Update textinput for multi-char (IME) input in Bubble Tea master

Note that to do this we've replaced the blink timer with a context.

.github/workflows/build.yml

@@ -4,14 +4,14 @@ jobs:
   test:
     strategy:
       matrix:
-        go-version: [1.13.x, 1.14.x, 1.15.x]
+        go-version: [~1.13, ^1]
         os: [ubuntu-latest, macos-latest, windows-latest]
     runs-on: ${{ matrix.os }}
     env:
       GO111MODULE: "on"
     steps:
       - name: Install Go
-        uses: actions/setup-go@v1
+        uses: actions/setup-go@v2
         with:
           go-version: ${{ matrix.go-version }}
 
@@ -26,12 +26,3 @@ jobs:
 
       - name: Test
         run: go test ./...
-
-      - name: Coverage
-        env:
-          COVERALLS_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-        run: |
-          go test -race -covermode atomic -coverprofile=profile.cov ./...
-          GO111MODULE=off go get github.com/mattn/goveralls
-          $(go env GOPATH)/bin/goveralls -coverprofile=profile.cov -service=github
-        if: matrix.go-version == '1.15.x' && matrix.os == 'ubuntu-latest'

.github/workflows/coverage.yml

@@ -0,0 +1,28 @@
+name: coverage
+on: [push, pull_request]
+
+jobs:
+  coverage:
+    strategy:
+      matrix:
+        go-version: [^1]
+        os: [ubuntu-latest]
+    runs-on: ${{ matrix.os }}
+    env:
+      GO111MODULE: "on"
+    steps:
+      - name: Install Go
+        uses: actions/setup-go@v2
+        with:
+          go-version: ${{ matrix.go-version }}
+
+      - name: Checkout code
+        uses: actions/checkout@v2
+
+      - name: Coverage
+        env:
+          COVERALLS_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          go test -race -covermode atomic -coverprofile=profile.cov ./...
+          GO111MODULE=off go get github.com/mattn/goveralls
+          $(go env GOPATH)/bin/goveralls -coverprofile=profile.cov -service=github

README.md

@@ -1,9 +1,10 @@
 Bubbles
 =======
 
+[![Latest Release](https://img.shields.io/github/release/charmbracelet/bubbles.svg)](https://github.com/charmbracelet/bubbles/releases)
+[![GoDoc](https://godoc.org/github.com/golang/gddo?status.svg)](https://pkg.go.dev/github.com/charmbracelet/bubbles)
 [![Build Status](https://github.com/charmbracelet/bubbles/workflows/build/badge.svg)](https://github.com/charmbracelet/bubbles/actions)
 [![Go ReportCard](http://goreportcard.com/badge/charmbracelet/bubbles)](http://goreportcard.com/report/charmbracelet/bubbles)
-[![GoDoc](https://godoc.org/github.com/golang/gddo?status.svg)](https://pkg.go.dev/github.com/charmbracelet/bubbles)
 
 Some components for [Bubble Tea](https://github.com/charmbracelet/bubbletea) applications.
 
@@ -32,7 +33,7 @@ pasting, in-place scrolling when the value exceeds the width of the element and
 the common, and many customization options.
 
 * [Example code, one field](https://github.com/charmbracelet/tea/tree/master/examples/textinput/main.go)
-* [Example code, many fields](https://github.com/charmbracelet/tea/tree/master/examples/textinput/main.go)
+* [Example code, many fields](https://github.com/charmbracelet/tea/tree/master/examples/textinputs/main.go)
 
 
 ## Paginator

go.mod

@@ -4,7 +4,7 @@ go 1.13
 
 require (
 	github.com/atotto/clipboard v0.1.2
-	github.com/charmbracelet/bubbletea v0.12.1
+	github.com/charmbracelet/bubbletea v0.12.2-0.20201101135743-116a0cfb8f37
 	github.com/mattn/go-runewidth v0.0.9
 	github.com/muesli/termenv v0.7.4
 	golang.org/x/crypto v0.0.0-20201016220609-9e8e0b390897 // indirect

