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package app
// Scrollable implements vertical scrolling
type Scrollable struct {
scroll int
height int
elems int
}
func (s *Scrollable) Scroll() int {
return s.scroll
}
func (s *Scrollable) PercentVisible() float64 {
if s.elems <= 0 {
return 1.0
}
return float64(s.height) / float64(s.elems)
}
func (s *Scrollable) PercentScrolled() float64 {
if s.elems <= 0 {
return 1.0
}
return float64(s.scroll) / float64(s.elems)
}
func (s *Scrollable) NeedScrollbar() bool {
needScrollbar := true
if s.PercentVisible() >= 1.0 {
needScrollbar = false
}
return needScrollbar
}
func (s *Scrollable) UpdateScroller(height, elems int) {
s.height = height
s.elems = elems
}
func (s *Scrollable) EnsureScroll(selectingIdx int) {
if selectingIdx < 0 {
return
}
maxScroll := s.elems - s.height
if maxScroll < 0 {
maxScroll = 0
}
if selectingIdx >= s.scroll && selectingIdx < s.scroll+s.height {
if s.scroll > maxScroll {
s.scroll = maxScroll
}
return
}
if selectingIdx >= s.scroll+s.height {
s.scroll = selectingIdx - s.height + 1
} else if selectingIdx < s.scroll {
s.scroll = selectingIdx
}
if s.scroll > maxScroll {
s.scroll = maxScroll
}
}
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