performLayout method

@override dynamic performLayout(PrinterConstraints constraints, PrinterCanvas canvas)

布局

Implementation

@override
performLayout(PrinterConstraints constraints, PrinterCanvas canvas) {
  PrinterConstraints childConstraints;
  actualSize = null;
  actualOffset = offset;
  if (size != null) {
    childConstraints = PrinterConstraints.constraints(constraints, size!);
  } else {
    childConstraints = constraints;
  }
  double maxWidth = 0;
  double width = 0;
  double height = 0; // 当前行高
  double top = 0;
  List<ControlBase> currentRow = [];
  List<List<ControlBase>> rows = [currentRow];
  for (var child in children) { // 计算大小并且设置Top偏移
    if (child.isRender) {
      if (this.wordWrap) {
        child.performLayout(PrinterConstraints(maxHeight: childConstraints.maxHeight, maxWidth: childConstraints.maxWidth), canvas);
        width += child.actualOffset!.x! + child.actualSize!.width!; // 计算当前行宽
        if (childConstraints.maxWidth < width) { // 超出换行
          top += height;
          height = child.actualSize!.height! + child.actualOffset!.y!;
          width = child.actualOffset!.x! + child.actualSize!.width!;
          currentRow = [];
          rows.add(currentRow);
        } else {
          height = Math.max(child.actualSize!.height! + child.actualOffset!.y!, height); // 计算当前行最高
        }
        currentRow.add(child);
        child.actualOffset = child.actualOffset!.translate(0, top); // 设置偏移
        maxWidth = Math.max(maxWidth, width); // 计算总高度
      } else {
        child.performLayout(PrinterConstraints(maxHeight: childConstraints.maxHeight, maxWidth: childConstraints.maxWidth - maxWidth), canvas);
        maxWidth += child.actualOffset!.x! + child.actualSize!.width!;
        height = Math.max(child.actualSize!.height! + child.actualOffset!.y!, height);
        currentRow.add(child);
      }
    }
  }


  if (this.align != AlignEnum.start) {
    maxWidth = childConstraints.maxWidth;
  }

  maxWidth = Math.max(maxWidth, minWidth);

  for (var row in rows) {
    _calcRowOffset(row, maxWidth);
  }

  if (size?.width != null && size!.width!.isInfinite) {
    width = maxWidth;
  } else {
    width = size!.width!;
  }
  if (size?.height != null && size!.height!.isInfinite) {
    height = top + height;
  }else {
    height = size!.height!;
  }
  actualSize = PrinterSize(width, height);
}