Add ProgramOptions for entering the altscreen and enabling the mouse

Because they run ansyncronously, the analogous commands, when run in
a Model's Init() function, could fire after the renderer has starting
writing to output, rendering artifacts to the commandline.

examples/fullscreen/main.go

@@ -16,7 +16,8 @@ type model int
 type tickMsg time.Time
 
 func main() {
-	if err := tea.NewProgram(model(5)).Start(); err != nil {
+	p := tea.NewProgram(model(5), tea.WithAltScreen())
+	if err := p.Start(); err != nil {
 		log.Fatal(err)
 	}
 }

examples/mouse/main.go

@@ -11,7 +11,8 @@ import (
 )
 
 func main() {
-	if err := tea.NewProgram(model{}).Start(); err != nil {
+	p := tea.NewProgram(model{}, tea.WithAltScreen(), tea.WithMouseAllMotion())
+	if err := p.Start(); err != nil {
 		log.Fatal(err)
 	}
 }
@@ -22,7 +23,7 @@ type model struct {
 }
 
 func (m model) Init() tea.Cmd {
-	return tea.Batch(tea.EnterAltScreen, tea.EnableMouseAllMotion)
+	return nil
 }
 
 func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {

examples/pager/main.go

@@ -53,15 +53,15 @@ func main() {
 		defer f.Close()
 	}
 
-	p := tea.NewProgram(model{content: string(content)})
+	p := tea.NewProgram(
+		model{content: string(content)},
 
-	// Use the full size of the terminal in its "alternate screen buffer"
-	p.EnterAltScreen()
-	defer p.ExitAltScreen()
+		// Use the full size of the terminal in its "alternate screen buffer"
+		tea.WithAltScreen(),
 
-	// We also turn on mouse support so we can track the mouse wheel
-	p.EnableMouseCellMotion()
-	defer p.DisableMouseCellMotion()
+		// Also turn on mouse support so we can track the mouse wheel
+		tea.WithMouseCellMotion(),
+	)
 
 	if err := p.Start(); err != nil {
 		fmt.Println("could not run program:", err)

tea.go

@@ -25,7 +25,7 @@ import (
 	"golang.org/x/term"
 )
 
-// Msg represents an action and is usually the result of an IO operation. It's
+// Msg represents an action and is usually the result of an IO operation. It
 // triggers the Update function, and henceforth, the UI.
 type Msg interface{}
 
@@ -52,23 +52,13 @@ type Model interface {
 // function.
 type Cmd func() Msg
 
-// Batch performs a bunch of commands concurrently with no ordering guarantees
-// about the results.
-func Batch(cmds ...Cmd) Cmd {
-	if len(cmds) == 0 {
-		return nil
-	}
-	return func() Msg {
-		return batchMsg(cmds)
-	}
-}
-
 // ProgramOption is used to set options when initializing a Program. Program can
 // accept a variable number of options.
 //
 // Example usage:
 //
 //     p := NewProgram(model, WithInput(someInput), WithOutput(someOutput))
+//
 type ProgramOption func(*Program)
 
 // WithOutput sets the output which, by default, is stdout. In most cases you
@@ -98,6 +88,67 @@ func WithoutCatchPanics() ProgramOption {
 	}
 }
 
