p =
let (f, sz) = case padding of
Max -> (id, Greedy)
Pad i -> (vLimit i, vSize p)
in Widget (hSize p) sz $ do
result <- render p
render $ (Widget Fixed Fixed $ return result) <=>
(f $ hLimit (result^.imageL.to V.imageWidth) $ fill ' ')
-- | Pad a widget on the left and right. Defers to the padded widget for
-- growth policy.
padLeftRight :: Int -> Widget -> Widget
padLeftRight c w = padLeft (Pad c) $ padRight (Pad c) w
-- | Pad a widget on the top and bottom. Defers to the padded widget for
-- growth policy.
padTopBottom :: Int -> Widget -> Widget
padTopBottom r w = padTop (Pad r) $ padBottom (Pad r) w
-- | Pad a widget on all sides. Defers to the padded widget for growth
-- policy.
padAll :: Int -> Widget -> Widget
padAll v w = padLeftRight v $ padTopBottom v w
-- | Fill all available space with the specified character. Grows both
-- horizontally and vertically.
fill :: Char -> Widget
fill ch =
Widget Greedy Greedy $ do
c <- getContext
return $ def & imageL .~ (V.charFill (c^.attrL) ch (c^.availWidthL) (c^.availHeightL))
-- | Vertical box layout: put the specified widgets one above the other
-- in the specified order (uppermost first). Defers growth policies to
-- the growth policies of the contained widgets (if any are greedy, so
-- is the box).
vBox :: [Widget] -> Widget
vBox [] = emptyWidget
vBox pairs = renderBox vBoxRenderer pairs
-- | Horizontal box layout: put the specified widgets next to each other
-- in the specified order (leftmost first). Defers growth policies to
-- the growth policies of the contained widgets (if any are greedy, so
-- is the box).
hBox :: [Widget] -> Widget
hBox [] = emptyWidget
hBox pairs = renderBox hBoxRenderer pairs
-- | The process of rendering widgets in a box layout is exactly the
-- same except for the dimension under consideration (width vs. height),
-- in which case all of the same operations that consider one dimension
-- in the layout algorithm need to be switched to consider the other.
-- Because of this we fill a BoxRenderer with all of the functions
-- needed to consider the "primary" dimension (e.g. vertical if the
-- box layout is vertical) as well as the "secondary" dimension (e.g.
-- horizontal if the box layout is vertical). Doing this permits us to
-- have one implementation for box layout and parameterizing on the
-- orientation of all of the operations.
data BoxRenderer =
BoxRenderer { contextPrimary :: Lens' Context Int
, contextSecondary :: Lens' Context Int
, imagePrimary :: V.Image -> Int
, imageSecondary :: V.Image -> Int
, limitPrimary :: Int -> Widget -> Widget
, limitSecondary :: Int -> Widget -> Widget
, primaryWidgetSize :: Widget -> Size
, concatenatePrimary :: [V.Image] -> V.Image
, locationFromOffset :: Int -> Location
, padImageSecondary :: Int -> V.Image -> V.Attr -> V.Image
}
vBoxRenderer :: BoxRenderer
vBoxRenderer =
BoxRenderer { contextPrimary = availHeightL
, contextSecondary = availWidthL
, imagePrimary = V.imageHeight
, imageSecondary = V.imageWidth
, limitPrimary = vLimit
, limitSecondary = hLimit
, primaryWidgetSize = vSize
, concatenatePrimary = V.vertCat
, locationFromOffset = Location . (0 ,)
, padImageSecondary = \amt img a ->
let p = V.charFill a ' ' amt (V.imageHeight img)
in V.horizCat [img, p]
}
hBoxRenderer :: BoxRenderer
hBoxRenderer =
BoxRenderer { contextPrimary = availWidthL
, contextSecondary = availHeightL
, imagePrimary = V.imageWidth
, imageSecondary = V.imageHeight
, limitPrimary = hLimit
, limitSecondary = vLimit
, primaryWidgetSize = hSize
, concatenatePrimary = V.horizCat
, locationFromOffset = Location . (, 0)
, padImageSecondary = \amt img a ->
let p = V.charFill a ' ' (V.imageWidth img) amt
in V.vertCat [img, p]
}
-- | Render a series of widgets in a box layout in the order given.