go.sum

@@ -1,7 +1,7 @@
 github.com/atotto/clipboard v0.1.2 h1:YZCtFu5Ie8qX2VmVTBnrqLSiU9XOWwqNRmdT3gIQzbY=
 github.com/atotto/clipboard v0.1.2/go.mod h1:ZY9tmq7sm5xIbd9bOK4onWV4S6X0u6GY7Vn0Yu86PYI=
-github.com/charmbracelet/bubbletea v0.12.1 h1:t21pkG2IDBRduPbt2J64Dx5yt8yIidAkXwhhrc11SzY=
-github.com/charmbracelet/bubbletea v0.12.1/go.mod h1:3gZkYELUOiEUOp0bTInkxguucy/xRbGSOcbMs1geLxg=
+github.com/charmbracelet/bubbletea v0.12.2-0.20201101135743-116a0cfb8f37 h1:BQLGyhKVE19a9XdNYcsnYlO9XHPlOVHIWM7+mmS014k=
+github.com/charmbracelet/bubbletea v0.12.2-0.20201101135743-116a0cfb8f37/go.mod h1:3gZkYELUOiEUOp0bTInkxguucy/xRbGSOcbMs1geLxg=
 github.com/containerd/console v1.0.1 h1:u7SFAJyRqWcG6ogaMAx3KjSTy1e3hT9QxqX7Jco7dRc=
 github.com/containerd/console v1.0.1/go.mod h1:XUsP6YE/mKtz6bxc+I8UiKKTP04qjQL4qcS3XoQ5xkw=
 github.com/google/goterm v0.0.0-20190703233501-fc88cf888a3f h1:5CjVwnuUcp5adK4gmY6i72gpVFVnZDP2h5TmPScB6u4=

paginator/paginator.go

@@ -40,8 +40,8 @@ type Model struct {
 // used for other things beyond navigating sets. Note that it both returns the
 // number of total pages and alters the model.
 func (m *Model) SetTotalPages(items int) int {
-	if items == 0 {
-		return 0
+	if items < 1 {
+		return m.TotalPages
 	}
 	n := items / m.PerPage
 	if items%m.PerPage > 0 {

textinput/textinput.go

@@ -1,6 +1,7 @@
 package textinput
 
 import (
+	"context"
 	"strings"
 	"time"
 	"unicode"
@@ -11,7 +12,21 @@ import (
 	"github.com/muesli/termenv"
 )
 
-const defaultBlinkSpeed = time.Millisecond * 600
+const defaultBlinkSpeed = time.Millisecond * 530
+
+// color is a helper for returning colors.
+var color func(s string) termenv.Color = termenv.ColorProfile().Color
+
+// blinkMsg and blinkCanceled are used to manage cursor blinking.
+type blinkMsg struct{}
+type blinkCanceled struct{}
+
+// Messages for clipboard events.
+type pasteMsg string
+type pasteErrMsg struct{ error }
+
+// EchoMode sets the input behavior of the text input field.
+type EchoMode int
 
 const (
 	// EchoNormal displays text as is. This is the default behavior.
@@ -28,29 +43,33 @@ const (
 	// EchoOnEdit
 )
 
-// EchoMode sets the input behavior of the text input field.
-type EchoMode int
+// blinkCtx manages cursor blinking.
+type blinkCtx struct {
+	ctx    context.Context
+	cancel context.CancelFunc
+}
 
-var (
-	// color is a helper for returning colors.
-	color func(s string) termenv.Color = termenv.ColorProfile().Color
+type cursorMode int
+
+const (
+	cursorBlink = iota
+	cursorStatic
+	cursorHide
 )
 
 // Model is the Bubble Tea model for this text input element.
 type Model struct {
 	Err error
 
+	// General settings
 	Prompt           string
 	Placeholder      string
-
 	Cursor           string
 	BlinkSpeed       time.Duration
-
 	TextColor        string
 	BackgroundColor  string
 	PlaceholderColor string
 	CursorColor      string
-
 	EchoMode         EchoMode
 	EchoCharacter    rune
 
@@ -80,6 +99,36 @@ type Model struct {
 	// overflowing.
 	offset      int
 	offsetRight int
+
+	// Used to manage cursor blink
+	blinkCtx *blinkCtx
+
+	// cursorMode determines the behavior of the cursor
+	cursorMode cursorMode
+}
+
+// NewModel creates a new model with default settings.
+func NewModel() Model {
+	return Model{
+		Prompt:           "> ",
+		Placeholder:      "",
+		BlinkSpeed:       defaultBlinkSpeed,
+		TextColor:        "",
+		PlaceholderColor: "240",
+		CursorColor:      "",
+		EchoCharacter:    '*',
+		CharLimit:        0,
+
+		value:      nil,
+		focus:      false,
+		blink:      true,
+		pos:        0,
+		cursorMode: cursorBlink,
+
+		blinkCtx: &blinkCtx{
+			ctx: context.Background(),
+		},
+	}
 }
 