+// WithAltScreen starts the program with the alternate screen buffer enabled
+// (i.e. the program starts in full window mode). Note that the altscreen will
+// be automatically exited when the program quits.
+//
+// Example:
+//
+//     p := tea.NewProgram(Model{}, tea.WithAltScreen())
+//     if err := p.Start(); err != nil {
+//         fmt.Println("Error running program:", err)
+//         os.Exit(1)
+//     }
+//
+// To enter the altscreen once the program has already started running use the
+// EnterAltScreen command.
+func WithAltScreen() ProgramOption {
+	return func(p *Program) {
+		p.startupOptions |= withAltScreen
+	}
+}
+
+// WithMouseCellMotion starts the program with the mouse enabled in "cell
+// motion" mode.
+//
+// Cell motion mode enables mouse click, release, and wheel events. Mouse
+// movement events are also captured if a mouse button is pressed (i.e., drag
+// events). Cell motion mode is better supported than all motion mode.
+//
+// To enable mouse cell motion once the program has already started running use
+// the EnableMouseCellMotion command. To disable the mouse when the program is
+// running use the DisableMouse command.
+//
+// The mouse will be automatically disabled when the program exits.
+func WithMouseCellMotion() ProgramOption {
+	return func(p *Program) {
+		p.startupOptions |= withMouseCellMotion // set
+		p.startupOptions &^= withMouseAllMotion // clear
+	}
+}
+
+// WithMouseAllMotion starts the program with the mouse enabled in "all motion"
+// mode.
+//
+// EnableMouseAllMotion is a special command that enables mouse click, release,
+// wheel, and motion events, which are delivered regardless of whether a mouse
+// button is pressed, effectively enabling support for hover interactions.
+//
+// Many modern terminals support this, but not all. If in doubt, use
+// EnableMouseCellMotion instead.
+//
+// To enable the mouse once the program has already started running use the
+// EnableMouseAllMotion command. To disable the mouse when the program is
+// running use the DisableMouse command.
+//
+// The mouse will be automatically disabled when the program exits.
+func WithMouseAllMotion() ProgramOption {
+	return func(p *Program) {
+		p.startupOptions |= withMouseAllMotion   // set
+		p.startupOptions &^= withMouseCellMotion // clear
+	}
+}
+
 // WithoutRenderer disables the renderer. When this is set output and log
 // statements will be plainly sent to stdout (or another output if one is set)
 // without any rendering and redrawing logic. In other words, printing and
@@ -112,6 +163,19 @@ func WithoutRenderer() ProgramOption {
 	}
 }
 
+// startupOptions contains configuration options to be run while the program
+// is initializing.
+//
+// The options here are treated as bits.
+type startupOptions byte
+
+// Available startup options.
+const (
+	withAltScreen startupOptions = 1 << iota
+	withMouseCellMotion
+	withMouseAllMotion
+)
+
 // inputStatus indicates the current state of the input. By default, input is
 // stdin, however we'll change this if input's not a TTY. The user can also set
 // the input.
@@ -144,6 +208,10 @@ func (i inputStatus) String() string {
 type Program struct {
 	initialModel Model
 
+	// Configuration options that will set as the program is initializing,
+	// treated as bits.  These options can be set via various ProgramOptions.
+	startupOptions startupOptions
+
 	mtx *sync.Mutex
 
 	output          io.Writer // where to send output. this will usually be os.Stdout.
@@ -172,6 +240,28 @@ type Program struct {
 	windowsStdin *os.File //nolint:golint,structcheck,unused
 }
 
+// Batch performs a bunch of commands concurrently with no ordering guarantees
+// about the results. Use a Batch to return several commands.
+//
+// Example:
+//
+//     func (m model) Init() Cmd {
+//	       return tea.Batch(someCommand, someOtherCommand)
+//     }
+//
+func Batch(cmds ...Cmd) Cmd {
+	if len(cmds) == 0 {
+		return nil
+	}
+	return func() Msg {
+		return batchMsg(cmds)
+	}
+}
+
+// batchMsg is the internal message used to perform a bunch of commands. You
+// can send a batchMsg with Batch.
+type batchMsg []Cmd
+
 // Quit is a special command that tells the Bubble Tea program to exit.
 func Quit() Msg {
 	return quitMsg{}
@@ -183,6 +273,10 @@ type quitMsg struct{}
 
 // EnterAltScreen is a special command that tells the Bubble Tea program to
 // enter alternate screen buffer.
+//
+// Because commands run asynchronously, this command should not be used in your
+// model's Init function. To initialize your program with the altscreen enabled
+// use the WithAltScreen ProgramOption instead.
 func EnterAltScreen() Msg {
 	return enterAltScreenMsg{}
 }
@@ -193,21 +287,45 @@ func EnterAltScreen() Msg {
 type enterAltScreenMsg struct{}
 
