Update paginator for bubbletea 0.12.0

README.md

@@ -1,9 +1,79 @@
-# Tea Party
+Bubbles
+=======
 
-Components for [Tea](https://github.com/charmbraclet/tea)
+<p>
+    <a href="https://pkg.go.dev/github.com/charmbracelet/bubbles?tab=doc"><img src="https://godoc.org/github.com/golang/gddo?status.svg" alt="GoDoc"></a>
+    <a href="https://github.com/charmbracelet/bubbles/actions"><img src="https://github.com/charmbracelet/glow/workflows/build/badge.svg" alt="Build Status"></a>
+</p>
+
+Some components for [Bubble Tea](https://github.com/charmbracelet/bubbletea) applications.
+
+These components are used in production in [Glow][glow] and [Charm][charm].
+
+[glow]: https://github.com/charmbracelet/glow
+[charm]: https://github.com/charmbracelet/charm
+
+
+## Spinner
+
+<img src="https://stuff.charm.sh/bubbles-examples/spinner.gif" width="400" alt="Spinner Example">
+
+A spinner, useful for indicating that some kind an operation is happening.
+There are a couple default ones, but you can also pass your own ”frames.”
+
+* [Example code](https://github.com/charmbracelet/tea/tree/master/examples/spinner/main.go)
+
+
+## Text Input
+
+<img src="https://stuff.charm.sh/bubbles-examples/textinput.gif" width="400" alt="Text Input Example">
+
+A text input field, akin to an `<input type="text">` in HTML. Supports unicode,
+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)
+
+
+## Paginator
+
+<img src="https://stuff.charm.sh/bubbles-examples/pagination.gif" width="200" alt="Paginator Example">
+
+A component for handling pagination logic and optionally drawing pagination UI.
+Supports "dot-style" pagination (similar to what you might see on iOS) and
+numeric page numbering, but you could also just use this component for the
+logic and visualize pagination however you like.
+
+This component is used in [Glow][glow] to browse documents and [Charm][charm] to
+browse SSH keys.
+
+
+## Viewport
+
+<img src="https://stuff.charm.sh/bubbles-examples/viewport.gif" width="600" alt="Viewport Example">
+
+A viewport for vertically scrolling content. Optionally includes standard
+pager keybindings and mouse wheel support. A high performance mode is available
+for applications which make use of the alterate screen buffer.
+
+* [Example code](https://github.com/charmbracelet/tea/tree/master/examples/pager/main.go)
+
+This compoent is well complimented with [Reflow][reflow] for ANSI-aware
+indenting and text wrapping.
+
+[reflow]: https://github.com/muesli/reflow
 
-⚠️  This project is a pre-release! Check back later.
 
 ## License
 
 [MIT](https://github.com/charmbracelet/teaparty/raw/master/LICENSE)
+
+
+***
+
+A [Charm](https://charm.sh) project.
+
+<img alt="the Charm logo" src="https://stuff.charm.sh/charm-badge.jpg" width="400">
+
+Charm热爱开源!

go.mod

@@ -3,10 +3,9 @@ module github.com/charmbracelet/bubbles
 go 1.13
 
 require (
-	github.com/charmbracelet/bubbletea v0.8.3-0.20200622174044-8bab4bce9a84
+	github.com/atotto/clipboard v0.1.2
+	github.com/charmbracelet/bubbletea v0.12.0
 	github.com/mattn/go-runewidth v0.0.9
-	github.com/muesli/termenv v0.5.3-0.20200617154346-da5de72b61c0
-	golang.org/x/crypto v0.0.0-20200604202706-70a84ac30bf9 // indirect
+	github.com/muesli/termenv v0.7.4
+	golang.org/x/sys v0.0.0-20201015000850-e3ed0017c211 // indirect
 )
-
-replace github.com/charmbracelet/bubbletea => ../bubbletea