--
-- The growth policy of a box layout is the most unrestricted of the
-- growth policies of the widgets it contains, so to determine the hSize
-- and vSize of the box we just take the maximum (using the Ord instance
-- for Size) of all of the widgets to be rendered in the box.
--
-- Then the box layout algorithm proceeds as follows. We'll use
-- the vertical case to concretely describe the algorithm, but the
-- horizontal case can be envisioned just by exchanging all
-- "vertical"/"horizontal" and "rows"/"columns", etc., in the
-- description.
--
-- The growth policies of the child widgets determine the order in which
-- they are rendered, i.e., the order in which space in the box is
-- allocated to widgets as the algorithm proceeds. This is because order
-- matters: if we render greedy widgets first, there will be no space
-- left for non-greedy ones.
--
-- So we render all widgets with size 'Fixed' in the vertical dimension
-- first. Each is rendered with as much room as the overall box has, but
-- we assume that they will not be greedy and use it all. If they do,
-- maybe it's because the terminal is small and there just isn't enough
-- room to render everything.
--
-- Then the remaining height is distributed evenly amongst all remaining
-- (greedy) widgets and they are rendered in sub-boxes that are as high
-- as this even slice of rows and as wide as the box is permitted to be.
-- We only do this step at all if rendering the non-greedy widgets left
-- us any space, i.e., if there were any rows left.
--
-- After rendering the non-greedy and then greedy widgets, their images
-- are sorted so that they are stored in the order the original widgets
-- were given. All cursor locations and visibility requests in each
-- sub-widget are translated according to the position of the sub-widget
-- in the box.
--
-- All images are padded to be as wide as the widest sub-widget to
-- prevent attribute over-runs. Without this step the attribute used by
-- a sub-widget may continue on in an undesirable fashion until it hits
-- something with a different attribute. To prevent this and to behave
-- in the least surprising way, we pad the image on the right with
-- whitespace using the context's current attribute.
--
-- Finally, the padded images are concatenated together vertically and
-- returned along with the translated cursor positions and visibility
-- requests.
renderBox :: BoxRenderer -> [Widget] -> Widget
renderBox br ws =
Widget (maximum $ hSize <$> ws) (maximum $ vSize <$> ws) $ do
c <- getContext
let pairsIndexed = zip [(0::Int)..] ws
(his, lows) = partition (\p -> (primaryWidgetSize br $ snd p) == Fixed) pairsIndexed
renderedHis <- mapM (\(i, prim) -> (i,) <$> render prim) his
renderedLows <- case lows of
[] -> return []
ls -> do
let remainingPrimary = c^.(contextPrimary br) - (sum $ (^._2.imageL.(to $ imagePrimary br)) <$> renderedHis)
primaryPerLow = remainingPrimary `div` length ls
padFirst = remainingPrimary - (primaryPerLow * length ls)
secondaryPerLow = c^.(contextSecondary br)
primaries = replicate (length ls) primaryPerLow & ix 0 %~ (+ padFirst)
let renderLow ((i, prim), pri) =
(i,) <$> (render $ limitPrimary br pri
$ limitSecondary br secondaryPerLow
$ cropToContext prim)
if remainingPrimary > 0 then mapM renderLow (zip ls primaries) else return []
let rendered = sortBy (compare `DF.on` fst) $ renderedHis ++ renderedLows
allResults = snd <$> rendered
allImages = (^.imageL) <$> allResults
allPrimaries = imagePrimary br <$> allImages
allTranslatedResults = (flip map) (zip [0..] allResults) $ \(i, result) ->
let off = locationFromOffset br offPrimary
offPrimary = sum $ take i allPrimaries
in addResultOffset off result
-- Determine the secondary dimension value to pad to. In a
-- vertical box we want all images to be the same width to
-- avoid attribute over-runs or blank spaces with the wrong
-- attribute. In a horizontal box we want all images to have
-- the same height for the same reason.
