Class SelectionManager

lib/selection-manager.ts:35–904

// ============================================================================

export class SelectionManager {
  private terminal: Terminal;
  private renderer: CanvasRenderer;
  private wasmTerm: GhosttyTerminal;
  private textarea: HTMLTextAreaElement;

  // Selection state - coordinates are in ABSOLUTE buffer space (viewportY + viewportRow)
  // This ensures selection persists correctly when scrolling
  private selectionStart: { col: number; absoluteRow: number } | null = null;
  private selectionEnd: { col: number; absoluteRow: number } | null = null;
  private isSelecting: boolean = false;
  private mouseDownTarget: EventTarget | null = null; // Track where mousedown occurred

  // Track rows that need redraw for clearing old selection
  // Using a Set prevents the overwrite bug where mousemove would clobber
  // the rows marked by clearSelection()
  private dirtySelectionRows: Set<number> = new Set();

  // Event emitter
  private selectionChangedEmitter = new EventEmitter<void>();

  // Store bound event handlers for cleanup
  private boundMouseUpHandler: ((e: MouseEvent) => void) | null = null;
  private boundContextMenuHandler: ((e: MouseEvent) => void) | null = null;
  private boundClickHandler: ((e: MouseEvent) => void) | null = null;
  private boundDocumentMouseMoveHandler: ((e: MouseEvent) => void) | null = null;

  // Auto-scroll state for drag selection
  private autoScrollInterval: ReturnType<typeof setInterval> | null = null;
  private autoScrollDirection: number = 0; // -1 = up, 0 = none, 1 = down
  private static readonly AUTO_SCROLL_EDGE_SIZE = 30; // pixels from edge to trigger scroll

  /**
   * Get current viewport Y position (how many lines scrolled into history)
   */
  private getViewportY(): number {
    const rawViewportY =
      typeof (this.terminal as any).getViewportY === 'function'
        ? (this.terminal as any).getViewportY()
        : (this.terminal as any).viewportY || 0;
    return Math.max(0, Math.floor(rawViewportY));
  }

  /**
   * Convert viewport row to absolute buffer row
   * Absolute row is an index into combined buffer: scrollback (0 to len-1) + screen (len to len+rows-1)
   */
  private viewportRowToAbsolute(viewportRow: number): number {
    const scrollbackLength = this.wasmTerm.getScrollbackLength();
    const viewportY = this.getViewportY();
    return scrollbackLength + viewportRow - viewportY;
  }

  /**
   * Convert absolute buffer row to viewport row (may be outside visible range)
   */
  private absoluteRowToViewport(absoluteRow: number): number {
    const scrollbackLength = this.wasmTerm.getScrollbackLength();