go.sum

@@ -1,3 +1,9 @@
+github.com/atotto/clipboard v0.1.2 h1:YZCtFu5Ie8qX2VmVTBnrqLSiU9XOWwqNRmdT3gIQzbY=
+github.com/atotto/clipboard v0.1.2/go.mod h1:ZY9tmq7sm5xIbd9bOK4onWV4S6X0u6GY7Vn0Yu86PYI=
+github.com/charmbracelet/bubbletea v0.12.0 h1:/pUHp1GWRDyK1TJAWkXrnRH1u8Xc5076oH/J0NHxH+M=
+github.com/charmbracelet/bubbletea v0.12.0/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=
 github.com/google/goterm v0.0.0-20190703233501-fc88cf888a3f/go.mod h1:nOFQdrUlIlx6M6ODdSpBj1NVA+VgLC6kmw60mkw34H4=
 github.com/lucasb-eyer/go-colorful v1.0.3 h1:QIbQXiugsb+q10B+MI+7DI1oQLdmnep86tWFlaaUAac=
@@ -6,19 +12,22 @@ github.com/mattn/go-isatty v0.0.12 h1:wuysRhFDzyxgEmMf5xjvJ2M9dZoWAXNNr5LSBS7uHX
 github.com/mattn/go-isatty v0.0.12/go.mod h1:cbi8OIDigv2wuxKPP5vlRcQ1OAZbq2CE4Kysco4FUpU=
 github.com/mattn/go-runewidth v0.0.9 h1:Lm995f3rfxdpd6TSmuVCHVb/QhupuXlYr8sCI/QdE+0=
 github.com/mattn/go-runewidth v0.0.9/go.mod h1:H031xJmbD/WCDINGzjvQ9THkh0rPKHF+m2gUSrubnMI=
-github.com/muesli/termenv v0.5.3-0.20200617154346-da5de72b61c0 h1:IASsj5pQ478TEN9TLiuhP+ugUQEotZ1QdzQvcJUQ1dM=
-github.com/muesli/termenv v0.5.3-0.20200617154346-da5de72b61c0/go.mod h1:O1/I6sw+6KcrgAmcs6uiUVr7Lui+DNVbHTzt9Lm/PlI=
-github.com/pkg/term v0.0.0-20200520122047-c3ffed290a03 h1:pd4YKIqCB0U7O2I4gWHgEUA2mCEOENmco0l/bM957bU=
-github.com/pkg/term v0.0.0-20200520122047-c3ffed290a03/go.mod h1:Z9+Ul5bCbBKnbCvdOWbLqTHhJiYV414CURZJba6L8qA=
+github.com/muesli/termenv v0.7.2 h1:r1raklL3uKE7rOvWgSenmEm2px+dnc33OTisZ8YR1fw=
+github.com/muesli/termenv v0.7.2/go.mod h1:ct2L5N2lmix82RaY3bMWwVu/jUFc9Ule0KGDCiKYPh8=
+github.com/muesli/termenv v0.7.4 h1:/pBqvU5CpkY53tU0vVn+xgs2ZTX63aH5nY+SSps5Xa8=
+github.com/muesli/termenv v0.7.4/go.mod h1:pZ7qY9l3F7e5xsAOS0zCew2tME+p7bWeBkotCEcIIcc=
+github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/crypto v0.0.0-20200510223506-06a226fb4e37 h1:cg5LA/zNPRzIXIWSCxQW10Rvpy94aQh3LT/ShoCpkHw=
-golang.org/x/crypto v0.0.0-20200510223506-06a226fb4e37/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
-golang.org/x/crypto v0.0.0-20200604202706-70a84ac30bf9 h1:vEg9joUBmeBcK9iSJftGNf3coIG4HqZElCPehJsfAYM=
-golang.org/x/crypto v0.0.0-20200604202706-70a84ac30bf9/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
+golang.org/x/crypto v0.0.0-20201012173705-84dcc777aaee h1:4yd7jl+vXjalO5ztz6Vc1VADv+S/80LGJmyl1ROJ2AI=
+golang.org/x/crypto v0.0.0-20201012173705-84dcc777aaee/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200116001909-b77594299b42/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20200620081246-981b61492c35 h1:wb/9mP8eUAmHfkM8RmpeLq6nUA7c2i5+bQOtcDftjaE=
-golang.org/x/sys v0.0.0-20200620081246-981b61492c35/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200916030750-2334cc1a136f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20201009025420-dfb3f7c4e634 h1:bNEHhJCnrwMKNMmOx3yAynp5vs5/gRy+XWFtZFu7NBM=
+golang.org/x/sys v0.0.0-20201009025420-dfb3f7c4e634/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20201015000850-e3ed0017c211 h1:9UQO31fZ+0aKQOFldThf7BKPMJTiBfWycGh/u3UoO88=
+golang.org/x/sys v0.0.0-20201015000850-e3ed0017c211/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=

paginator/paginator.go

@@ -13,7 +13,7 @@ import (
 // Type specifies the way we render pagination.
 type Type int
 