 // ExitAltScreen is a special command that tells the Bubble Tea program to exit
-// alternate screen buffer.
+// the alternate screen buffer. This command should be used to exit the
+// alternate screen buffer while the program is running.
+//
+// Note that the alternate screen buffer will be automatically exited when the
+// program quits.
 func ExitAltScreen() Msg {
 	return exitAltScreenMsg{}
 }
 
+// exitAltScreenMsg in an internal message signals that the program should exit
+// alternate screen buffer. You can send a exitAltScreenMsg with ExitAltScreen.
+type exitAltScreenMsg struct{}
+
+// EnableMouseCellMotion is a special command that enables mouse click,
+// release, and wheel events. Mouse movement events are also captured if
+// a mouse button is pressed (i.e., drag events).
+//
+// Because commands run asynchronously, this command should not be used in your
+// model's Init function. Use the WithMouseCellMotion ProgramOption instead.
+func EnableMouseCellMotion() Msg {
+	return enableMouseCellMotionMsg{}
+}
+
 // enableMouseCellMotionMsg is a special command that signals to start
 // listening for "cell motion" type mouse events (ESC[?1002l). To send an
 // enableMouseCellMotionMsg, use the EnableMouseCellMotion command.
 type enableMouseCellMotionMsg struct{}
 
-// EnableMouseCellMotion is a special command that enables mouse click,
-// release, wheel, events. Mouse movement events are also captured if a mouse
-// button is pressed (i.e., drag events).
-func EnableMouseCellMotion() Msg {
-	return enableMouseCellMotionMsg{}
+// EnableMouseAllMotion is a special command that enables mouse click, release,
+// wheel, and motion events, which are delivered regardless of whether a mouse
+// button is pressed, effectively enabling support for hover interactions.
+//
+// Many modern terminals support this, but not all. If in doubt, use
+// EnableMouseCellMotion instead.
+//
+// Because commands run asynchronously, this command should not be used in your
+// model's Init function. Use the WithMouseAllMotion ProgramOption instead.
+func EnableMouseAllMotion() Msg {
+	return enableMouseAllMotionMsg{}
 }
 
 // enableMouseAllMotionMsg is a special command that signals to start listening
@@ -215,33 +333,19 @@ func EnableMouseCellMotion() Msg {
 // enableMouseAllMotionMsg, use the EnableMouseAllMotion command.
 type enableMouseAllMotionMsg struct{}
 
-// EnableMouseAllMotion is a special command that enables mouse click, release,
-// and wheel events. Mouse movement events are delivered regardless of whether
-// a button is pressed. Many modern terminals support this, but not all. If in
-// doubt, use EnableMouseCellMotion instead.
-func EnableMouseAllMotion() Msg {
-	return enableMouseAllMotionMsg{}
+// DisableMouse is a special command that stops listening for mouse events.
+func DisableMouse() Msg {
+	return disableMouseMsg{}
 }
 
 // disableMouseMsg is an internal message that that signals to stop listening
 // for mouse events. To send a disableMouseMsg, use the DisableMouse command.
 type disableMouseMsg struct{}
 
-// DisableMouse is a special command that stops listening for mouse events.
-func DisableMouse() Msg {
-	return disableMouseMsg{}
-}
-
-// exitAltScreenMsg in an internal message signals that the program should exit
-// alternate screen buffer. You can send a exitAltScreenMsg with ExitAltScreen.
-type exitAltScreenMsg struct{}
-
-// batchMsg is the internal message used to perform a bunch of commands. You
-// can send a batchMsg with Batch.
-type batchMsg []Cmd
-
-// WindowSizeMsg is used to report on the terminal size. It's sent to Update
-// once initially and then on every terminal resize.
+// WindowSizeMsg is used to report the terminal size. It's sent to Update once
+// initially and then on every terminal resize. Note that Windows does not
+// have support for reporting when resizes occur as it does not support the
+// SIGWINCH signal.
 type WindowSizeMsg struct {
 	Width  int
 	Height int
@@ -347,11 +451,6 @@ func (p *Program) Start() error {
 		}()
 	}
 