 // SetValue sets the value of the text input.
@@ -91,7 +140,7 @@ func (m *Model) SetValue(s string) {
 		m.value = runes
 	}
 	if m.pos > len(m.value) {
-		m.pos = len(m.value)
+		m.SetCursor(len(m.value))
 	}
 	m.handleOverflow()
 }
@@ -103,21 +152,28 @@ func (m Model) Value() string {
 
 // SetCursor start moves the cursor to the given position. If the position is
 // out of bounds the cursor will be moved to the start or end accordingly.
-func (m *Model) SetCursor(pos int) {
+// Returns whether or nor the cursor timer should be reset.
+func (m *Model) SetCursor(pos int) bool {
 	m.pos = clamp(pos, 0, len(m.value))
 	m.handleOverflow()
+
+	// Show the cursor unless it's been explicitly hidden
+	m.blink = m.cursorMode == cursorHide
+
+	// Reset cursor blink if necessary
+	return m.cursorMode == cursorBlink
 }
 
-// CursorStart moves the cursor to the start of the field.
-func (m *Model) CursorStart() {
-	m.pos = 0
-	m.handleOverflow()
+// CursorStart moves the cursor to the start of the field. Returns whether or
+// not the curosr blink should be reset.
+func (m *Model) CursorStart() bool {
+	return m.SetCursor(0)
 }
 
-// CursorEnd moves the cursor to the end of the field.
-func (m *Model) CursorEnd() {
-	m.pos = len(m.value)
-	m.handleOverflow()
+// CursorEnd moves the cursor to the end of the field. Returns whether or not
+// the cursor blink should be reset.
+func (m *Model) CursorEnd() bool {
+	return m.SetCursor(len(m.value))
 }
 
 // Focused returns the focus state on the model.
@@ -128,7 +184,7 @@ func (m Model) Focused() bool {
 // Focus sets the focus state on the model.
 func (m *Model) Focus() {
 	m.focus = true
-	m.blink = false
+	m.blink = m.cursorMode == cursorHide // show the cursor unless we've explicitly hidden it
 }
 
 // Blur removes the focus state on the model.
@@ -137,22 +193,22 @@ func (m *Model) Blur() {
 	m.blink = true
 }
 
-// Reset sets the input to its default state with no input.
-func (m *Model) Reset() {
+// Reset sets the input to its default state with no input. Returns whether
+// or not the cursor blink should reset.
+func (m *Model) Reset() bool {
 	m.value = nil
-	m.pos = 0
-	m.blink = false
+	return m.SetCursor(0)
 }
 
-// Paste pastes the contents of the clipboard into the text area (if supported).
-func (m *Model) Paste() {
-	pasteString, err := clipboard.ReadAll()
-	if err != nil {
-		m.Err = err
-	}
-	paste := []rune(pasteString)
+// handle a clipboard paste event, if supported. Returns whether or not the
+// cursor blink should be reset.
+func (m *Model) handlePaste(v string) (blink bool) {
+	paste := []rune(v)
 
-	availSpace := m.CharLimit - len(m.value)
+	var availSpace int
+	if m.CharLimit > 0 {
+		availSpace = m.CharLimit - len(m.value)
+	}
 
 	// If the char limit's been reached cancel
 	if m.CharLimit > 0 && availSpace <= 0 {
@@ -161,7 +217,7 @@ func (m *Model) Paste() {
 
 	// If there's not enough space to paste the whole thing cut the pasted
 	// runes down so they'll fit
-	if availSpace < len(paste) {
+	if m.CharLimit > 0 && availSpace < len(paste) {
 		paste = paste[:len(paste)-availSpace]
 	}
 
@@ -174,15 +230,20 @@ func (m *Model) Paste() {
 	// Insert pasted runes
 	for _, r := range paste {
 		head = append(head, r)
-		availSpace--
 		m.pos++
-		if m.CharLimit > 0 && availSpace <= 0 {
+		if m.CharLimit > 0 {
+			availSpace--
+			if availSpace <= 0 {
 				break
 			}
 		}
+	}
 