-// Pagination rendering options
+// Pagination rendering options.
 const (
 	Arabic Type = iota
 	Dots
@@ -28,6 +28,7 @@ type Model struct {
 	ActiveDot         string
 	InactiveDot       string
 	ArabicFormat      string
+	UsePgUpPgDownKeys bool
 	UseLeftRightKeys  bool
 	UseUpDownKeys     bool
 	UseHLKeys         bool
@@ -105,6 +106,7 @@ func NewModel() Model {
 		ActiveDot:         "•",
 		InactiveDot:       "○",
 		ArabicFormat:      "%d/%d",
+		UsePgUpPgDownKeys: true,
 		UseLeftRightKeys:  true,
 		UseUpDownKeys:     false,
 		UseHLKeys:         true,
@@ -116,6 +118,14 @@ func NewModel() Model {
 func Update(msg tea.Msg, m Model) (Model, tea.Cmd) {
 	switch msg := msg.(type) {
 	case tea.KeyMsg:
+		if m.UsePgUpPgDownKeys {
+			switch msg.String() {
+			case "pgup":
+				m.PrevPage()
+			case "pgdown":
+				m.NextPage()
+			}
+		}
 		if m.UseLeftRightKeys {
 			switch msg.String() {
 			case "left":
@@ -154,11 +164,7 @@ func Update(msg tea.Msg, m Model) (Model, tea.Cmd) {
 }
 
 // View renders the pagination to a string.
-func View(model tea.Model) string {
-	m, ok := model.(Model)
-	if !ok {
-		return "could not perform assertion on model"
-	}
+func View(m Model) string {
 	switch m.Type {
 	case Dots:
 		return dotsView(m)

spinner/spinner.go

@@ -7,25 +7,17 @@ import (
 	"github.com/muesli/termenv"
 )
 
+const (
+	defaultFPS = time.Second / 10
+)
+
 // Spinner is a set of frames used in animating the spinner.
-type Spinner = int
-
-// Available types of spinners
-const (
-	Line Spinner = iota
-	Dot
-)
-
-const (
-	defaultFPS = 9
-)
+type Spinner = []string
 
 var (
-	// Spinner frames
-	spinners = map[Spinner][]string{
-		Line: {"|", "/", "-", "\\"},
-		Dot:  {"⣾ ", "⣽ ", "⣻ ", "⢿ ", "⡿ ", "⣟ ", "⣯ ", "⣷ "},
-	}
+	// Some spinners to choose from. You could also make your own.
+	Line = Spinner([]string{"|", "/", "-", "\\"})
+	Dot  = Spinner([]string{"⣾ ", "⣽ ", "⣻ ", "⢿ ", "⡿ ", "⣟ ", "⣯ ", "⣷ "})
 
 	color = termenv.ColorProfile().Color
 )
@@ -35,10 +27,10 @@ var (
 type Model struct {
 
 	// Type is the set of frames to use. See Spinner.
-	Type Spinner
+	Frames Spinner
 
-	// FPS is the speed at which the ticker should tick
-	FPS int
+	// FPS is the speed at which the ticker should tick.
+	FPS time.Duration
 
 	// ForegroundColor sets the background color of the spinner. It can be a
 	// hex code or one of the 256 ANSI colors. If the terminal emulator can't
@@ -52,67 +44,129 @@ type Model struct {
 	// (per github.com/muesli/termenv).
 	BackgroundColor string
 
