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Documentation Index

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Overview

The terminal package provides a shared terminal session using PTY (pseudo-terminal) with VT10x emulation. Multiple clients can connect to the same terminal and see synchronized output.

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Type

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Terminal

Wraps a PTY with VT10x terminal emulation and subscriber management. 
type Terminal struct {
    vt   vt10x.Terminal
    ptmx *os.File
    cmd  *exec.Cmd
    mu   sync.Mutex
    
    width   int
    height  int
    workDir string
    
    subscribers map[chan struct{}]struct{}
    subMu       sync.RWMutex
    closed      bool
    
    lastRender string
    dirty      bool
}

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Functions

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New

Creates a new terminal instance. 
func New(width, height int, workDir string) *Terminal
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width
int
required
Terminal width in columns (defaults to 80 if < 1)
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height
int
required
Terminal height in rows (defaults to 24 if < 1)
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workDir
string
required
Working directory for shell (defaults to “/app” if empty)
Example: 
term := terminal.New(120, 30, "/app/workspaces/my-project")

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Start

Starts the shell process and begins reading output. 
func (t *Terminal) Start() error
Returns: Error if PTY creation or shell start fails Behavior:
  • Creates VT10x terminal emulator
  • Spawns shell process (respects $SHELL env var, defaults to /bin/sh)
  • Sets environment: TERM=xterm-256color
  • Starts background read loop
Example: 
term := terminal.New(80, 24, "/app")
if err := term.Start(); err != nil {
    log.Fatal(err)
}

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Write

Sends input to the terminal (keyboard input, etc.). 
func (t *Terminal) Write(data []byte) (int, error)
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data
[]byte
required
Raw input data to send to PTY
Returns: Bytes written and error Example: 
// Send "ls" command
term.Write([]byte("ls\r"))

// Send Ctrl+C
term.Write([]byte{0x03})

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Render

Renders the current terminal state to a string with ANSI codes. 
func (t *Terminal) Render() string
Returns: Rendered terminal output with colors and formatting Features:
  • Caching: Returns cached render if terminal hasn’t changed
  • Colors: Full 256-color ANSI support
  • Cursor: Visual cursor using reverse video effect
  • Optimization: Run-length encoding for color sequences
Example: 
output := term.Render()
fmt.Print(output)

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Resize

Resizes the terminal dimensions. 
func (t *Terminal) Resize(width, height int)
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width
int
required
New width in columns
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height
int
required
New height in rows
Behavior:
  • Updates VT10x emulator size
  • Sends SIGWINCH via pty.Setsize()
  • Invalidates render cache

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Close

Closes the terminal and cleans up resources. 
func (t *Terminal) Close() error
Cleanup:
  • Closes all subscriber channels
  • Closes PTY file descriptor
  • Kills shell process

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Size

Returns current terminal dimensions. 
func (t *Terminal) Size() (width, height int)

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Subscription Pattern

The terminal supports multi-client subscriptions for real-time updates.

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Subscribe

Creates a channel for receiving update notifications. 
func (t *Terminal) Subscribe() chan struct{}
Returns: Channel that receives a signal on each terminal update Example: 
updates := term.Subscribe()
defer term.Unsubscribe(updates)

for range updates {
    output := term.Render()
    updateUI(output)
}

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Unsubscribe

Removes a subscription channel. 
func (t *Terminal) Unsubscribe(ch chan struct{})
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ch
chan struct{}
required
Channel returned by Subscribe()

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Implementation Details

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Read Loop

The background readLoop() goroutine:
  1. Reads from PTY (4KB buffer)
  2. Writes to VT10x emulator
  3. Marks terminal as dirty
  4. Broadcasts to all subscribers
  5. Exits when shell process terminates

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Render Optimization

// Return cached render if not dirty
if !t.dirty && t.lastRender != "" {
    return t.lastRender
}
The terminal caches renders and only re-renders when content changes, reducing CPU usage for idle terminals.

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Color Mapping

func fgColor(c vt10x.Color) string
func bgColor(c vt10x.Color) string
Maps VT10x colors to ANSI escape codes:
  • Colors 0-7: Standard ANSI (30-37, 40-47)
  • Colors 8-15: Bright ANSI (90-97, 100-107)
  • Colors 16-255: Extended palette (38;5;n, 48;5;n)

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Thread Safety

All public methods are thread-safe:
  • mu sync.Mutex protects terminal state
  • subMu sync.RWMutex protects subscriber map

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