 	// Put it all back together
 	m.value = append(head, tail...)
+
+	// Reset blink state if necessary and run overflow checks
+	return m.SetCursor(m.pos)
 }
 
 // If a max width is defined, perform some logic to treat the visible area
@@ -250,7 +311,76 @@ func (m *Model) colorPlaceholder(s string) string {
 		String()
 }
 
-func (m *Model) wordLeft() {
+// deleteWordLeft deletes the word left to the cursor. Returns whether or not
+// the cursor blink should be reset.
+func (m *Model) deleteWordLeft() (blink bool) {
+	if m.pos == 0 || len(m.value) == 0 {
+		return
+	}
+
+	i := m.pos
+	blink = m.SetCursor(m.pos - 1)
+	for unicode.IsSpace(m.value[m.pos]) {
+		// ignore series of whitespace before cursor
+		blink = m.SetCursor(m.pos - 1)
+	}
+
+	for m.pos > 0 {
+		if !unicode.IsSpace(m.value[m.pos]) {
+			blink = m.SetCursor(m.pos - 1)
+		} else {
+			if m.pos > 0 {
+				// keep the previous space
+				blink = m.SetCursor(m.pos + 1)
+			}
+			break
+		}
+	}
+
+	if i > len(m.value) {
+		m.value = m.value[:m.pos]
+	} else {
+		m.value = append(m.value[:m.pos], m.value[i:]...)
+	}
+
+	return
+}
+
+// deleteWordRight deletes the word right to the cursor. Returns whether or not
+// the cursor blink should be reset.
+func (m *Model) deleteWordRight() (blink bool) {
+	if m.pos >= len(m.value) || len(m.value) == 0 {
+		return
+	}
+
+	i := m.pos
+	blink = m.SetCursor(m.pos + 1)
+	for unicode.IsSpace(m.value[m.pos]) {
+		// ignore series of whitespace after cursor
+		blink = m.SetCursor(m.pos + 1)
+	}
+
+	for m.pos < len(m.value) {
+		if !unicode.IsSpace(m.value[m.pos]) {
+			blink = m.SetCursor(m.pos + 1)
+		} else {
+			break
+		}
+	}
+
+	if m.pos > len(m.value) {
+		m.value = m.value[:i]
+	} else {
+		m.value = append(m.value[:i], m.value[m.pos:]...)
+	}
+	blink = m.SetCursor(i)
+
+	return
+}
+
+// wordLeft moves the cursor one word to the left. Returns whether or not the
+// cursor blink should be reset.
+func (m *Model) wordLeft() (blink bool) {
 	if m.pos == 0 || len(m.value) == 0 {
 		return
 	}
@@ -259,7 +389,7 @@ func (m *Model) wordLeft() {
 
 	for i >= 0 {
 		if unicode.IsSpace(m.value[i]) {
-			m.pos--
+			blink = m.SetCursor(m.pos - 1)
 			i--
 		} else {
 			break
@@ -268,15 +398,19 @@ func (m *Model) wordLeft() {
 
 	for i >= 0 {
 		if !unicode.IsSpace(m.value[i]) {
-			m.pos--
+			blink = m.SetCursor(m.pos - 1)
 			i--
 		} else {
 			break
 		}
 	}
+
+	return
 }
 
-func (m *Model) wordRight() {
+// wordRight moves the cursor one word to the right. Returns whether or not the
+// cursor blink should be reset.
+func (m *Model) wordRight() (blink bool) {
 	if m.pos >= len(m.value) || len(m.value) == 0 {
 		return
 	}
@@ -285,7 +419,7 @@ func (m *Model) wordRight() {
 
 	for i < len(m.value) {
 		if unicode.IsSpace(m.value[i]) {
-			m.pos++
+			blink = m.SetCursor(m.pos + 1)
 			i++
 		} else {
 			break
@@ -294,12 +428,14 @@ func (m *Model) wordRight() {
 
 	for i < len(m.value) {
 		if !unicode.IsSpace(m.value[i]) {
-			m.pos++
+			blink = m.SetCursor(m.pos + 1)
 			i++
 		} else {
 			break
 		}
 	}
+
+	return
 }
 
 func (m Model) echoTransform(v string) string {
@@ -314,121 +450,119 @@ func (m Model) echoTransform(v string) string {
 	}
 }
 