-	// CustomMsgFunc can be used to a custom message on tick. This can be
-	// useful when you have spinners in different parts of your application and
-	// want to differentiate between the messages for clarity and simplicity.
-	// If nil, this setting is ignored.
-	CustomMsgFunc func() tea.Msg
+	// MinimumLifetime is the minimum amount of time the spinner can run. Any
+	// logic around this can be implemented in view that implements this
+	// spinner. If HideFor is set MinimumLifetime will be added on top of
+	// HideFor. In other words, if HideFor is 100ms and MinimumLifetime is
+	// 200ms then MinimumLifetime will expire after 300ms.
+	//
+	// MinimumLifetime is optional.
+	//
+	// This is considered experimental and may not appear in future versions of
+	// this library.
+	MinimumLifetime time.Duration
+
+	// HideFor can be used to wait to show the spinner until a certain amount
+	// of time has passed. This can be useful for preventing flicking when load
+	// times are very fast.
+	// Optional.
+	//
+	// This is considered experimental and may not appear in future versions of
+	// this library.
+	HideFor time.Duration
 
 	frame     int
+	startTime time.Time
+}
+
+// Start resets resets the spinner start time. For use with MinimumLifetime and
+// MinimumStartTime. Optional.
+//
+// This is considered experimental and may not appear in future versions of
+// this library.
+func (m *Model) Start() {
+	m.startTime = time.Now()
+}
+
+// hidden returns whether or not Model.HideFor is in effect.
+func (m Model) hidden() bool {
+	if m.startTime.IsZero() {
+		return false
+	}
+	if m.HideFor == 0 {
+		return false
+	}
+	return m.startTime.Add(m.HideFor).After(time.Now())
+}
+
+// finished returns whether Model.MinimumLifetimeReached has been met.
+func (m Model) finished() bool {
+	if m.startTime.IsZero() {
+		return true
+	}
+	if m.MinimumLifetime == 0 {
+		return true
+	}
+	return m.startTime.Add(m.HideFor).Add(m.MinimumLifetime).Before(time.Now())
+}
+
+// Visible returns whether or not the view should be rendered. Works in
+// conjunction with Model.HideFor and Model.MinimumLifetimeReached. You should
+// use this message directly to determine whether or not to render this view in
+// the parent view and whether to continue sending spin messaging in the
+// parent update function.
+//
+// Also note that using this function is optional and generally considered for
+// advanced use only. Most of the time your application logic will determine
+// whether or not this view should be used.
+//
+// This is considered experimental and may not appear in future versions of
+// this library.
+func (m Model) Visible() bool {
+	return !m.hidden() && !m.finished()
 }
 
 // NewModel returns a model with default values.
 func NewModel() Model {
 	return Model{
-		Type: Line,
+		Frames: Line,
 		FPS:    defaultFPS,
 	}
 }
 
 // TickMsg indicates that the timer has ticked and we should render a frame.
-type TickMsg struct{}
+type TickMsg struct {
+	Time time.Time
+}
 
 // Update is the Tea update function. This will advance the spinner one frame
 // every time it's called, regardless the message passed, so be sure the logic
 // is setup so as not to call this Update needlessly.
 func Update(msg tea.Msg, m Model) (Model, tea.Cmd) {
+	if _, ok := msg.(TickMsg); ok {
 		m.frame++
-	if m.frame >= len(spinners[m.Type]) {
+		if m.frame >= len(m.Frames) {
 			m.frame = 0
 		}
-	if m.CustomMsgFunc != nil {
 		return m, Tick(m)
 	}
-	return m, Tick(m)
+	return m, nil
 }
 
 // View renders the model's view.
 func View(model Model) string {
-	s := spinners[model.Type]
-	if model.frame >= len(s) {
-		return "[error]"
+	if model.frame >= len(model.Frames) {
+		return "error"
 	}
 
-	str := s[model.frame]
+	frame := model.Frames[model.frame]
 
 	if model.ForegroundColor != "" || model.BackgroundColor != "" {
 		return termenv.
-			String(str).
+			String(frame).
 			Foreground(color(model.ForegroundColor)).
 			Background(color(model.BackgroundColor)).
 			String()
 	}
 
-	return str
+	return frame
 }
 
 // Tick is the command used to advance the spinner one frame.
-func Tick(model Model) tea.Cmd {
-	return func() tea.Msg {
-		time.Sleep(time.Second / time.Duration(model.FPS))
-		if model.CustomMsgFunc != nil {
-			return model.CustomMsgFunc()
-		}
-		return TickMsg{}
+func Tick(m Model) tea.Cmd {
+	return tea.Tick(m.FPS, func(t time.Time) tea.Msg {
+		return TickMsg{
+			Time: t,
 		}
+	})
 }

textinput/textinput.go

@@ -5,6 +5,7 @@ import (
 	"time"
 	"unicode"
 