maxSecondary = maximum $ imageSecondary br <$> allImages
padImage img = padImageSecondary br (maxSecondary - imageSecondary br img) img (c^.attrL)
paddedImages = padImage <$> allImages
cropResultToContext $ Result (concatenatePrimary br paddedImages)
(concat $ cursors <$> allTranslatedResults)
(concat $ visibilityRequests <$> allTranslatedResults)
-- | Limit the space available to the specified widget to the specified
-- number of columns. This is important for constraining the horizontal
-- growth of otherwise-greedy widgets. This is non-greedy horizontally
-- and defers to the limited widget vertically.
hLimit :: Int -> Widget -> Widget
hLimit w p =
Widget Fixed (vSize p) $
withReaderT (& availWidthL .~ w) $ render $ cropToContext p
-- | Limit the space available to the specified widget to the specified
-- number of rows. This is important for constraining the vertical
-- growth of otherwise-greedy widgets. This is non-greedy vertically and
-- defers to the limited widget horizontally.
vLimit :: Int -> Widget -> Widget
vLimit h p =
Widget (hSize p) Fixed $
withReaderT (& availHeightL .~ h) $ render $ cropToContext p
-- | When drawing the specified widget, set the current attribute used
-- for drawing to the one with the specified name. Note that the widget
-- may use further calls to 'withAttr' to override this; if you really
-- want to prevent that, use 'forceAttr'. Attributes used this way still
-- get merged hierarchically and still fall back to the attribute map's
-- default attribute. If you want to change the default attribute, use
-- 'withDefAttr'.
withAttr :: AttrName -> Widget -> Widget
withAttr an p =
Widget (hSize p) (vSize p) $
withReaderT (& ctxAttrNameL .~ an) (render p)
-- | Update the attribute map while rendering the specified widget: set
-- its new default attribute to the one that we get by looking up the
-- specified attribute name in the map.
withDefAttr :: AttrName -> Widget -> Widget
withDefAttr an p =
Widget (hSize p) (vSize p) $ do
c <- getContext
withReaderT (& ctxAttrMapL %~ (setDefault (attrMapLookup an (c^.ctxAttrMapL)))) (render p)
-- | When rendering the specified widget, update the attribute map with
-- the specified transformation.
updateAttrMap :: (AttrMap -> AttrMap) -> Widget -> Widget
updateAttrMap f p =
Widget (hSize p) (vSize p) $
withReaderT (& ctxAttrMapL %~ f) (render p)
-- | When rendering the specified widget, force all attribute lookups
-- in the attribute map to use the value currently assigned to the
-- specified attribute name.
forceAttr :: AttrName -> Widget -> Widget
forceAttr an p =
Widget (hSize p) (vSize p) $ do
c <- getContext
withReaderT (& ctxAttrMapL .~ (forceAttrMap (attrMapLookup an (c^.ctxAttrMapL)))) (render p)
-- | Build a widget directly from a raw Vty image.
raw :: V.Image -> Widget
raw img = Widget Fixed Fixed $ return $ def & imageL .~ img
-- | Translate the specified widget by the specified offset amount.
-- Defers to the translated width for growth policy.
translateBy :: Location -> Widget -> Widget
translateBy off p =
Widget (hSize p) (vSize p) $ do
result <- render p
return $ addResultOffset off
$ result & imageL %~ (V.translate (off^.columnL) (off^.rowL))
-- | Crop the specified widget on the left by the specified number of
-- columns. Defers to the translated width for growth policy.
cropLeftBy :: Int -> Widget -> Widget
cropLeftBy cols p =
Widget (hSize p) (vSize p) $ do
result <- render p
let amt = V.imageWidth (result^.imageL) - cols
cropped img = if amt < 0 then V.emptyImage else V.cropLeft amt img
return $ addResultOffset (Location (-1 * cols, 0))
$ result & imageL %~ cropped
-- | Crop the specified widget on the right by the specified number of
-- columns. Defers to the translated width for growth policy.
cropRightBy :: Int -> Widget -> Widget
cropRightBy cols p =
Widget (hSize p) (vSize p) $ do
result <- render p
let amt = V.imageWidth (result^.imageL) - cols
cropped img = if amt < 0 then V.emptyImage else V.cropRight amt img
return $ result & imageL %~ cropped
-- | Crop the specified widget on the top by the specified number of
-- rows. Defers to the translated width for growth policy.