-// BlinkMsg is sent when the cursor should alternate it's blinking state.
-type BlinkMsg struct{}
-
-// NewModel creates a new model with default settings.
-func NewModel() Model {
-	return Model{
-		Prompt:      "> ",
-		Placeholder: "",
-
-		BlinkSpeed: defaultBlinkSpeed,
-
-		TextColor:        "",
-		PlaceholderColor: "240",
-		CursorColor:      "",
-
-		EchoCharacter: '*',
-
-		CharLimit: 0,
-
-		value: nil,
-		focus: false,
-		blink: true,
-		pos:   0,
-	}
-}
-
-// Update is the Tea update loop.
-func Update(msg tea.Msg, m Model) (Model, tea.Cmd) {
+// Update is the Bubble Tea update loop.
+func (m Model) Update(msg tea.Msg) (Model, tea.Cmd) {
 	if !m.focus {
 		m.blink = true
 		return m, nil
 	}
 
+	var resetBlink bool
+
 	switch msg := msg.(type) {
 	case tea.KeyMsg:
 		switch msg.Type {
 		case tea.KeyBackspace: // delete character before cursor
+			if msg.Alt {
+				resetBlink = m.deleteWordLeft()
+			} else {
 				if len(m.value) > 0 {
 					m.value = append(m.value[:max(0, m.pos-1)], m.value[m.pos:]...)
 					if m.pos > 0 {
-					m.pos--
+						resetBlink = m.SetCursor(m.pos - 1)
 					}
 				}
-		case tea.KeyLeft:
+			}
+		case tea.KeyLeft, tea.KeyCtrlB:
 			if msg.Alt { // alt+left arrow, back one word
-				m.wordLeft()
+				resetBlink = m.wordLeft()
 				break
 			}
-			if m.pos > 0 {
-				m.pos--
+			if m.pos > 0 { // left arrow, ^F, back one character
+				resetBlink = m.SetCursor(m.pos - 1)
 			}
-		case tea.KeyRight:
+		case tea.KeyRight, tea.KeyCtrlF:
 			if msg.Alt { // alt+right arrow, forward one word
-				m.wordRight()
+				resetBlink = m.wordRight()
 				break
 			}
-			if m.pos < len(m.value) {
-				m.pos++
+			if m.pos < len(m.value) { // right arrow, ^F, forward one word
+				resetBlink = m.SetCursor(m.pos + 1)
 			}
-		case tea.KeyCtrlF: // ^F, forward one character
-			fallthrough
-		case tea.KeyCtrlB: // ^B, back one charcter
-			fallthrough
+		case tea.KeyCtrlW: // ^W, delete word left of cursor
+			resetBlink = m.deleteWordLeft()
 		case tea.KeyHome, tea.KeyCtrlA: // ^A, go to beginning
-			m.CursorStart()
+			resetBlink = m.CursorStart()
 		case tea.KeyDelete, tea.KeyCtrlD: // ^D, delete char under cursor
 			if len(m.value) > 0 && m.pos < len(m.value) {
 				m.value = append(m.value[:m.pos], m.value[m.pos+1:]...)
 			}
 		case tea.KeyCtrlE, tea.KeyEnd: // ^E, go to end
-			m.CursorEnd()
+			resetBlink = m.CursorEnd()
 		case tea.KeyCtrlK: // ^K, kill text after cursor
 			m.value = m.value[:m.pos]
-			m.pos = len(m.value)
+			resetBlink = m.SetCursor(len(m.value))
 		case tea.KeyCtrlU: // ^U, kill text before cursor
 			m.value = m.value[m.pos:]
-			m.pos = 0
+			resetBlink = m.SetCursor(0)
 			m.offset = 0
 		case tea.KeyCtrlV: // ^V paste
-			m.Paste()
-		case tea.KeyRune: // input a regular character
-
-			if msg.Alt {
-				if msg.Rune == 'b' { // alt+b, back one word
-					m.wordLeft()
+			return m, Paste
+		case tea.KeyRunes: // input regular characters
+			if msg.Alt && len(msg.Runes) == 1 {
+				if msg.Runes[0] == 'd' { // alt+d, delete word right of cursor
+					resetBlink = m.deleteWordRight()
 					break
 				}
-				if msg.Rune == 'f' { // alt+f, forward one word
-					m.wordRight()
+				if msg.Runes[0] == 'b' { // alt+b, back one word
+					resetBlink = m.wordLeft()
+					break
+				}
+				if msg.Runes[0] == 'f' { // alt+f, forward one word
+					resetBlink = m.wordRight()
 					break
 				}
 			}
 