+	"github.com/atotto/clipboard"
 	tea "github.com/charmbracelet/bubbletea"
 	rw "github.com/mattn/go-runewidth"
 	"github.com/muesli/termenv"
@@ -15,15 +16,10 @@ const (
 )
 
 var (
-	// color is a helper for returning colors
+	// color is a helper for returning colors.
 	color func(s string) termenv.Color = termenv.ColorProfile().Color
 )
 
-// ErrMsg indicates there's been an error. We don't handle errors in the this
-// package; we're expecting errors to be handle in the program that implements
-// this text input.
-type ErrMsg error
-
 // Model is the Tea model for this text input element.
 type Model struct {
 	Err              error
@@ -126,6 +122,47 @@ func (m *Model) Reset() {
 	m.blink = false
 }
 
+// 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)
+
+	availSpace := m.CharLimit - len(m.value)
+
+	// If the char limit's been reached cancel
+	if m.CharLimit > 0 && availSpace <= 0 {
+		return
+	}
+
+	// If there's not enough space to paste the whole thing cut the pasted
+	// runes down so they'll fit
+	if availSpace < len(paste) {
+		paste = paste[:len(paste)-availSpace]
+	}
+
+	// Stuff before and after the cursor
+	head := m.value[:m.pos]
+	tailSrc := m.value[m.pos:]
+	tail := make([]rune, len(tailSrc))
+	copy(tail, tailSrc)
+
+	// Insert pasted runes
+	for _, r := range paste {
+		head = append(head, r)
+		availSpace--
+		m.pos++
+		if m.CharLimit > 0 && availSpace <= 0 {
+			break
+		}
+	}
+
+	// Put it all back together
+	m.value = append(head, tail...)
+}
+
 // If a max width is defined, perform some logic to treat the visible area
 // as a horizontally scrolling viewport.
 func (m *Model) handleOverflow() {
@@ -139,7 +176,6 @@ func (m *Model) handleOverflow() {
 	m.offsetRight = min(m.offsetRight, len(m.value))
 
 	if m.pos < m.offset {
-
 		m.offset = m.pos
 
 		w := 0
@@ -154,9 +190,7 @@ func (m *Model) handleOverflow() {
 		}
 
 		m.offsetRight = m.offset + i
-
 	} else if m.pos >= m.offsetRight {
-
 		m.offsetRight = m.pos
 
 		w := 0
@@ -171,7 +205,6 @@ func (m *Model) handleOverflow() {
 		}
 
 		m.offset = m.offsetRight - (len(runes) - 1 - i)
-
 	}
 }
 
@@ -229,7 +262,7 @@ func (m *Model) wordRight() {
 	i := m.pos
 
 	for i < len(m.value) {
-		if unicode.IsSpace(rune(m.value[i])) {
+		if unicode.IsSpace(m.value[i]) {
 			m.pos++
 			i++
 		} else {
@@ -238,7 +271,7 @@ func (m *Model) wordRight() {
 	}
 
 	for i < len(m.value) {
-		if !unicode.IsSpace(rune(m.value[i])) {
+		if !unicode.IsSpace(m.value[i]) {
 			m.pos++
 			i++
 		} else {
@@ -282,9 +315,11 @@ func Update(msg tea.Msg, m Model) (Model, tea.Cmd) {
 			fallthrough
 		case tea.KeyDelete:
 			if len(m.value) > 0 {
-				m.value = append(m.value[:m.pos-1], m.value[m.pos:]...)
+				m.value = append(m.value[:max(0, m.pos-1)], m.value[m.pos:]...)
+				if m.pos > 0 {
 					m.pos--
 				}
+			}
 		case tea.KeyLeft:
 			if msg.Alt { // alt+left arrow, back one word
 				m.wordLeft()
@@ -320,6 +355,8 @@ func Update(msg tea.Msg, m Model) (Model, tea.Cmd) {
 			m.value = m.value[m.pos:]
 			m.pos = 0
 			m.offset = 0
+		case tea.KeyCtrlV: // ^V paste
+			m.Paste()
 		case tea.KeyRune: // input a regular character
 
 			if msg.Alt {
@@ -340,9 +377,6 @@ func Update(msg tea.Msg, m Model) (Model, tea.Cmd) {
 			}
 		}
 
