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textview.go
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textview.go
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package tk
import (
"sync"
"src.elv.sh/pkg/cli/term"
"src.elv.sh/pkg/ui"
"src.elv.sh/pkg/wcwidth"
)
// TextView is a Widget for displaying text, with support for vertical
// scrolling.
//
// NOTE: This widget now always crops long lines. In future it should support
// wrapping and horizontal scrolling.
type TextView interface {
Widget
// ScrollBy scrolls the widget by the given delta. Positive values scroll
// down, and negative values scroll up.
ScrollBy(delta int)
// MutateState mutates the state.
MutateState(f func(*TextViewState))
// CopyState returns a copy of the State.
CopyState() TextViewState
}
// TextViewSpec specifies the configuration and initial state for a Widget.
type TextViewSpec struct {
// Key bindings.
Bindings Bindings
// If true, a vertical scrollbar will be shown when there are more lines
// that can be displayed, and the widget responds to Up and Down keys.
Scrollable bool
// State. Specifies the initial state if used in New.
State TextViewState
}
// TextViewState keeps mutable state of TextView.
type TextViewState struct {
Lines []string
First int
}
type textView struct {
// Mutex for synchronizing access to the state.
StateMutex sync.RWMutex
TextViewSpec
}
// NewTextView builds a TextView from the given spec.
func NewTextView(spec TextViewSpec) TextView {
if spec.Bindings == nil {
spec.Bindings = DummyBindings{}
}
return &textView{TextViewSpec: spec}
}
func (w *textView) Render(width, height int) *term.Buffer {
lines, first := w.getStateForRender(height)
needScrollbar := w.Scrollable && (first > 0 || first+height < len(lines))
textWidth := width
if needScrollbar {
textWidth--
}
bb := term.NewBufferBuilder(textWidth)
for i := first; i < first+height && i < len(lines); i++ {
if i > first {
bb.Newline()
}
bb.Write(wcwidth.Trim(lines[i], textWidth))
}
buf := bb.Buffer()
if needScrollbar {
scrollbar := VScrollbar{
Total: len(lines), Low: first, High: first + height}
buf.ExtendRight(scrollbar.Render(1, height))
}
return buf
}
func (w *textView) MaxHeight(width, height int) int {
return len(w.CopyState().Lines)
}
func (w *textView) getStateForRender(height int) (lines []string, first int) {
w.MutateState(func(s *TextViewState) {
if s.First > len(s.Lines)-height && len(s.Lines)-height >= 0 {
s.First = len(s.Lines) - height
}
lines, first = s.Lines, s.First
})
return
}
func (w *textView) Handle(event term.Event) bool {
if w.Bindings.Handle(w, event) {
return true
}
if w.Scrollable {
switch event {
case term.K(ui.Up):
w.ScrollBy(-1)
return true
case term.K(ui.Down):
w.ScrollBy(1)
return true
}
}
return false
}
func (w *textView) ScrollBy(delta int) {
w.MutateState(func(s *TextViewState) {
s.First += delta
if s.First < 0 {
s.First = 0
}
if s.First >= len(s.Lines) {
s.First = len(s.Lines) - 1
}
})
}
func (w *textView) MutateState(f func(*TextViewState)) {
w.StateMutex.Lock()
defer w.StateMutex.Unlock()
f(&w.State)
}
// CopyState returns a copy of the State while r-locking the StateMutex.
func (w *textView) CopyState() TextViewState {
w.StateMutex.RLock()
defer w.StateMutex.RUnlock()
return w.State
}