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listbox.go
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listbox.go
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package tk
import (
"strings"
"sync"
"src.elv.sh/pkg/cli/term"
"src.elv.sh/pkg/ui"
)
// ListBox is a list for displaying and selecting from a list of items.
type ListBox interface {
Widget
// CopyState returns a copy of the state.
CopyState() ListBoxState
// Reset resets the state of the widget with the given items and index of
// the selected item. It triggers the OnSelect callback if the index is
// valid.
Reset(it Items, selected int)
// Select changes the selection by calling f with the current state, and
// using the return value as the new selection index. It triggers the
// OnSelect callback if the selected index has changed and is valid.
Select(f func(ListBoxState) int)
// Accept accepts the currently selected item.
Accept()
}
// ListBoxSpec specifies the configuration and initial state for ListBox.
type ListBoxSpec struct {
// Key bindings.
Bindings Bindings
// A placeholder to show when there are no items.
Placeholder ui.Text
// A function to call when the selected item has changed.
OnSelect func(it Items, i int)
// A function called on the accept event.
OnAccept func(it Items, i int)
// Whether the listbox should be rendered in a horizontal layout. Note that
// in the horizontal layout, items must have only one line.
Horizontal bool
// The minimal amount of space to reserve for left and right sides of each
// entry.
Padding int
// If true, the left padding of each item will be styled the same as the
// first segment of the item, and the right spacing and padding will be
// styled the same as the last segment of the item.
ExtendStyle bool
// State. When used in [NewListBox], this field specifies the initial state.
State ListBoxState
}
type listBox struct {
// Mutex for synchronizing access to the state.
StateMutex sync.RWMutex
// Configuration and state.
ListBoxSpec
}
// NewListBox creates a new ListBox from the given spec.
func NewListBox(spec ListBoxSpec) ListBox {
if spec.Bindings == nil {
spec.Bindings = DummyBindings{}
}
if spec.OnAccept == nil {
spec.OnAccept = func(Items, int) {}
}
if spec.OnSelect == nil {
spec.OnSelect = func(Items, int) {}
} else {
s := spec.State
if s.Items != nil && 0 <= s.Selected && s.Selected < s.Items.Len() {
spec.OnSelect(s.Items, s.Selected)
}
}
return &listBox{ListBoxSpec: spec}
}
var stylingForSelected = ui.Inverse
func (w *listBox) Render(width, height int) *term.Buffer {
if w.Horizontal {
return w.renderHorizontal(width, height)
}
return w.renderVertical(width, height)
}
func (w *listBox) MaxHeight(width, height int) int {
s := w.CopyState()
if s.Items == nil || s.Items.Len() == 0 {
return 0
}
if w.Horizontal {
_, h, scrollbar := getHorizontalWindow(s, w.Padding, width, height)
if scrollbar {
return h + 1
}
return h
}
h := 0
for i := 0; i < s.Items.Len(); i++ {
h += s.Items.Show(i).CountLines()
if h >= height {
return height
}
}
return h
}
const listBoxColGap = 2
func (w *listBox) renderHorizontal(width, height int) *term.Buffer {
var state ListBoxState
var colHeight int
w.mutate(func(s *ListBoxState) {
if s.Items == nil || s.Items.Len() == 0 {
s.First = 0
} else {
s.First, s.ContentHeight, _ = getHorizontalWindow(*s, w.Padding, width, height)
colHeight = s.ContentHeight
}
state = *s
})
if state.Items == nil || state.Items.Len() == 0 {
return Label{Content: w.Placeholder}.Render(width, height)
}
items, selected, first := state.Items, state.Selected, state.First
n := items.Len()
buf := term.NewBuffer(0)
remainedWidth := width
hasCropped := false
last := first
for i := first; i < n; i += colHeight {
selectedRow := -1
// Render the column starting from i.
