ConnectBot Terminal

ConnectBot Terminal is a high-performance Jetpack Compose terminal emulator component for Android, providing accurate VT100/ANSI terminal emulation via libvterm.

Key Features

• Pure display component: Handles terminal emulation and rendering only; caller manages PTY, SSH/Telnet connections, I/O, etc.

• Jetpack Compose UI: Modern declarative UI with Canvas-based rendering

• Touch interactions: Pinch-to-zoom, scrollback, text selection with magnifying glass

• Thread-safe: Mutex-protected libvterm integration with safe callback handling

• Efficient rendering: Batched cell retrieval with format-aware run-length optimization

Core Components

• Terminal: JNI wrapper around libvterm providing input processing and keyboard event generation

• TerminalBuffer: Compose state management for terminal content and scrollback

• TermScreen: Main composable providing rendering and touch interaction

• SelectionManager: Text selection with character/word/line/block modes

• KeyboardHandler: Android KeyEvent to VTerm key mapping

Usage

In your Compose UI:

val emulator = TerminalEmulatorFactory.create(
    onKeyBoardInput = {
        // … send data to PTY/SSH/etc
    }
)

// Feed data from PTY/SSH
emulator.writeInput(data, offset, length)

// Render
Terminal(
    terminalEmulator = emulator
)

Keyboard visibility and temporary layouts

Set keyboardEnabled = true to accept input. With showSoftKeyboard = true (the default), entering the terminal and tapping its text area explicitly request the software keyboard, including when the editor already has focus. Android and the selected IME retain control over hardware-keyboard policy. Back dismissal is respected until the next explicit request; output and hardware keypresses do not reopen the keyboard. Setting showSoftKeyboard = false also disables tap-to-show. onImeVisibilityChanged reports observed window IME visibility, not request success.

Hosts such as ConnectBot's ConsoleScreen can pass resizeSuspended = true before opening a menu or temporarily moving interaction elsewhere. The terminal keeps its existing grid and pixel dimensions while still processing output. Intermediate container sizes are discarded. After suspension ends, only the latest size is applied, and an unchanged final size sends no resize callback.

Keep suspension active through popup dismissal and any keyboard restoration and layout animation, not just while the menu's expanded flag is true. The demo's settings menu illustrates retaining the pause until window focus returns and IME insets settle. Suspension does not hide the keyboard or change input eligibility. The option defaults to false, so existing hosts retain automatic resizing.

Architecture

PTY/SSH → TerminalEmulator.writeInput() → libvterm → Callbacks → TerminalEmulator → Terminal
Keyboard → TerminalEmulator.dispatchKey() → libvterm → onKeyboardInput() → PTY/SSH

Important: Callbacks must not call back into Terminal methods (causes deadlock). Defer work to avoid reentrancy.