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$ = jQuery
class ScrollHandler
constructor: (tree_widget) ->
@tree_widget = tree_widget
@previous_top = -1
@is_initialized = false
_initScrollParent: ->
getParentWithOverflow = =>
css_values = ['overflow', 'overflow-y']
hasOverFlow = (el) ->
for css_value in css_values
if $.css(el, css_value) in ['auto', 'scroll']
return true
return false
if hasOverFlow(@tree_widget.$el[0])
return @tree_widget.$el
for el in @tree_widget.$el.parents()
if hasOverFlow(el)
return $(el)
return null
setDocumentAsScrollParent = =>
@scroll_parent_top = 0
@$scroll_parent = null
if @tree_widget.$el.css('position') == 'fixed'
setDocumentAsScrollParent()
$scroll_parent = getParentWithOverflow()
if $scroll_parent and $scroll_parent.length and $scroll_parent[0].tagName != 'HTML'
@$scroll_parent = $scroll_parent
@scroll_parent_top = @$scroll_parent.offset().top
else
setDocumentAsScrollParent()
@is_initialized = true
_ensureInit: ->
if not @is_initialized
@_initScrollParent()
checkScrolling: ->
@_ensureInit()
hovered_area = @tree_widget.dnd_handler.hovered_area
if hovered_area and hovered_area.top != @previous_top
@previous_top = hovered_area.top
if @$scroll_parent
@_handleScrollingWithScrollParent(hovered_area)
else
@_handleScrollingWithDocument(hovered_area)
_handleScrollingWithScrollParent: (area) ->
distance_bottom = @scroll_parent_top + @$scroll_parent[0].offsetHeight - area.bottom
if distance_bottom < 20
@$scroll_parent[0].scrollTop += 20
@tree_widget.refreshHitAreas()
@previous_top = -1
else if (area.top - @scroll_parent_top) < 20
@$scroll_parent[0].scrollTop -= 20
@tree_widget.refreshHitAreas()
@previous_top = -1
_handleScrollingWithDocument: (area) ->
distance_top = area.top - $(document).scrollTop()
if distance_top < 20
$(document).scrollTop($(document).scrollTop() - 20)
else if $(window).height() - (area.bottom - $(document).scrollTop()) < 20
$(document).scrollTop($(document).scrollTop() + 20)
scrollTo: (top) ->
@_ensureInit()
if @$scroll_parent
@$scroll_parent[0].scrollTop = top
else
tree_top = @tree_widget.$el.offset().top
$(document).scrollTop(top + tree_top)
isScrolledIntoView: (element) ->
@_ensureInit()
$element = $(element)
if @$scroll_parent
view_top = 0
view_bottom = @$scroll_parent.height()
element_top = $element.offset().top - @scroll_parent_top
element_bottom = element_top + $element.height()
else
view_top = $(window).scrollTop()
view_bottom = view_top + $(window).height()
element_top = $element.offset().top
element_bottom = element_top + $element.height()
return (element_bottom <= view_bottom) and (element_top >= view_top)
module.exports = ScrollHandler
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