Why does Row give it's children infinite width instead of its remaining space?

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1

I’m trying to understand the layout algorithm and the rationale behind it. It appears that Row gives a width constraint of infinity to its children and this causes certain issues. I wonder, why does it not give its remaining width instead? Eg, if it was constrained with 600 px, and had 3 children, it could:

  • give first a max width of 600.
  • first child uses 100
  • give the second 600-100 = 500
  • repeat for other children…
2

Actually, a Row always gives its unconstrained children infinite width constraints, even if the Row itself is in a bounded space. It does this so children can size themselves to their natural width.

The issue only happens when a child (like a TextField or another scrollable view) also wants infinite width. To force a child to only take up the remaining space of the Row, you have to wrap that child in an Expanded or Flexible widget!

3

Maybe the only answer is that it “is what it is”, but it doesn’t make sense to me. If the Row is constrained to a max width of, say, 600px, it’s not going to be able to render wider than 600px, so why not pass that “max width” down, so its children at least of a chance to try to adapt to it. That seems like the point of a max width constraint!

4

Well the layout algorithm is explained in the Row docs:

Also there is a lot of documentation on the constraints and sizing in general here:

But I couldn’t find the exact rationel behind it. I think its meanly because its used for flexible layout.