col := make([]ui.Text, 0, colHeight)
for j := i; j < i+colHeight && j < n; j++ {
last = j
item := items.Show(j)
if j == selected {
selectedRow = j - i
}
col = append(col, item)
}
colWidth := maxWidth(items, w.Padding, i, i+colHeight)
if colWidth > remainedWidth {
colWidth = remainedWidth
hasCropped = true
}
colBuf := croppedLines{
lines: col, padding: w.Padding,
selectFrom: selectedRow, selectTo: selectedRow + 1,
extendStyle: w.ExtendStyle}.Render(colWidth, colHeight)
buf.ExtendRight(colBuf)
remainedWidth -= colWidth
if remainedWidth <= listBoxColGap {
break
}
remainedWidth -= listBoxColGap
buf.Width += listBoxColGap
}
// We may not have used all the width required; force buffer width.
buf.Width = width
if colHeight < height && (first != 0 || last != n-1 || hasCropped) {
scrollbar := HScrollbar{Total: n, Low: first, High: last + 1}
buf.Extend(scrollbar.Render(width, 1), false)
}
return buf
}
func (w *listBox) renderVertical(width, height int) *term.Buffer {
var state ListBoxState
var firstCrop int
w.mutate(func(s *ListBoxState) {
if s.Items == nil || s.Items.Len() == 0 {
s.First = 0
} else {
s.First, firstCrop = getVerticalWindow(*s, height)
}
s.ContentHeight = height
state = *s
})
if state.Items == nil || state.Items.Len() == 0 {
return Label{Content: w.Placeholder}.Render(width, height)
}
items, selected, first := state.Items, state.Selected, state.First
n := items.Len()
allLines := []ui.Text{}
hasCropped := firstCrop > 0
var i, selectFrom, selectTo int
for i = first; i < n && len(allLines) < height; i++ {
item := items.Show(i)
lines := item.SplitByRune('\n')
if i == first {
lines = lines[firstCrop:]
}
if i == selected {
selectFrom, selectTo = len(allLines), len(allLines)+len(lines)
}
// TODO: Optionally, add underlines to the last line as a visual
// separator between adjacent entries.
if len(allLines)+len(lines) > height {
lines = lines[:len(allLines)+len(lines)-height]
hasCropped = true
}
allLines = append(allLines, lines...)
}
var rd Renderer = croppedLines{
lines: allLines, padding: w.Padding,
selectFrom: selectFrom, selectTo: selectTo, extendStyle: w.ExtendStyle}
if first > 0 || i < n || hasCropped {
rd = VScrollbarContainer{
Content: rd,
Scrollbar: VScrollbar{Total: n, Low: first, High: i},
}
}
return rd.Render(width, height)
}
type croppedLines struct {
lines []ui.Text
padding int
selectFrom int
selectTo int
extendStyle bool
}
func (c croppedLines) Render(width, height int) *term.Buffer {
bb := term.NewBufferBuilder(width)
leftSpacing := ui.T(strings.Repeat(" ", c.padding))
rightSpacing := ui.T(strings.Repeat(" ", width-c.padding))
for i, line := range c.lines {
if i > 0 {
bb.Newline()
}
selected := c.selectFrom <= i && i < c.selectTo
extendStyle := c.extendStyle && len(line) > 0
left := leftSpacing.Clone()
if extendStyle && len(left) > 0 {
left[0].Style = line[0].Style
}
acc := ui.Concat(left, line.TrimWcwidth(width-2*c.padding))
if extendStyle || selected {
right := rightSpacing.Clone()
if extendStyle {
right[0].Style = line[len(line)-1].Style
}
acc = ui.Concat(acc, right).TrimWcwidth(width)
}
if selected {
acc = ui.StyleText(acc, stylingForSelected)
}
bb.WriteStyled(acc)
}
return bb.Buffer()
}
func (w *listBox) Handle(event term.Event) bool {
if w.Bindings.Handle(w, event) {
return true
}
switch event {
case term.K(ui.Up):
w.Select(Prev)
return true
case term.K(ui.Down):
w.Select(Next)
return true
case term.K(ui.Enter):
w.Accept()
return true
}
return false
}
func (w *listBox) CopyState() ListBoxState {
w.StateMutex.RLock()
defer w.StateMutex.RUnlock()
return w.State
}
func (w *listBox) Reset(it Items, selected int) {
w.mutate(func(s *ListBoxState) { *s = ListBoxState{Items: it, Selected: selected} })
if 0 <= selected && selected < it.Len() {
w.OnSelect(it, selected)
}
}
func (w *listBox) Select(f func(ListBoxState) int) {
var it Items
var oldSelected, selected int
w.mutate(func(s *ListBoxState) {
oldSelected, it = s.Selected, s.Items
selected = f(*s)
s.Selected = selected
})
if selected != oldSelected && 0 <= selected && selected < it.Len() {
w.OnSelect(it, selected)
}
}
// Prev moves the selection to the previous item, or does nothing if the
// first item is currently selected. It is a suitable as an argument to
// [ListBox.Select].
