showOnScreen method

@override void showOnScreen({ RenderObject? descendant, Rect? rect, Duration duration = Duration.zero, Curve curve = Curves.ease, })

Attempt to make (a portion of) this or a descendant RenderObject visible on screen.

If descendant is provided, that RenderObject is made visible. If descendant is omitted, this RenderObject is made visible.

The optional rect parameter describes which area of that RenderObject should be shown on screen. If rect is null, the entire RenderObject (as defined by its paintBounds) will be revealed. The rect parameter is interpreted relative to the coordinate system of descendant if that argument is provided and relative to this RenderObject otherwise.

The duration parameter can be set to a non-zero value to bring the target object on screen in an animation defined by curve.

See also:

• RenderViewportBase.showInViewport, which RenderViewportBase and SingleChildScrollView delegate this method to.

Implementation

@override
void showOnScreen({
  RenderObject? descendant,
  Rect? rect,
  Duration duration = Duration.zero,
  Curve curve = Curves.ease,
}) {
  if (descendant != null) {
    // Shows the descendant in the selected/center position.
    final RevealedOffset revealedOffset =
        getOffsetToReveal(descendant, 0.5, rect: rect);
    if (duration == Duration.zero) {
      offset.jumpTo(revealedOffset.offset);
    } else {
      offset.animateTo(revealedOffset.offset,
          duration: duration, curve: curve);
    }
    rect = revealedOffset.rect;
  }

  super.showOnScreen(
    rect: rect,
    duration: duration,
    curve: curve,
  );
}