-	case ErrMsg:
-		m.Err = msg
-
 	case BlinkMsg:
 		m.blink = !m.blink
 		return m, Blink(m)
@@ -354,19 +388,14 @@ func Update(msg tea.Msg, m Model) (Model, tea.Cmd) {
 }
 
 // View renders the textinput in its current state.
-func View(model tea.Model) string {
-	m, ok := model.(Model)
-	if !ok {
-		return "could not perform assertion on model"
-	}
-
+func View(m Model) string {
 	// Placeholder text
-	if m.value == nil && m.Placeholder != "" {
+	if len(m.value) == 0 && m.Placeholder != "" {
 		return placeholderView(m)
 	}
 
 	value := m.value[m.offset:m.offsetRight]
-	pos := m.pos - m.offset
+	pos := max(0, m.pos-m.offset)
 
 	v := m.colorText(string(value[:pos]))
 
@@ -394,7 +423,7 @@ func View(model tea.Model) string {
 	return m.Prompt + v
 }
 
-// placeholderView
+// placeholderView.
 func placeholderView(m Model) string {
 	var (
 		v string
@@ -403,10 +432,7 @@ func placeholderView(m Model) string {
 
 	// Cursor
 	if m.blink && m.PlaceholderColor != "" {
-		v += cursorView(
-			m.colorPlaceholder(p[:1]),
-			m,
-		)
+		v += cursorView(m.colorPlaceholder(p[:1]), m)
 	} else {
 		v += cursorView(p[:1], m)
 	}

viewport/viewport.go

@@ -7,6 +7,10 @@ import (
 	tea "github.com/charmbracelet/bubbletea"
 )
 
+const (
+	spacebar = " "
+)
+
 // MODEL
 
 type Model struct {
@@ -33,29 +37,21 @@ type Model struct {
 	lines []string
 }
 
-// TODO: do we really need this?
-func NewModel(width, height int) Model {
-	return Model{
-		Width:  width,
-		Height: height,
-	}
-}
-
-// TODO: do we really need this?
-func (m Model) SetSize(yPos, width, height int) {
-	m.YPosition = yPos
-	m.Width = width
-	m.Height = height
-}
-
 // AtTop returns whether or not the viewport is in the very top position.
 func (m Model) AtTop() bool {
 	return m.YOffset <= 0
 }
 
-// AtBottom returns whether or not the viewport is at the very botom position.
+// AtBottom returns whether or not the viewport is at or past the very bottom
+// position.
 func (m Model) AtBottom() bool {
-	return m.YOffset >= len(m.lines)-m.Height-1
+	return m.YOffset >= len(m.lines)-1-m.Height
+}
+
+// PastBottom returns whether or not the viewport is scrolled beyond the last
+// line. This can happen when adjusting the viewport height.
+func (m Model) PastBottom() bool {
+	return m.YOffset > len(m.lines)-1-m.Height
 }
 
 // Scrollpercent returns the amount scrolled as a float between 0 and 1.
@@ -65,7 +61,7 @@ func (m Model) ScrollPercent() float64 {
 	}
 	y := float64(m.YOffset)
 	h := float64(m.Height)
-	t := float64(len(m.lines))
+	t := float64(len(m.lines) - 1)
 	v := y / (t - h)
 	return math.Max(0.0, math.Min(1.0, v))
 }
@@ -77,7 +73,7 @@ func (m *Model) SetContent(s string) {
 	m.lines = strings.Split(s, "\n")
 }
 
-// Return the lines that should currently be visible in the viewport
+// Return the lines that should currently be visible in the viewport.
 func (m Model) visibleLines() (lines []string) {
 	if len(m.lines) > 0 {
 		top := max(0, m.YOffset)
@@ -96,7 +92,7 @@ func (m *Model) ViewDown() []string {
 
 	m.YOffset = min(
 		m.YOffset+m.Height,      // target
-		len(m.lines)-m.Height, // fallback
+		len(m.lines)-1-m.Height, // fallback
 	)
 
 	return m.visibleLines()
@@ -124,7 +120,7 @@ func (m *Model) HalfViewDown() (lines []string) {
 
 	m.YOffset = min(
 		m.YOffset+m.Height/2,    // target
-		len(m.lines)-m.Height, // fallback
+		len(m.lines)-1-m.Height, // fallback
 	)
 
 	if len(m.lines) > 0 {
@@ -156,20 +152,26 @@ func (m *Model) HalfViewUp() (lines []string) {
 	return lines
 }
 