func Prev(s ListBoxState) int {
return fixIndex(s.Selected-1, s.Items.Len())
}
// PrevPage moves the selection to the item one page before. It is only
// meaningful in vertical layout and suitable as an argument to
// [ListBox.Select].
//
// TODO(xiaq): This does not correctly with multi-line items.
func PrevPage(s ListBoxState) int {
return fixIndex(s.Selected-s.ContentHeight, s.Items.Len())
}
// Next moves the selection to the previous item, or does nothing if the
// last item is currently selected. It is a suitable as an argument to
// [ListBox.Select].
func Next(s ListBoxState) int {
return fixIndex(s.Selected+1, s.Items.Len())
}
// NextPage moves the selection to the item one page after. It is only
// meaningful in vertical layout and suitable as an argument to
// [ListBox.Select].
//
// TODO(xiaq): This does not correctly with multi-line items.
func NextPage(s ListBoxState) int {
return fixIndex(s.Selected+s.ContentHeight, s.Items.Len())
}
// PrevWrap moves the selection to the previous item, or to the last item if
// the first item is currently selected. It is a suitable as an argument to
// [ListBox.Select].
func PrevWrap(s ListBoxState) int {
selected, n := s.Selected, s.Items.Len()
switch {
case selected >= n:
return n - 1
case selected <= 0:
return n - 1
default:
return selected - 1
}
}
// NextWrap moves the selection to the previous item, or to the first item
// if the last item is currently selected. It is a suitable as an argument to
// [ListBox.Select].
func NextWrap(s ListBoxState) int {
selected, n := s.Selected, s.Items.Len()
switch {
case selected >= n-1:
return 0
case selected < 0:
return 0
default:
return selected + 1
}
}
// Left moves the selection to the item to the left. It is only meaningful in
// horizontal layout and suitable as an argument to [ListBox.Select].
func Left(s ListBoxState) int {
return horizontal(s.Selected, s.Items.Len(), -s.ContentHeight)
}
// Right moves the selection to the item to the right. It is only meaningful in
// horizontal layout and suitable as an argument to [ListBox.Select].
func Right(s ListBoxState) int {
return horizontal(s.Selected, s.Items.Len(), s.ContentHeight)
}
func horizontal(selected, n, d int) int {
selected = fixIndex(selected, n)
newSelected := selected + d
if newSelected < 0 || newSelected >= n {
return selected
}
return newSelected
}
func fixIndex(i, n int) int {
switch {
case i < 0:
return 0
case i >= n:
return n - 1
default:
return i
}
}
func (w *listBox) Accept() {
state := w.CopyState()
if 0 <= state.Selected && state.Selected < state.Items.Len() {
w.OnAccept(state.Items, state.Selected)
}
}
func (w *listBox) mutate(f func(s *ListBoxState)) {
w.StateMutex.Lock()
defer w.StateMutex.Unlock()
f(&w.State)
}