More spread clarification

Author: fantasai

css3-background/Overview.html

@@ -3720,9 +3720,9 @@ <h3 id=the-box-shadow><span class=secno>6.2. </span>The &lsquo;<a
    <li>The second length is the vertical offset. A positive value offsets the
     shadow down, a negative one up.
 
-   <li>The third length is a blur value. Negative values are not allowed. If
-    the blur value is zero, the shadow's edge is sharp. Otherwise, the larger
-    the value, the more the shadow's edge is blurred. See below.
+   <li>The third length is a blur distance. Negative values are not allowed.
+    If the blur value is zero, the shadow's edge is sharp. Otherwise, the
+    larger the value, the more the shadow's edge is blurred. See below.
 
    <li>The fourth length is a spread distance. Positive values cause the
     shadow shape to expand in all directions by the specified radius.
@@ -3754,26 +3754,26 @@ <h3 id=the-box-shadow><span class=secno>6.2. </span>The &lsquo;<a
    class=property>border-image</code></a>&rsquo; does not affect the shape of
    the box-shadow.
 
-  <p>If a spread distance is defined, the shadow is expanded outward by an
-   operation equivalent to applying the absolute value of the spread value as
-   a blur operation as defined below and thresholding the result such that
-   for a positive spread radius all non-transparent pixels are given the full
-   shadow color and for a negative spread radius all non-opaque pixels are
-   made transparent. The UA may approximate this operation by taking an
-   outward outset of the specified amount normal to the original shadow
-   perimeter. Alternatively the UA may approximate the transformed shadow
-   perimeter shape by outsetting (insetting, for inner shadows) the shadow's
-   straight edges by the spread distance and increasing (decreasing, for
-   inner shadows) and flooring at zero the corner radii by the same amount.
-   (The UA may even combine these methods, using one method for outer shadows
-   and another for inner ones.) For corners with a zero border-radius,
-   however, the corner must remain sharp&#8212;the operation is equivalent to
-   scaling the shadow shape. In any case, the effective width and height of
-   the shadow shape is floored at zero. (A zero-sized shadow shape would
-   cause an outer shadow to disappear, and an inner shadow to cover the
-   entire padding-box.)
-
-  <p>A positive blur value indicates that the resulting shadow should be
+  <p>If a spread distance is defined, the shadow is expanded outward or
+   contracted inward by an operation equivalent to applying twice the
+   absolute value of the spread value to a blur operation as defined below
+   and thresholding the result such that for a positive spread distance all
+   non-transparent pixels are given the full shadow color and for a negative
+   spread distance all non-opaque pixels are made transparent. The UA may
+   approximate this operation by taking an outward outset of the specified
+   amount normal to the original shadow perimeter. Alternatively the UA may
+   approximate the transformed shadow perimeter shape by outsetting
+   (insetting, for inner shadows) the shadow's straight edges by the spread
+   distance and increasing (decreasing, for inner shadows) and flooring at
+   zero the corner radii by the same amount. (The UA may even combine these
+   methods, using one method for outer shadows and another for inner ones.)
+   For corners with a zero border-radius, however, the corner must remain
+   sharp&#8212;the operation is equivalent to scaling the shadow shape. In
+   any case, the effective width and height of the shadow shape is floored at
+   zero. (A zero-sized shadow shape would cause an outer shadow to disappear,
+   and an inner shadow to cover the entire padding-box.)
+
+  <p>A positive blur distance indicates that the resulting shadow should be
    blurred, such as by a Gaussian filter. The exact algorithm is not defined;
    however for a long, straight shadow edge, this should create a color
    transition the length of the blur distance that is perpendicular to and

css3-background/Overview.src.html

@@ -2687,7 +2687,7 @@ <h3 id="the-box-shadow">The 'box-shadow' property</h3>
   <li>The second length is the vertical offset. A positive value
   offsets the shadow down, a negative one up.
 
-  <li>The third length is a blur value. Negative values are not
+  <li>The third length is a blur distance. Negative values are not
   allowed. If the blur value is zero, the shadow's edge is sharp.
   Otherwise, the larger the value, the more the shadow's edge is
   blurred. See below.
@@ -2721,12 +2721,12 @@ <h3 id="the-box-shadow">The 'box-shadow' property</h3>
 the shadow shape is rounded in the same way. The 'border-image' does not
 affect the shape of the box-shadow.
 
-<p>If a spread distance is defined, the shadow is expanded outward by
-an operation equivalent to applying the absolute value of the spread
-value as a blur operation as defined below and thresholding the result
-such that for a positive spread radius all non-transparent pixels are
-given the full shadow color and for a negative spread radius all
-non-opaque pixels are made transparent.
+<p>If a spread distance is defined, the shadow is expanded outward or
+contracted inward by an operation equivalent to applying twice the
+absolute value of the spread value to a blur operation as defined below
+and thresholding the result such that for a positive spread distance all
+non-transparent pixels are given the full shadow color and for a
+negative spread distance all non-opaque pixels are made transparent.
 The UA may approximate this operation by taking an outward outset of the
 specified amount normal to the original shadow perimeter. Alternatively
 the UA may approximate the transformed shadow perimeter shape by
@@ -2741,7 +2741,7 @@ <h3 id="the-box-shadow">The 'box-shadow' property</h3>
 floored at zero. (A zero-sized shadow shape would cause an outer shadow
 to disappear, and an inner shadow to cover the entire padding-box.)
 
-<p>A positive blur value indicates that the resulting shadow should
+<p>A positive blur distance indicates that the resulting shadow should
 be blurred, such as by a Gaussian filter. The exact algorithm is not
 defined; however for a long, straight shadow edge, this should create
 a color transition the length of the blur distance that is perpendicular