 			// Input a regular character
 			if m.CharLimit <= 0 || len(m.value) < m.CharLimit {
-				m.value = append(m.value[:m.pos], append([]rune{msg.Rune}, m.value[m.pos:]...)...)
-				m.pos++
+				m.value = append(m.value[:m.pos], append(msg.Runes, m.value[m.pos:]...)...)
+				resetBlink = m.SetCursor(m.pos + len(msg.Runes))
 			}
 		}
 
-	case BlinkMsg:
+	case blinkMsg:
+		var cmd tea.Cmd
+		if m.cursorMode == cursorBlink {
 			m.blink = !m.blink
-		return m, Blink(m)
+			cmd = m.blinkCmd()
+		}
+		return m, cmd
+
+	case blinkCanceled: // no-op
+		return m, nil
+
+	case pasteMsg:
+		resetBlink = m.handlePaste(string(msg))
+
+	case pasteErrMsg:
+		m.Err = msg
+	}
+
+	var cmd tea.Cmd
+	if resetBlink {
+		cmd = m.blinkCmd()
 	}
 
 	m.handleOverflow()
-
-	return m, nil
+	return m, cmd
 }
 
 // View renders the textinput in its current state.
-func View(m Model) string {
+func (m Model) View() string {
 	// Placeholder text
 	if len(m.value) == 0 && m.Placeholder != "" {
-		return placeholderView(m)
+		return m.placeholderView()
 	}
 
 	value := m.value[m.offset:m.offsetRight]
@@ -436,10 +570,10 @@ func View(m Model) string {
 	v := m.colorText(m.echoTransform(string(value[:pos])))
 
 	if pos < len(value) {
-		v += cursorView(m.echoTransform(string(value[pos])), m)  // cursor and text under it
+		v += m.cursorView(m.echoTransform(string(value[pos])))   // cursor and text under it
 		v += m.colorText(m.echoTransform(string(value[pos+1:]))) // text after cursor
 	} else {
-		v += cursorView(" ", m)
+		v += m.cursorView(" ")
 	}
 
 	// If a max width and background color were set fill the empty spaces with
@@ -459,8 +593,8 @@ func View(m Model) string {
 	return m.Prompt + v
 }
 
-// placeholderView.
-func placeholderView(m Model) string {
+// placeholderView returns the prompt and placeholder view, if any.
+func (m Model) placeholderView() string {
 	var (
 		v string
 		p = m.Placeholder
@@ -468,9 +602,9 @@ func placeholderView(m Model) string {
 
 	// Cursor
 	if m.blink && m.PlaceholderColor != "" {
-		v += cursorView(m.colorPlaceholder(p[:1]), m)
+		v += m.cursorView(m.colorPlaceholder(p[:1]))
 	} else {
-		v += cursorView(p[:1], m)
+		v += m.cursorView(p[:1])
 	}
 
 	// The rest of the placeholder text
@@ -480,29 +614,54 @@ func placeholderView(m Model) string {
 }
 
 // cursorView styles the cursor.
-func cursorView(s string, m Model) string {
+func (m Model) cursorView(v string) string {
 	if m.blink {
 		if m.TextColor != "" || m.BackgroundColor != "" {
-			return termenv.String(s).
+			return termenv.String(v).
 				Foreground(color(m.TextColor)).
 				Background(color(m.BackgroundColor)).
 				String()
 		}
-		return s
+		return v
 	}
-	return termenv.String(s).
+	return termenv.String(v).
 		Foreground(color(m.CursorColor)).
 		Background(color(m.BackgroundColor)).
 		Reverse().
 		String()
 }
 
