layout method

@override PwBox layout(Context context, BoxConstraints incoming)

layout API.

Implementation

@override
PwBox layout(Context context, BoxConstraints incoming) {
  final EdgeInsets outer = (margin ?? EdgeInsets.zero).resolve(
    context.textDirection,
  );
  final EdgeInsets pad = (padding ?? EdgeInsets.zero).resolve(
    context.textDirection,
  );
  BoxConstraints inner = incoming.deflate(outer);
  final BoxConstraints? extra = constraints;
  if (extra != null) {
    inner = BoxConstraints(
      minWidth: extra.minWidth.clamp(inner.minWidth, inner.maxWidth),
      maxWidth: extra.maxWidth.clamp(inner.minWidth, inner.maxWidth),
      minHeight: extra.minHeight.clamp(inner.minHeight, inner.maxHeight),
      maxHeight: extra.maxHeight.clamp(inner.minHeight, inner.maxHeight),
    );
  }
  inner = inner.tighten(width: width, height: height);
  final BoxConstraints padded = inner.deflate(pad);
  final Widget? kid = child;
  PwBox? childBox;
  if (kid != null) {
    childBox = kid.layout(context, padded.loosen());
  }
  final PwSize childSize = childBox?.size ?? PwSize.zero;
  final double contentW = childSize.width + pad.horizontal;
  final double contentH = childSize.height + pad.vertical;
  final bool hasFill = color != null || decoration != null;
  // Match Flutter / package:pdf: alignment (or a painted fill) expands to the
  // parent's max width. Height expands only when the parent tightens it
  // (table cells) or sets a minHeight — never to an unbounded page leftover.
  final bool expandW =
      inner.hasBoundedWidth && (alignment != null || hasFill || kid == null);
  final bool heightTight =
      inner.hasBoundedHeight && (inner.maxHeight - inner.minHeight) < 1e-9;
  final bool expandH = heightTight || inner.minHeight > contentH;
  final double w = width ?? (expandW ? inner.maxWidth : contentW);
  final double h = height ??
      (expandH
          ? inner.constrainHeight(
              contentH < inner.minHeight ? inner.minHeight : contentH,
            )
          : contentH);
  final PwSize boxSize = inner.constrain(PwSize(w, h));
  final PwOffset childOff;
  if (childBox != null) {
    final PwSize padBox = PwSize(
      (boxSize.width - pad.horizontal).clamp(0, boxSize.width),
      (boxSize.height - pad.vertical).clamp(0, boxSize.height),
    );
    final Alignment resolved =
        alignment?.resolve(context.textDirection) ?? _startTop(context);
    final PwOffset aligned = resolved.alongOffset(
      padBox,
      childSize,
    );
    childOff = PwOffset(pad.left + aligned.dx, pad.top + aligned.dy);
  } else {
    childOff = PwOffset(pad.left, pad.top);
  }
  return ProxyBox(
    PwSize(
      incoming.constrainWidth(boxSize.width + outer.horizontal),
      incoming.constrainHeight(boxSize.height + outer.vertical),
    ),
    child: childBox,
    childOffset: PwOffset(outer.left + childOff.dx, outer.top + childOff.dy),
    decoration: decoration ?? (color == null ? null : BoxDecoration(color: color)),
  );
}