@@ -116,29 +116,43 @@ This specification does not mandate if and how scroll chaining or overscroll aff
116116implemented. This specification only allows the content author to disable them if any are
117117implemented.</em>
118118119-<dfn>Scroll chaining</dfn> is when scrolling is propagated from one <a>scroll container</a> to an
120-ancestor <a>scroll container</a> following the <a>scroll chain</a>. Typically scroll chaining is
121-performed starting at the event target recursing up the <a>containing block chain</a>. When a
122-<a>scroll container</a> in this chain receives a scroll event or gesture it may act on it and/or
123-pass it up the chain. Chaining typically occurs when the <a>scrollport</a> has reached its boundary.
124-125-A <dfn>scroll chain</dfn> is the order in which scrolling is propagated from one <a>scroll
126-container</a> to another. The <a>viewport</a> participates in <a>scroll chaining</a> as the
127-document's <a>scrollingElement</a>, both regarding placement in the scroll chain as well as adhering
128-to the chaining rules applied to it.
129-130-131-<dfn>Scroll boundary</dfn> refers to when the scroll position of a <a>scroll container</a> reaches
132-the edge of the <a>scrollport</a>. If a [=scroll container=] has no potential to scroll, because it does
133-not <a>overflow</a> in the direction of the scroll or the scroll does not happen in one of its [=scrollable axises=], the element is always considered to be at the
134-scroll boundary.
135-136-<dfn>Boundary default action</dfn> refers to the user-agent-defined <a>default action</a> performed
137-when scrolling against the edge of the <a>scrollport</a>. A <dfn>local boundary default action</dfn>
138-is a <a>boundary default action</a> which is performed on the <a>scroll container</a> without
139-interacting with the page, for example displaying a overscroll UI affordance. Conversely, a
140-<dfn>non-local boundary default action</dfn> interacts with the page, for example scroll chaining or
141-a navigation action.
119+<dfn>Scroll chaining</dfn> is when scrolling is propagated from one <a>scroll container</a>
120+to an ancestor <a>scroll container</a>
121+following the <a>scroll chain</a>.
122+Typically scroll chaining is performed starting at the event target
123+recursing up the <a>containing block chain</a>.
124+When a <a>scroll container</a> in this chain receives a scroll event or gesture
125+it may act on it and/or pass it up the chain.
126+Chaining typically occurs when the <a>scrollport</a> has reached its boundary.
127+128+A <dfn>scroll chain</dfn> is the order in which scrolling is propagated
129+from one <a>scroll container</a> to another.
130+For a given [=scroll container=] and scroll,
131+the next link in its [=scroll chain=]
132+is the nearest ancestor [=scroll container=]
133+in the [=containing block chain=]
134+that is scrollable in the scroll's axis.
135+The <a>viewport</a> participates in <a>scroll chaining</a>
136+as the document's <a>scrollingElement</a>,
137+both regarding placement in the scroll chain
138+as well as adhering to the chaining rules applied to it.
139+140+<dfn>Scroll boundary</dfn> refers to when the scroll position of a <a>scroll container</a>
141+reaches the edge of the <a>scrollport</a>.
142+If a [=scroll container=] has no potential to scroll,
143+because it does not <a>overflow</a> in the direction of the scroll,
144+the element is always considered to be at the scroll boundary.
145+If a [=scroll container=] is not scrollable in the given axis,
146+it doesn't have a [=scroll boundary=] at all in that axis
147+(and won't be part of this scroll's [=scroll chain=].)
148+149+<dfn>Boundary default action</dfn> refers to the user-agent-defined <a>default action</a>
150+performed when scrolling against the edge of the <a>scrollport</a>.
151+A <dfn>local boundary default action</dfn> is a <a>boundary default action</a>
152+which is performed on the <a>scroll container</a> without interacting with the page,
153+for example displaying a overscroll UI affordance.
154+Conversely, a <dfn>non-local boundary default action</dfn> interacts with the page,
155+for example scroll chaining or a navigation action.
142156143157144158@@ -160,6 +174,10 @@ Note: This property should provide guarantees that are, at least, as strong as <
160174for preventing both scroll chaining and overscroll. Doing otherwise would cause content authors to
161175use <a>preventDefault</a> instead.
162176177+178+The 'overscroll-behavior' Shorthand {#overscroll-shorthand}
179+-----------------------------------
180+163181<pre class=propdef>
164182Name: overscroll-behavior
165183Value: [ contain | none | auto | chain ]{1,2}
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