Patrick Walton 5b36d211b4 Add an implementation of the core float and clear placement logic in layout ... 2020, not yet wired to the rest of layout. This commit implements an object that handles the 10 rules in CSS 2.1: https://www.w3.org/TR/CSS2/visuren.html#float-position The implementation strategy is that of a persistent balanced binary search tree of float bands. Binary search trees are commonly used for implementing float positioning; e.g. by WebKit. Persistence enables each object that interacts with floats to efficiently contain a snapshot of the float list at the time that object was laid out. That way, incremental layout can invalidate and start reflow at any point in a containing block. This commit features extensive use of [QuickCheck](https://github.com/BurntSushi/quickcheck) to ensure that the rules of the CSS specification are followed. Because this is not yet connected to layout, floats will not actually be laid out in Web pages yet. Note that unit tests as set up in Servo currently require types that they access to be public. Therefore, some internal layout 2020 types that were previously private have been made public. This is somewhat unfortunate. Part of #25167.		2020-07-20 12:42:34 -07:00
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floats.rs	Add an implementation of the core float and clear placement logic in layout	2020-07-20 12:42:34 -07:00