Jeff, I respectfully disagree.
By default 100% height (and width for that matter) means 100% of the parent height. We have to also factor in any borders / padding / margin depending on the box model of the respective elements.
It might happen that a given parent is not set to be 100% of its respective parent and so on and so forth, so even if we make our controls stretch / fit their parent, they still won't be as stretchy as needed due to the way CSS works.
One other similar case is when you have height 100% and margin top.
Then come some really interesting cases ( the part I am referring to as "tricky") -- for the sake of argument, let's assume we get the dimensions right on page load. Say we extend a given multipage to fit, say to all available space. Then at some point in time we change the parent -- be it a new element is added, or something else changes with effectively changes the available space. How do our controls get notified about that? Clearly we can't monitor everything that's happening... We do have client side repaint method that takes cares of some cases, but not all...
Let's for a moment forget what's not possible, what's hard, what's tricky and so on. Let's start with a clean slate and look things from another perspective.
What if we didn't say this element should be that much percent of its parent, but instead we had the parent enforce dimensions to its children? Wouldn't that make more sense?
One other reason why this is a better idea is because component vendors do not control (can not modify the styles of) elements they don't own (outside of their respective components). But when something is placed inside a vendors component, well... different rules apply.
What I am trying to say is, that if you had a "thin" layout component that let you align / distribute its children in a way you like, would that suffice? In traditional desktop / application development it would be called Hbox, HorizontalLaout, Flexbox, grid etc... In css terms it's either flexbox or grid, depending on the exact requirements.
Currently we do not offer such component, true, but it doesn't mean we can't make one.
And lastly, but not least, if you share more details to your project, perhaps we could offer you and ad-hoc solution. Or if you are willing to, we could include you in the trials for this new control, should we make one. (And clearly we should make one)
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