initial take on allowing degenerate shapes

Author: astearns

css-shapes-1/Overview.bs

@@ -153,9 +153,9 @@ Relation to the box model and float behavior</h2>
 	A reduced <a>float area</a> may have no effect
 	on some line boxes
 	that would normally be affected by the float.
-	An <dfn>empty float area</dfn>
-	(where the shape encloses no area)
-	has no effect on line boxes.
+	If a shape does not enclose any area, 
+	the shape’s edges are still used 
+	to define the <a>float area</a>.
 
 	A <a>float area</a> defined by a shape
 	may reduce the normal <a>float area</a> on all sides,
@@ -223,18 +223,34 @@ Relation to the box model and float behavior</h2>
 
 	<div class="example">
 
-		A shape with no extent will create
-		a <a>float area</a> with no extent.
-		Because <a>wrapping</a> only considers the <a>float area</a>,
-		either shape below applied to a float
-		will allow inline content
-		to flow through all of the float's box.
+		A shape that does not enclose any area
+		still has edges that contribute to the <a>float area</a>.
 
+		This inset shape is a vertical line positioned 
+		at the midpoint of the reference box. 
+		This midpoint edge is used as the edge 
+		of the float area for wrapping content.
 		<pre><code>
-			shape-outside: inset(50% 50% 50% 50%);
-			shape-outside: inset(150% 150% 0% 0%);
-		</code>
-		</pre>
+			shape-outside: inset(0% 50% 0% 50%);
+		</code></pre>
+
+		If inset values add up to more than the width, 
+		[[css-backgrounds-3#corner-overlap]] rules are used to determine 
+		the edges of the rectangle. 
+		This shape results in a vertical edge 
+		25% from the left side of the reference box.
+		<pre><code>
+			shape-outside: inset(0% 150% 50% 0%);
+		</code></pre>
+
+		If the shape is only a horizontal line, 
+		then it is an empty float area and has no effect on wrapping. 
+		Note that in this example shape-margin must be 0px 
+		(otherwise the line would expand to enclose an area).
+		<pre><code>
+			shape-outside: inset(50% 0% 0% 50%);
+			shape-margin: 0px;
+		</code></pre>
 	</div>
 
 	<div class="example">
@@ -350,9 +366,11 @@ Supported Shapes</h3>
 			A pair of insets in either dimension
 			that add up to more than the used dimension
 			(such as left and right insets of 75% apiece)
-			define a shape enclosing no area.
-			For this specification,
-			this results in an <a>empty float area</a>.
+			use the [[css-backgrounds-3#corner-overlap]] rules 
+			to proportionally reduce the inset effect to 100%. 
+			This will result in a shape edge positioned 
+			within the reference box 
+			(at 50%, in the case of two 75% inset values). 
 
 		</dd>
 		<dt><dfn>circle()</dfn> =
@@ -365,9 +383,6 @@ Supported Shapes</h3>
 					<strong>r</strong>, the radius
 					of the circle.
 					Negative values are invalid.
-					A radius of zero defines a shape
-					enclosing no area,
-					which results in an <a>empty float area</a>.
 					A percentage value here
 					is resolved from the used width and height
 					of the <a>reference box</a> as <br>
@@ -393,9 +408,6 @@ Supported Shapes</h3>
 					of the ellipse,
 					in that order.
 					Negative values for either radius are invalid.
-					If either radius is zero this defines a shape
-					enclosing no area,
-					which results in an <a>empty float area</a>.
 					Percentage values here are resolved
 					against the used width (for the rx value)
 					and the used height (for the ry value)
@@ -433,13 +445,6 @@ Supported Shapes</h3>
 			by connecting the last vertex
 			with the first vertex of the list.
 
-			At least three vertices are required
-			to define a polygon with an area.
-			This means that (for this specification)
-			polygons with less than three vertices
-			(or with three or more vertices
-			arranged to enclose no area)
-			result in an <a>empty float area</a>.
 		</dd>
 		<dt><dfn>path()</dfn> = 
 			path( [<<'fill-rule'>>,]? <<string>> )
@@ -660,7 +665,7 @@ Shapes from Image</h2>
 	is greater than the 'shape-image-threshold' value.
 	The absence of any pixels with an alpha value
 	greater than the specified threshold
-	results in an <a>empty float area</a>.
+	results in an empty float area that will not affect wrapping.
 	If the 'shape-image-threshold' is not specified,
 	the initial value to be considered is 0.0.
 
@@ -993,16 +998,17 @@ Expanding a Shape: the 'shape-margin' property</h3>
 	that includes all the points
 	that are the 'shape-margin' distance outward
 	in the perpendicular direction
-	from a point on the underlying shape.
+	from a point on the underlying shape. 
+	This includes any edge or line sections 
+	from the underlying shape.
 	Note that at points where
 	a perpendicular is not defined
-	(e.g. sharp points)
+	(e.g. sharp points or line ends)
 	take all points
 	on the circle centered at the point
 	and with a radius of 'shape-margin'.
 	This property takes only non-negative values.
 
-
 	<pre class='propdef'>
 		Name: shape-margin
 		Value: <<length-percentage>>
@@ -1076,6 +1082,8 @@ Expanding a Shape: the 'shape-margin' property</h3>
 Acknowledgments</h2>
 
 	This specification is made possible by input from
+    Tab Atkins Jr.,
+	Amelia Bellamy-Royds,
 	Andrei Bucur,
 	Alexandru Chiculita,
 	Boris Chiou,
@@ -1102,6 +1110,7 @@ Acknowledgments</h2>
 	Peter Sorotokin,
 	Bear Travis,
 	Eugene Veselov,
+	Brad Werth,
 	Stephen Zilles
 	and the CSS Working Group members.
 
@@ -1117,6 +1126,7 @@ Since <a href="https://www.w3.org/TR/2014/CR-css-shapes-1-20140320/">March 20th
 		<li>Added handling of negative margins for margin-box</li>
 		<li>Added clarifications to shape-margin examples</li>
 		<li>Added margin=0 case for margin-box shape</li>
+		<li>Changed rules about degenerate shapes to use shape edges</li>
 	</ul>
 
 <h3 class="no-num" id="20140211">

css-shapes-1/issues-cr-20141015.txt

@@ -73,9 +73,9 @@ Response: https://github.com/w3c/csswg-drafts/issues/1271#issuecomment-542407652
 Closed:   Invalid
 ----
 Issue 11.
-Summary:  
-From:     
-Comment:  
-Response: 
-Closed:   
+Summary:  [css-shapes-1] Degenerate polygons with positive shape-margin
+From:     Brad Werth
+Comment:  https://github.com/w3c/csswg-drafts/issues/2375
+Response: https://github.com/w3c/csswg-drafts/issues/2375#issuecomment-407819143
+Closed:   Accepted