-// Blink is a command used to time the cursor blinking.
-func Blink(model Model) tea.Cmd {
-	return func() tea.Msg {
-		time.Sleep(model.BlinkSpeed)
-		return BlinkMsg{}
+// blinkCmd is an internal command used to manage cursor blinking.
+func (m Model) blinkCmd() tea.Cmd {
+	if m.blinkCtx != nil && m.blinkCtx.cancel != nil {
+		m.blinkCtx.cancel()
 	}
+
+	ctx, cancel := context.WithTimeout(m.blinkCtx.ctx, m.BlinkSpeed)
+	m.blinkCtx.cancel = cancel
+
+	return func() tea.Msg {
+		defer cancel()
+		<-ctx.Done()
+		if ctx.Err() == context.DeadlineExceeded {
+			return blinkMsg{}
+		}
+		return blinkCanceled{}
+	}
+}
+
+// Blink is a command used to initialize cursor blinking.
+func Blink() tea.Msg {
+	return blinkMsg{}
+}
+
+// Paste is a command for pasting from the clipboard into the text input.
+func Paste() tea.Msg {
+	str, err := clipboard.ReadAll()
+	if err != nil {
+		return pasteErrMsg{err}
+	}
+	return pasteMsg(str)
 }
 
 func clamp(v, low, high int) int {

viewport/viewport.go

@@ -77,7 +77,7 @@ func (m *Model) SetContent(s string) {
 func (m Model) visibleLines() (lines []string) {
 	if len(m.lines) > 0 {
 		top := max(0, m.YOffset)
-		bottom := min(len(m.lines), m.YOffset+m.Height)
+		bottom := clamp(m.YOffset+m.Height, top, len(m.lines))
 		lines = m.lines[top:bottom]
 	}
 	return lines
@@ -125,7 +125,7 @@ func (m *Model) HalfViewDown() (lines []string) {
 
 	if len(m.lines) > 0 {
 		top := max(m.YOffset+m.Height/2, 0)
-		bottom := min(m.YOffset+m.Height, len(m.lines)-1)
+		bottom := clamp(m.YOffset+m.Height, top, len(m.lines)-1)
 		lines = m.lines[top:bottom]
 	}
 
@@ -145,7 +145,7 @@ func (m *Model) HalfViewUp() (lines []string) {
 
 	if len(m.lines) > 0 {
 		top := max(m.YOffset, 0)
-		bottom := min(m.YOffset+m.Height/2, len(m.lines)-1)
+		bottom := clamp(m.YOffset+m.Height/2, top, len(m.lines)-1)
 		lines = m.lines[top:bottom]
 	}
 
@@ -171,7 +171,7 @@ func (m *Model) LineDown(n int) (lines []string) {
 
 	if len(m.lines) > 0 {
 		top := max(m.YOffset+m.Height-n, 0)
-		bottom := min(m.YOffset+m.Height, len(m.lines)-1)
+		bottom := clamp(m.YOffset+m.Height, top, len(m.lines)-1)
 		lines = m.lines[top:bottom]
 	}
 
@@ -193,7 +193,7 @@ func (m *Model) LineUp(n int) (lines []string) {
 
 	if len(m.lines) > 0 {
 		top := max(0, m.YOffset)
-		bottom := min(m.YOffset+n, len(m.lines)-1)
+		bottom := clamp(m.YOffset+n, top, len(m.lines)-1)
 		lines = m.lines[top:bottom]
 	}
 
@@ -210,7 +210,7 @@ func (m *Model) GotoTop() (lines []string) {
 
 	if len(m.lines) > 0 {
 		top := m.YOffset
-		bottom := min(m.YOffset+m.Height, len(m.lines)-1)
+		bottom := clamp(m.YOffset+m.Height, top, len(m.lines)-1)
 		lines = m.lines[top:bottom]
 	}
 
@@ -245,7 +245,7 @@ func Sync(m Model) tea.Cmd {
 	// TODO: we should probably use m.visibleLines() rather than these two
 	// expressions.
 	top := max(m.YOffset, 0)
-	bottom := min(m.YOffset+m.Height, len(m.lines)-1)
+	bottom := clamp(m.YOffset+m.Height, 0, len(m.lines)-1)
 
 	return tea.SyncScrollArea(
 		m.lines[top:bottom],
@@ -376,6 +376,10 @@ func View(m Model) string {
 
 // ETC
 
+func clamp(v, low, high int) int {
+	return min(high, max(low, v))
+}
+
 func min(a, b int) int {
 	if a < b {
 		return a