cropTopBy :: Int -> Widget -> Widget
cropTopBy rows p =
Widget (hSize p) (vSize p) $ do
result <- render p
let amt = V.imageHeight (result^.imageL) - rows
cropped img = if amt < 0 then V.emptyImage else V.cropTop amt img
return $ addResultOffset (Location (0, -1 * rows))
$ result & imageL %~ cropped
-- | Crop the specified widget on the bottom by the specified number of
-- rows. Defers to the translated width for growth policy.
cropBottomBy :: Int -> Widget -> Widget
cropBottomBy rows p =
Widget (hSize p) (vSize p) $ do
result <- render p
let amt = V.imageHeight (result^.imageL) - rows
cropped img = if amt < 0 then V.emptyImage else V.cropBottom amt img
return $ result & imageL %~ cropped
-- | When rendering the specified widget, also register a cursor
-- positioning request using the specified name and location.
showCursor :: Name -> Location -> Widget -> Widget
showCursor n cloc p =
Widget (hSize p) (vSize p) $ do
result <- render p
return $ result & cursorsL %~ (CursorLocation cloc (Just n):)
hRelease :: Widget -> Maybe Widget
hRelease p =
case hSize p of
Fixed -> Just $ Widget Greedy (vSize p) $ withReaderT (& availWidthL .~ unrestricted) (render p)
Greedy -> Nothing
vRelease :: Widget -> Maybe Widget
vRelease p =
case vSize p of
Fixed -> Just $ Widget (hSize p) Greedy $ withReaderT (& availHeightL .~ unrestricted) (render p)
Greedy -> Nothing
-- | Render the specified widget in a named viewport with the
-- specified type. This permits widgets to be scrolled without being
-- scrolling-aware. To make the most use of viewports, the specified
-- widget should use the 'visible' combinator to make a "visibility
-- request". This viewport combinator will then translate the resulting
-- rendering to make the requested region visible. In addition, the
-- 'Brick.Main.EventM' monad provides primitives to scroll viewports
-- created by this function if 'visible' is not what you want.
--
-- If a viewport receives more than one visibility request, only the
-- first is honored. If a viewport receives more than one scrolling
-- request from 'Brick.Main.EventM', all are honored in the order in
-- which they are received.
viewport :: Name
-- ^ The name of the viewport (must be unique and stable for
-- reliable behavior)
-> ViewportType
-- ^ The type of viewport (indicates the permitted scrolling
-- direction)
-> Widget
-- ^ The widget to be rendered in the scrollable viewport
-> Widget
viewport vpname typ p =
Widget Greedy Greedy $ do
-- First, update the viewport size.
c <- getContext
let newVp = VP 0 0 newSize
newSize = (c^.availWidthL, c^.availHeightL)
doInsert (Just vp) = Just $ vp & vpSize .~ newSize
doInsert Nothing = Just newVp
lift $ modify (& viewportMapL %~ (M.alter doInsert vpname))
-- Then render the sub-rendering with the rendering layout
-- constraint released (but raise an exception if we are asked to
-- render an infinitely-sized widget in the viewport's scrolling
-- dimension)
let Name vpn = vpname
release = case typ of
Vertical -> vRelease
Horizontal -> hRelease
Both ->vRelease >=> hRelease
released = case release p of
Just w -> w
Nothing -> case typ of
Vertical -> error $ "tried to embed an infinite-height widget in vertical viewport " <> (show vpn)
Horizontal -> error $ "tried to embed an infinite-width widget in horizontal viewport " <> (show vpn)