-// LineDown moves the view up by the given number of lines.
+// LineDown moves the view down by the given number of lines.
 func (m *Model) LineDown(n int) (lines []string) {
 	if m.AtBottom() || n == 0 {
 		return nil
 	}
 
+	// Make sure the number of lines by which we're going to scroll isn't
+	// greater than the number of lines we actually have left before we reach
+	// the bottom.
+	maxDelta := (len(m.lines) - 1) - (m.YOffset + m.Height) // number of lines - viewport bottom edge
+	n = min(n, maxDelta)
+
 	m.YOffset = min(
 		m.YOffset+n,             // target
-		len(m.lines)-m.Height, // fallback
+		len(m.lines)-1-m.Height, // fallback
 	)
 
 	if len(m.lines) > 0 {
-		top := max(0, m.YOffset+m.Height-n)
-		bottom := min(len(m.lines)-1, m.YOffset+m.Height)
+		top := max(m.YOffset+m.Height-n, 0)
+		bottom := min(m.YOffset+m.Height, len(m.lines)-1)
 		lines = m.lines[top:bottom]
 	}
 
@@ -183,11 +185,45 @@ func (m *Model) LineUp(n int) (lines []string) {
 		return nil
 	}
 
+	// Make sure the number of lines by which we're going to scroll isn't
+	// greater than the number of lines we are from the top.
+	n = min(n, m.YOffset)
+
 	m.YOffset = max(m.YOffset-n, 0)
 
 	if len(m.lines) > 0 {
 		top := max(0, m.YOffset)
-		bottom := min(len(m.lines)-1, m.YOffset+n)
+		bottom := min(m.YOffset+n, len(m.lines)-1)
+		lines = m.lines[top:bottom]
+	}
+
+	return lines
+}
+
+// GotoTop sets the viewport to the top position.
+func (m *Model) GotoTop() (lines []string) {
+	if m.AtTop() {
+		return nil
+	}
+
+	m.YOffset = 0
+
+	if len(m.lines) > 0 {
+		top := m.YOffset
+		bottom := min(m.YOffset+m.Height, len(m.lines)-1)
+		lines = m.lines[top:bottom]
+	}
+
+	return lines
+}
+
+// GotoTop sets the viewport to the bottom position.
+func (m *Model) GotoBottom() (lines []string) {
+	m.YOffset = max(len(m.lines)-1-m.Height, 0)
+
+	if len(m.lines) > 0 {
+		top := m.YOffset
+		bottom := max(len(m.lines)-1, 0)
 		lines = m.lines[top:bottom]
 	}
 
@@ -206,6 +242,8 @@ func Sync(m Model) tea.Cmd {
 		return nil
 	}
 
+	// 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)
 
@@ -216,9 +254,9 @@ func Sync(m Model) tea.Cmd {
 	)
 }
 
-// ViewDown is a high performance command that moves the viewport up by one
-// viewport height. Use Model.ViewDown to get the lines that should be
-// rendered. For example:
+// ViewDown is a high performance command that moves the viewport up by a given
+// numer of lines. Use Model.ViewDown to get the lines that should be rendered.
+// For example:
 //
 //     lines := model.ViewDown(1)
 //     cmd := ViewDown(m, lines)
@@ -230,8 +268,8 @@ func ViewDown(m Model, lines []string) tea.Cmd {
 	return tea.ScrollDown(lines, m.YPosition, m.YPosition+m.Height)
 }
 
-// ViewUp is a high performance command the moves the viewport down by one
-// viewport height. Use Model.ViewDown to get the lines that should be
+// ViewUp is a high performance command the moves the viewport down by a given
+// number of lines height. Use Model.ViewDown to get the lines that should be
 // rendered.
 func ViewUp(m Model, lines []string) tea.Cmd {
 	if len(lines) == 0 {
@@ -240,46 +278,6 @@ func ViewUp(m Model, lines []string) tea.Cmd {
 	return tea.ScrollUp(lines, m.YPosition, m.YPosition+m.Height)
 }
 
