paint method

void paint (Canvas canvas, Rect rect, { @required Iterable<double> rows, @required Iterable<double> columns })

Paints the border around the given Rect on the given Canvas, with the given rows and columns.

Uniform borders are more efficient to paint than more complex borders.

The rows argument specifies the vertical positions between the rows, relative to the given rectangle. For example, if the table contained two rows of height 100.0 each, then rows would contain a single value, 100.0, which is the vertical position between the two rows (relative to the top edge of rect).

The columns argument specifies the horizontal positions between the columns, relative to the given rectangle. For example, if the table contained two columns of height 100.0 each, then columns would contain a single value, 100.0, which is the vertical position between the two columns (relative to the left edge of rect).

The verticalInside border is only drawn if there are at least two columns. The horizontalInside border is only drawn if there are at least two rows. The horizontal borders are drawn after the vertical borders.

The outer borders (in the order top, right, bottom, left, with left above the others) are painted after the inner borders.

The paint order is particularly notable in the case of partially-transparent borders.

Implementation 

void paint(Canvas canvas, Rect rect, {
  @required Iterable<double> rows,
  @required Iterable<double> columns,
}) {
  // properties can't be null
  assert(top != null);
  assert(right != null);
  assert(bottom != null);
  assert(left != null);
  assert(horizontalInside != null);
  assert(verticalInside != null);

  // arguments can't be null
  assert(canvas != null);
  assert(rect != null);
  assert(rows != null);
  assert(rows.isEmpty || (rows.first >= 0.0 && rows.last <= rect.height));
  assert(columns != null);
  assert(columns.isEmpty || (columns.first >= 0.0 && columns.last <= rect.width));

  if (columns.isNotEmpty || rows.isNotEmpty) {
    final Paint paint = Paint();
    final Path path = Path();

    if (columns.isNotEmpty) {
      switch (verticalInside.style) {
        case BorderStyle.solid:
          paint
            ..color = verticalInside.color
            ..strokeWidth = verticalInside.width
            ..style = PaintingStyle.stroke;
          path.reset();
          for (double x in columns) {
            path.moveTo(rect.left + x, rect.top);
            path.lineTo(rect.left + x, rect.bottom);
          }
          canvas.drawPath(path, paint);
          break;
        case BorderStyle.none:
          break;
      }
    }

    if (rows.isNotEmpty) {
      switch (horizontalInside.style) {
        case BorderStyle.solid:
          paint
            ..color = horizontalInside.color
            ..strokeWidth = horizontalInside.width
            ..style = PaintingStyle.stroke;
          path.reset();
          for (double y in rows) {
            path.moveTo(rect.left, rect.top + y);
            path.lineTo(rect.right, rect.top + y);
          }
          canvas.drawPath(path, paint);
          break;
        case BorderStyle.none:
          break;
      }
    }
  }
  paintBorder(canvas, rect, top: top, right: right, bottom: bottom, left: left);
}