Both -> error $ "tried to embed an infinite-width or infinite-height widget in 'Both' type viewport " <> (show vpn)
initialResult <- render released
-- If the rendering state includes any scrolling requests for this
-- viewport, apply those
reqs <- lift $ gets $ (^.scrollRequestsL)
let relevantRequests = snd <$> filter (\(n, _) -> n == vpname) reqs
when (not $ null relevantRequests) $ do
Just vp <- lift $ gets $ (^.viewportMapL.to (M.lookup vpname))
let updatedVp = applyRequests relevantRequests vp
applyRequests [] v = v
applyRequests (rq:rqs) v =
case typ of
Horizontal -> scrollTo typ rq (initialResult^.imageL) $ applyRequests rqs v
Vertical -> scrollTo typ rq (initialResult^.imageL) $ applyRequests rqs v
Both -> scrollTo Horizontal rq (initialResult^.imageL) $
scrollTo Vertical rq (initialResult^.imageL) $
applyRequests rqs v
lift $ modify (& viewportMapL %~ (M.insert vpname updatedVp))
return ()
-- If the sub-rendering requested visibility, update the scroll
-- state accordingly
when (not $ null $ initialResult^.visibilityRequestsL) $ do
Just vp <- lift $ gets $ (^.viewportMapL.to (M.lookup vpname))
let rq = head $ initialResult^.visibilityRequestsL
updatedVp = case typ of
Both -> scrollToView Horizontal rq $ scrollToView Vertical rq vp
Horizontal -> scrollToView typ rq vp
Vertical -> scrollToView typ rq vp
lift $ modify (& viewportMapL %~ (M.insert vpname updatedVp))
-- If the size of the rendering changes enough to make the
-- viewport offsets invalid, reset them
Just vp <- lift $ gets $ (^.viewportMapL.to (M.lookup vpname))
let img = initialResult^.imageL
fixTop v = if V.imageHeight img < v^.vpSize._2
then v & vpTop .~ 0
else v
fixLeft v = if V.imageWidth img < v^.vpSize._1
then v & vpLeft .~ 0
else v
updateVp = case typ of
Both -> fixLeft . fixTop
Horizontal -> fixLeft
Vertical -> fixTop
lift $ modify (& viewportMapL %~ (M.insert vpname (updateVp vp)))
-- Get the viewport state now that it has been updated.
Just vpFinal <- lift $ gets (M.lookup vpname . (^.viewportMapL))
-- Then perform a translation of the sub-rendering to fit into the
-- viewport
translated <- render $ translateBy (Location (-1 * vpFinal^.vpLeft, -1 * vpFinal^.vpTop))
$ Widget Fixed Fixed $ return initialResult
-- Return the translated result with the visibility requests
-- discarded
let translatedSize = ( translated^.imageL.to V.imageWidth
, translated^.imageL.to V.imageHeight
)
case translatedSize of
(0, 0) -> return $ translated & imageL .~ (V.charFill (c^.attrL) ' ' (c^.availWidthL) (c^.availHeightL))
& visibilityRequestsL .~ mempty
_ -> render $ cropToContext
$ padBottom Max
$ padRight Max
$ Widget Fixed Fixed $ return $ translated & visibilityRequestsL .~ mempty
-- | Given a name, obtain the viewport for that name by consulting the
-- viewport map in the rendering monad. NOTE! Some care must be taken
-- when calling this function, since it only returns useful values
-- after the viewport in question has been rendered. If you call this
-- function during rendering before a viewport has been rendered, you
-- may get nothing or you may get a stale version of the viewport. This
-- is because viewports are updated during rendering and the one you are
-- interested in may not have been rendered yet. So if you want to use
-- this, be sure you know what you are doing.