-// HalfViewDown is a high performance command the moves the viewport down by
-// half of the height of the viewport. Use Model.HalfViewDown to get the lines
-// that should be rendered.
-func HalfViewDown(m Model, lines []string) tea.Cmd {
-	if len(lines) == 0 {
-		return nil
-	}
-	return tea.ScrollDown(lines, m.YPosition, m.YPosition+m.Height)
-}
-
-// HalfViewUp is a high performance command the moves the viewport up by
-// half of the height of the viewport. Use Model.HalfViewUp to get the lines
-// that should be rendered.
-func HalfViewUp(m Model, lines []string) tea.Cmd {
-	if len(lines) == 0 {
-		return nil
-	}
-	return tea.ScrollUp(lines, m.YPosition, m.YPosition+m.Height)
-}
-
-// LineDown is a high performance command the moves the viewport down by
-// a given number of lines. Use Model.LineDown to get the lines that should be
-// rendered.
-func LineDown(m Model, lines []string) tea.Cmd {
-	if len(lines) == 0 {
-		return nil
-	}
-	return tea.ScrollDown(lines, m.YPosition, m.YPosition+m.Height)
-}
-
-// LineDown is a high performance command the moves the viewport up by a given
-// number of lines. Use Model.LineDown to get the lines that should be
-// rendered.
-func LineUp(m Model, lines []string) tea.Cmd {
-	if len(lines) == 0 {
-		return nil
-	}
-	return tea.ScrollUp(lines, m.YPosition, m.YPosition+m.Height)
-}
-
 // UPDATE
 
 // Update runs the update loop with default keybindings similar to popular
@@ -289,24 +287,17 @@ func Update(msg tea.Msg, m Model) (Model, tea.Cmd) {
 	var cmd tea.Cmd
 
 	switch msg := msg.(type) {
-
 	case tea.KeyMsg:
 		switch msg.String() {
 		// Down one page
-		case "pgdown":
-			fallthrough
-		case " ": // spacebar
-			fallthrough
-		case "f":
+		case "pgdown", spacebar, "f":
 			lines := m.ViewDown()
 			if m.HighPerformanceRendering {
 				cmd = ViewDown(m, lines)
 			}
 
 		// Up one page
-		case "pgup":
-			fallthrough
-		case "b":
+		case "pgup", "b":
 			lines := m.ViewUp()
 			if m.HighPerformanceRendering {
 				cmd = ViewUp(m, lines)
@@ -316,32 +307,43 @@ func Update(msg tea.Msg, m Model) (Model, tea.Cmd) {
 		case "d":
 			lines := m.HalfViewDown()
 			if m.HighPerformanceRendering {
-				cmd = HalfViewDown(m, lines)
+				cmd = ViewDown(m, lines)
 			}
 
 		// Up half page
 		case "u":
 			lines := m.HalfViewUp()
 			if m.HighPerformanceRendering {
-				cmd = HalfViewUp(m, lines)
+				cmd = ViewUp(m, lines)
 			}
 
 		// Down one line
-		case "down":
-			fallthrough
-		case "j":
+		case "down", "j":
 			lines := m.LineDown(1)
 			if m.HighPerformanceRendering {
-				cmd = LineDown(m, lines)
+				cmd = ViewDown(m, lines)
 			}
 
 		// Up one line
-		case "up":
-			fallthrough
-		case "k":
+		case "up", "k":
 			lines := m.LineUp(1)
 			if m.HighPerformanceRendering {
-				cmd = LineUp(m, lines)
+				cmd = ViewUp(m, lines)
+			}
+		}
+
+	case tea.MouseMsg:
+		switch msg.Type {
+		case tea.MouseWheelUp:
+			lines := m.LineUp(3)
+			if m.HighPerformanceRendering {
+				cmd = ViewUp(m, lines)
+			}
+
+		case tea.MouseWheelDown:
+			lines := m.LineDown(3)
+			if m.HighPerformanceRendering {
+				cmd = ViewDown(m, lines)
 			}
 		}
 	}
@@ -353,7 +355,6 @@ func Update(msg tea.Msg, m Model) (Model, tea.Cmd) {
 
 // View renders the viewport into a string.
 func View(m Model) string {
-
 	if m.HighPerformanceRendering {
 		// Just send newlines since we're doing to be rendering the actual
 		// content seprately. We still need send something that equals the
@@ -388,7 +389,3 @@ func max(a, b int) int {
 	}
 	return b
 }
-
-func clamp(val, low, high int) int {
-	return max(low, min(high, val))
-}