show method

Implementation

void show() {
  // Build the overlay canvas + context first so we can measure text.
  _canvas = web.HTMLCanvasElement();
  final ctx = _canvas.getContext('2d');
  if (ctx == null) return;
  _surface = WebCanvasSurface(ctx as web.CanvasRenderingContext2D);

  // Lay out rows + compute size.
  _rows = [];
  var y = _padY;
  var maxTextW = 0.0;
  _surface.setFont(size: 12);
  for (final mi in _item.menuItems) {
    if (mi.isSeparator) {
      _rows.add(_MenuRow.separator(y));
      y += _sepH;
    } else {
      final w = _surface.measureTextWidth(mi.caption);
      if (w > maxTextW) maxTextW = w;
      _rows.add(_MenuRow.item(mi, y, _rowH));
      y += _rowH;
    }
  }
  _menuW = (maxTextW + _padX * 2).clamp(_minW, _maxW);
  _menuH = y + _padY;

  // Position in the viewport, anchored to the button's bottom-left.
  final a = _anchor.getBoundingClientRect();
  final dpr = web.window.devicePixelRatio.clamp(1.0, 3.0);
  var left = a.left + _anchorRect.x;
  var top = a.top + _anchorRect.bottom + 2;
  // Flip above if it would overflow the bottom.
  if (top + _menuH > web.window.innerHeight) {
    final above = a.top + _anchorRect.y - _menuH - 2;
    if (above > 4) top = above;
  }
  // Clamp into the viewport horizontally.
  left = (left).clamp(4.0, math.max(4.0, web.window.innerWidth - _menuW - 4));

  // Size the backing store for HiDPI and place the element.
  _canvas.width = (_menuW * dpr).round();
  _canvas.height = (_menuH * dpr).round();
  _canvas.style
    ..position = 'fixed'
    ..left = '${left}px'
    ..top = '${top}px'
    ..width = '${_menuW}px'
    ..height = '${_menuH}px'
    ..zIndex = '99999'
    ..borderRadius = '6px'
    ..boxShadow = '0 6px 18px rgba(0,0,0,0.18)';
  _surface.ctx.scale(dpr, dpr);

  // Fullscreen transparent backdrop to catch outside clicks.
  _backdrop = web.HTMLDivElement();
  _backdrop.style
    ..position = 'fixed'
    ..left = '0'
    ..top = '0'
    ..width = '100%'
    ..height = '100%'
    ..zIndex = '99998';
  _backdrop.onClick.listen((_) => dismiss());

  _subs.add(_canvas.onMouseMove.listen(_onMove));
  _subs.add(
    _canvas.onMouseLeave.listen((_) {
      _hover = -1;
      _paint();
    }),
  );
  _subs.add(_canvas.onMouseDown.listen(_onDown));

  _paint();
  web.document.body!.append(_backdrop);
  web.document.body!.append(_canvas);
}