unsafeLookupViewport :: Name -> RenderM (Maybe Viewport)
unsafeLookupViewport name = lift $ gets (M.lookup name . (^.viewportMapL))
scrollTo :: ViewportType -> ScrollRequest -> V.Image -> Viewport -> Viewport
scrollTo Both _ _ _ = error "BUG: called scrollTo on viewport type 'Both'"
scrollTo Vertical req img vp = vp & vpTop .~ newVStart
where
newVStart = clamp 0 (V.imageHeight img - vp^.vpSize._2) adjustedAmt
adjustedAmt = case req of
VScrollBy amt -> vp^.vpTop + amt
VScrollPage Up -> vp^.vpTop - vp^.vpSize._2
VScrollPage Down -> vp^.vpTop + vp^.vpSize._2
VScrollToBeginning -> 0
VScrollToEnd -> V.imageHeight img - vp^.vpSize._2
_ -> vp^.vpTop
scrollTo Horizontal req img vp = vp & vpLeft .~ newHStart
where
newHStart = clamp 0 (V.imageWidth img - vp^.vpSize._1) adjustedAmt
adjustedAmt = case req of
HScrollBy amt -> vp^.vpLeft + amt
HScrollPage Up -> vp^.vpLeft - vp^.vpSize._1
HScrollPage Down -> vp^.vpLeft + vp^.vpSize._1
HScrollToBeginning -> 0
HScrollToEnd -> V.imageWidth img - vp^.vpSize._1
_ -> vp^.vpLeft
scrollToView :: ViewportType -> VisibilityRequest -> Viewport -> Viewport
scrollToView Both _ _ = error "BUG: called scrollToView on 'Both' type viewport"
scrollToView Vertical rq vp = vp & vpTop .~ newVStart
where
curStart = vp^.vpTop
curEnd = curStart + vp^.vpSize._2
reqStart = rq^.vrPositionL.rowL
reqEnd = rq^.vrPositionL.rowL + rq^.vrSizeL._2
newVStart :: Int
newVStart = if reqStart < curStart
then reqStart
else if reqStart > curEnd || reqEnd > curEnd
then reqEnd - vp^.vpSize._2
else curStart
scrollToView Horizontal rq vp = vp & vpLeft .~ newHStart
where
curStart = vp^.vpLeft
curEnd = curStart + vp^.vpSize._1
reqStart = rq^.vrPositionL.columnL
reqEnd = rq^.vrPositionL.columnL + rq^.vrSizeL._1
newHStart :: Int
newHStart = if reqStart < curStart
then reqStart
else if reqStart > curEnd || reqEnd > curEnd
then reqEnd - vp^.vpSize._1
else curStart
-- | Request that the specified widget be made visible when it is
-- rendered inside a viewport. This permits widgets (whose sizes and
-- positions cannot be known due to being embedded in arbitrary layouts)
-- to make a request for a parent viewport to locate them and scroll
-- enough to put them in view. This, together with 'viewport', is what
-- makes the text editor and list widgets possible without making them
-- deal with the details of scrolling state management.
--
-- This does nothing if not rendered in a viewport.
visible :: Widget -> Widget
visible p =
Widget (hSize p) (vSize p) $ do
result <- render p
let imageSize = ( result^.imageL.to V.imageWidth
, result^.imageL.to V.imageHeight
)
-- The size of the image to be made visible in a viewport must have
-- non-zero size in both dimensions.
return $ if imageSize^._1 > 0 && imageSize^._2 > 0
then result & visibilityRequestsL %~ (VR (Location (0, 0)) imageSize :)
else result
-- | Similar to 'visible', request that a region (with the specified
-- 'Location' as its origin and 'V.DisplayRegion' as its size) be made
-- visible when it is rendered inside a viewport. The 'Location' is
-- relative to the specified widget's upper-left corner of (0, 0).
--
-- This does nothing if not rendered in a viewport.
visibleRegion :: Location -> V.DisplayRegion -> Widget -> Widget
visibleRegion vrloc sz p =
Widget (hSize p) (vSize p) $ do
result <- render p
-- The size of the image to be made visible in a viewport must have
-- non-zero size in both dimensions.
return $ if sz^._1 > 0 && sz^._2 > 0
then result & visibilityRequestsL %~ (VR vrloc sz :)
else result
-- | Horizontal box layout: put the specified widgets next to each other
-- in the specified order. Defers growth policies to the growth policies
-- of both widgets. This operator is a binary version of 'hBox'.
(<+>) :: Widget
-- ^ Left
-> Widget
-- ^ Right
-> Widget
(<+>) a b = hBox [a, b]
-- | Vertical box layout: put the specified widgets one above the other
-- in the specified order. Defers growth policies to the growth policies
-- of both widgets. This operator is a binary version of 'vBox'.
(<=>) :: Widget
-- ^ Top
-> Widget
-- ^ Bottom
-> Widget
(<=>) a b = vBox [a, b]