[css-overflow-3] Deal with transforms, clear out issues.

Author: fantasai

css-overflow-3/Overview.bs

@@ -152,12 +152,17 @@ Scrollable overflow</h3>
 			all line boxes directly contained by the box
 		<li>
 			the border boxes
-			of all boxes for which it is the containing block
-			(accounting for transforms as described below).
+			of all boxes for which it is the containing block,
+			accounting for transforms by projecting each box onto
+			the plane of the element that establishes its <a>3d-rendering context</a>.
+			[[!CSS-TRANSFORMS-1]]
+
+			Issue: Is this description of handling transforms
+			sufficiently accurate?
 
 		<li>
 			the <a>scrollable overflow regions</a> of all of the above boxes
-			(accounting for transforms as described below),
+			(accounting for transforms as described above),
 			provided they themselves have ''overflow: visible''
 			(i.e. do not themselves trap the overflow)
 			and that overflow is not already clipped
@@ -189,67 +194,6 @@ Scrollable overflow</h3>
 		http://software.hixie.ch/utilities/js/live-dom-viewer/?%3C!DOCTYPE%20html%3E%0A%3Cstyle%3E%0A%20%20div%20%7B%20height%3A%2050px%3B%20overflow%3A%20scroll%3B%20border%3A%20solid%3B%20position%3A%20relative%3B%7D%0A%20%20p%20%7B%20margin%3A%2025px%3B%20background%3A%20red%3B%20%7D%0A%20%20q%20%7B%20position%3A%20absolute%3B%20background%3A%20blue%3B%20top%3A%2025px%3B%20margin%3A%2025px%3B%20%7D%0A%3C%2Fstyle%3E%0A%3Cdiv%3E%0A%20%20%3Cp%3ETest%20%3Cq%3ETest2%0A%3C%2Fdiv%3E
 	-->
 
-	<p class="issue">
-		The following definition should be rewritten to use
-		the concept of <a href="https://drafts.csswg.org/css-transforms/#3d-rendering-context">3D rendering context</a> [[!CSS3-TRANSFORMS]]
-		and related terms,
-		particularly once those concepts stabilize following changes
-		proposed in the CSS WG meeting on the morning of 2014-01-28.
-
-	Given the following definitions
-	<span class="issue">which belong in [[CSS3-TRANSFORMS]]</span>:
-
-	<dl>
-		<dt><dfn>3d-preserving child</dfn>
-		<dd>
-			A child box <var>B</var> of a containing block <var>C</var>
-			is a 3d-preserving child
-			if it has ''transform-style: preserve-3d''
-			and the user-agent is not required to flatten it
-			based on the <a href="https://www.w3.org/TR/css3-transforms/#transform-style-property">requirements</a> in [[!CSS3-TRANSFORMS]].
-
-		<dt><dfn>non-3d-preserving child</dfn>
-		<dd>
-			A child <var>C</var> of a box <var>P</var> is a non-3d-preserving-child
-			if it is not a <a>3d-preserving child</a>.
-
-		<dt><dfn>3d-preserving descendant</dfn>
-		<dd>
-			Box <var>D</var> is a 3d-preserving descendant of box <var>A</var>
-			if <var>A</var> is an ancestor of D,
-			and <var>D</var> and all of the boxes (if any)
-			in the <a>containing block chain</a> from <var>D</var> to <var>A</var>
-			are <a>3d-preserving child</a> boxes.
-	</dl>
-
-	The <a>scrollable overflow</a> of a box is the union of the following things,
-	all adjusted for transforms <span class="issue">undefined concept!</span> into the box's coordinate space:
-
-	<ul>
-		<li>
-			for the box and all of its <a>3d-preserving descendant</a> boxes:
-			<ul>
-				<li>the box's own padding edge (for the box itself) or border edge (for <a>3d-preserving descendant</a> boxes)</li>
-				<li>the bounds <span class="issue">undefined term!</span> of any text directly in the box</li>
-				<li><span class="issue">MORE HERE!</span>
-			</ul>
-		<li>
-			for all the <a>non-3d-preserving child</a> boxes of the
-			box and its <a>3d-preserving descendant</a> boxes,
-			the scrollable overflow of the box
-		</li>
-	</ul>
-
-	<p class="issue">
-		I wrote this definition off the top of my head,
-		so it can't possibly be right.
-		It's missing tons of pieces!
-
-	<p class="issue">
-		The handling of preserve-3d subtrees here is probably wrong;
-		the elements should probably count
-		only towards the overflow of the element that flattens them.
-
 	Note that the <a>scrollable overflow rectangle</a> is a always rectangle
 	in the box's own coordinate system, but might be non-rectangular
 	in other coordinate systems due to transforms [[CSS3-TRANSFORMS]].