extension/lib/scrollable-elements.coffee

   1 ###
   2 # Copyright Simon Lydell 2015.
   3 #
   4 # This file is part of VimFx.
   5 #
   6 # VimFx is free software: you can redistribute it and/or modify
   7 # it under the terms of the GNU General Public License as published by
   8 # the Free Software Foundation, either version 3 of the License, or
   9 # (at your option) any later version.
  10 #
  11 # VimFx is distributed in the hope that it will be useful,
  12 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 # GNU General Public License for more details.
  15 #
  16 # You should have received a copy of the GNU General Public License
  17 # along with VimFx.  If not, see <http://www.gnu.org/licenses/>.
  18 ###
  19
  20 # This file contains an abstraction for keeping track of scrollable elements,
  21 # automatically keeping the largest scrollable element up-to-date. It stops
  22 # tracking elements that are removed from the DOM, or whose containg frame is
  23 # removed.
  24
  25 utils = require('./utils')
  26
  27 class ScrollableElements
  28   constructor: (@window) ->
  29     @elements = new Set()
  30     @largest  = null
  31
  32   has: (element) -> @elements.has(element)
  33
  34   add: (element) ->
  35     @elements.add(element)
  36     utils.onRemoved(@window, element, @delete.bind(this, element))
  37
  38     if not @largest or utils.area(element) > utils.area(@largest)
  39       @largest = element
  40
  41   delete: (element) =>
  42     @elements.delete(element)
  43     @updateLargest() if @largest == element
  44
  45   reject: (fn) ->
  46     @elements.forEach((element) => @elements.delete(element) if fn(element))
  47     @updateLargest()
  48
  49   updateLargest: ->
  50     @largest = null
  51
  52     # Find a new largest scrollable element (if there are any left).
  53     largestArea = -1
  54     @elements.forEach((element) =>
  55       area = utils.area(element)
  56       if area > largestArea
  57         @largest = element
  58         largestArea = area
  59     )
  60
  61 module.exports = ScrollableElements