build method

@override Widget build(BuildContext context)

Build the Widget. Instead of overriding this function, override buildChild so that all gesture detectors can be set up automatically.

Implementation

@override
Widget build(BuildContext context) {
  ScrollbarControllerEncapsulation? scrollbarController =
      this.scrollbarController;
  scrollbarController?.updateScrollbarPainters();
  Widget child = buildChild(context);
  child = buildTransformAndScrollbars(context, child);

  if (scrollbarController != null) {
    child = RawGestureDetector(
      gestures: scrollbarController.getGesturesVertical(context),
      child: MouseRegion(
        onExit: (PointerExitEvent event) {
          switch (event.kind) {
            case PointerDeviceKind.mouse:
            case PointerDeviceKind.trackpad:
              if (scrollbarController.enableGestures) {
                scrollbarController.handleHoverExit(event);
              }
            case PointerDeviceKind.stylus:
            case PointerDeviceKind.invertedStylus:
            case PointerDeviceKind.unknown:
            case PointerDeviceKind.touch:
              break;
          }
        },
        onHover: (PointerHoverEvent event) {
          switch (event.kind) {
            case PointerDeviceKind.mouse:
            case PointerDeviceKind.trackpad:
              if (scrollbarController.enableGestures) {
                scrollbarController.handleHover(event);
              }
            case PointerDeviceKind.stylus:
            case PointerDeviceKind.invertedStylus:
            case PointerDeviceKind.unknown:
            case PointerDeviceKind.touch:
              break;
          }
        },
        child: child,
      ),
    );
    child = RawGestureDetector(
      gestures: scrollbarController.getGesturesHorizontal(context),
      child: child,
    );
  }

  if (!widget.noMouseDragScroll) {
    child = GestureDetector(
      behavior: HitTestBehavior.opaque,
      // Necessary when panning off screen.
      onScaleEnd: (onScaleEnd),
      onScaleStart: onScaleStart,
      onScaleUpdate: onScaleUpdate,
      onDoubleTapDown:
          widget.doubleTapToZoom ? ((d) => doubleTapDetails = d) : null,
      onDoubleTap: widget.doubleTapToZoom ? handleDoubleTap : null,
      child: child,
    );
  } else {
    child = GestureDetector(
      behavior: HitTestBehavior.opaque,
      supportedDevices: const {
        PointerDeviceKind.touch,
        PointerDeviceKind.trackpad,
        PointerDeviceKind.stylus,
        PointerDeviceKind.invertedStylus,
        PointerDeviceKind.unknown,
      },
      onScaleEnd: onScaleEnd,
      onScaleStart: onScaleStart,
      onScaleUpdate: onScaleUpdate,
      child: child,
    );
    child = GestureDetector(
      behavior: HitTestBehavior.opaque,
      onScaleEnd: (d) {
        onScaleEnd(d, outer: true);
      },
      onScaleStart: onScaleStart,
      onScaleUpdate: (d) {
        onScaleUpdate(d, inner: true);
      },
      onDoubleTapDown:
          widget.doubleTapToZoom ? ((d) => doubleTapDetails = d) : null,
      onDoubleTap: widget.doubleTapToZoom ? handleDoubleTap : null,
      child: child,
    );
  }

  return Listener(
    key: parentKey,
    onPointerSignal: receivedPointerSignal,
    child: child,
  );
}