-	// If no renderer is set use the standard one.
-	if p.renderer == nil {
-		p.renderer = newRenderer(p.output, p.mtx)
-	}
-
 	// Check if output is a TTY before entering raw mode, hiding the cursor and
 	// so on.
 	{
@@ -364,6 +463,21 @@ func (p *Program) Start() error {
 		}()
 	}
 
+	// If no renderer is set use the standard one.
+	if p.renderer == nil {
+		p.renderer = newRenderer(p.output, p.mtx)
+	}
+
+	// Honor program startup options.
+	if p.startupOptions&withAltScreen != 0 {
+		p.EnterAltScreen()
+	}
+	if p.startupOptions&withMouseCellMotion != 0 {
+		p.EnableMouseCellMotion()
+	} else if p.startupOptions&withMouseAllMotion != 0 {
+		p.EnableMouseAllMotion()
+	}
+
 	// Initialize program
 	model := p.initialModel
 	initCmd := model.Init()
@@ -490,7 +604,7 @@ func (p *Program) Start() error {
 // EnterAltScreen enters the alternate screen buffer, which consumes the entire
 // terminal window. ExitAltScreen will return the terminal to its former state.
 //
-// Deprecated. Use the EnterAltScreen() command instead.
+// Deprecated. Use the WithAltScreen ProgramOption instead.
 func (p *Program) EnterAltScreen() {
 	p.mtx.Lock()
 	defer p.mtx.Unlock()
@@ -510,7 +624,7 @@ func (p *Program) EnterAltScreen() {
 
 // ExitAltScreen exits the alternate screen buffer.
 //
-// Deprecated. Use the ExitAltScreen() command instead.
+// Deprecated. The altscreen will exited automatically when the program exits.
 func (p *Program) ExitAltScreen() {
 	p.mtx.Lock()
 	defer p.mtx.Unlock()
@@ -530,7 +644,7 @@ func (p *Program) ExitAltScreen() {
 // EnableMouseCellMotion enables mouse click, release, wheel and motion events
 // if a mouse button is pressed (i.e., drag events).
 //
-// Deprecated. Use the EnableMouseCellMotion() command instead.
+// Deprecated. Use the WithMouseCellMotion ProgramOption instead.
 func (p *Program) EnableMouseCellMotion() {
 	p.mtx.Lock()
 	defer p.mtx.Unlock()
@@ -540,7 +654,7 @@ func (p *Program) EnableMouseCellMotion() {
 // DisableMouseCellMotion disables Mouse Cell Motion tracking. This will be
 // called automatically when exiting a Bubble Tea program.
 //
-// Deprecated. Use the DisableMouse() command instead.
+// Deprecated. The mouse will automatically be disabled when the program exits.
 func (p *Program) DisableMouseCellMotion() {
 	p.mtx.Lock()
 	defer p.mtx.Unlock()
@@ -551,7 +665,7 @@ func (p *Program) DisableMouseCellMotion() {
 // regardless of whether a mouse button is pressed. Many modern terminals
 // support this, but not all.
 //
-// Deprecated. Use the EnableMouseAllMotion() command instead.
+// Deprecated. Use the WithMouseAllMotion ProgramOption instead.
 func (p *Program) EnableMouseAllMotion() {
 	p.mtx.Lock()
 	defer p.mtx.Unlock()
@@ -561,7 +675,7 @@ func (p *Program) EnableMouseAllMotion() {
 // DisableMouseAllMotion disables All Motion mouse tracking. This will be
 // called automatically when exiting a Bubble Tea program.
 //
-// Deprecated. Use the DisableMouse() command instead.
+// Deprecated. The mouse will automatically be disabled when the program exits.
 func (p *Program) DisableMouseAllMotion() {
 	p.mtx.Lock()
 	defer p.mtx.Unlock()