[css-text-decor] Try to make text decoration positioning text more clear

--HG--
extra : rebase_source : 6b3ac91346c9c520c9d5fc2c9f097eaeda74e1f5

Author: tabatkins

css-text-decor/Overview.html

@@ -1047,22 +1047,21 @@ <h3 id=line-position><span class=secno>2.7. </span> Determining the
   <p>Since line decorations can span elements with varying font sizes and
    vertical alignments, the best position for a line decoration is not
    necessarily the ideal position dictated by the <a
-   href="#decorating-box"><i>decorating box</i></a>. In determining the
-   position of text decoration lines, user agents must consider, for each <a
-   href="#decorating-box"><i>decorating box</i></a>, the “ideal”
-   positions of such line decorations per fragment of the <a
-   href="#decorating-box"><i>decorating box</i></a>—or its in-flow inline
-   descendant—that draws the text decoration. However, descendants of the
-   <a href="#decorating-box"><i>decorating box</i></a> that are skipped due
-   to ‘<a href="#text-decoration-skip"><code
+   href="#decorating-box"><i>decorating box</i></a>. Instead, it's
+   calculated, per line, from all text decorated by the <a
+   href="#decorating-box"><i>decorating box</i></a> on that line, the
+   <i>considered text</i>. However, descendants of the <a
+   href="#decorating-box"><i>decorating box</i></a> that are skipped due to
+   ‘<a href="#text-decoration-skip"><code
    class=property>text-decoration-skip</code></a>’, descendant inlines with
    ‘<code class=css>text-decoration-skip: ink</code>’, and any
    descendants that do not participate in the <a
    href="#decorating-box"><i>decorating box</i></a>’s inline formatting
-   context are excluded from consideration.
+   context are excluded from the set of <i>considered text</i>.
 
-  <p> The line decoration positions are then calculated as follows (treating
-   <a href="#underline-left"><i>over</i>-positioned underlines</a> as
+  <p> The line decoration positions are then calculated per set of
+   <i>considered fragments</i> as follows (treating <a
+   href="#underline-left"><i>over</i>-positioned underlines</a> as
    <i>over</i> lines and <a href="#underline-left"><i>under</i>-positioned
    overlines</a> as <i>under</i> lines):
 
@@ -1074,20 +1073,20 @@ <h3 id=line-position><span class=secno>2.7. </span> Determining the
    <dd> Align the line decoration with respect to the highest
     <!-- <i>text-over</i> baseline of the considered fragments. --> <a
     href="http://www.w3.org/TR/css3-writing-modes/#over"><i>over</i></a> edge
-    of the considered fragments’ content boxes.
+    of the <i>considered fragments</i>’ content boxes.
 
    <dt><a href="#underline-alphabetic"><i>alphabetic</i></a> underlines
 
    <dd>
     <p>The alphabetic underline position is calculated by taking the ideal
-     offset (from the alphabetic baseline) of each considered fragment,
-     averaging those, and then using the lowest alphabetic baseline to
-     actually position the line. (Alphabetic baselines can differ between
-     ‘<code class=css>baseline</code>’-aligned boxes if the dominant
-     baseline is non-alphabetic.) To prevent superscripts and subscripts from
-     throwing this position off-kilter, an inline with a non-initial computed
-     ‘<code class=property>vertical-align</code>’ is treated as having
-     the ideal underline position of their parent.
+     offset (from the alphabetic baseline) of each <i>considered
+     fragment</i>, averaging those, and then using the lowest alphabetic
+     baseline to actually position the line. (Alphabetic baselines can differ
+     between ‘<code class=css>baseline</code>’-aligned boxes if the
+     dominant baseline is non-alphabetic.) To prevent superscripts and
+     subscripts from throwing this position off-kilter, an inline with a
+     non-initial computed ‘<code class=property>vertical-align</code>’ is
+     treated as having the ideal underline position of their parent.
 
    <dt>non-alphabetic <a
     href="http://www.w3.org/TR/css3-writing-modes/#under"><i>under</i></a>
@@ -1096,7 +1095,7 @@ <h3 id=line-position><span class=secno>2.7. </span> Determining the
    <dd> Position the line decoration with respect to the lowest
     <!-- <i>text-under</i> baseline of the considered fragments. --> <a
     href="http://www.w3.org/TR/css3-writing-modes/#under"><i>under</i></a>
-    edge of the considered fragments’ content boxes.
+    edge of the <i>considered fragments</i>’ content boxes.
 
    <dt>line-throughs
 
@@ -1105,7 +1104,7 @@ <h3 id=line-position><span class=secno>2.7. </span> Determining the
     descendant with a different computed ‘<code
     class=property>font-size</code>’. (This ensures that the text remains
     effectively “crossed out” despite any font size changes.) For each
-    set of considered fragments with the same ‘<code
+    set of <i>considered fragments</i> with the same ‘<code
     class=property>font-size</code>’, compute an ideal position averaged
     from their direct contents and font metrics (assigning any fragment with
     non-initial ‘<code class=property>vertical-align</code>’ the ideal

css-text-decor/Overview.src.html

@@ -687,19 +687,17 @@ <h3 id="line-position">
   <p>Since line decorations can span elements with varying font sizes and
     vertical alignments, the best position for a line decoration is not
     necessarily the ideal position dictated by the <i>decorating box</i>.
-    In determining the position of text decoration lines,
-    user agents must consider, for each <i>decorating box</i>,
-    the “ideal” positions of such line decorations per fragment
-    of the <i>decorating box</i>&mdash;or its in-flow inline descendant&mdash;that
-    draws the text decoration.
+    Instead, it's calculated, per line, from all text decorated by the <i>decorating box</i> on that line,
+    the <i>considered text</i>.
     However, descendants of the <i>decorating box</i>
     that are skipped due to 'text-decoration-skip',
     descendant inlines with ''text-decoration-skip: ink'',
     and any descendants that do not participate in the <i>decorating box</i>’s inline formatting context
-    are excluded from consideration.
+    are excluded from the set of <i>considered text</i>.
 
   <p>
     The line decoration positions are then calculated
+    per set of <i>considered fragments</i>
     as follows
     (treating <a href="#underline-left"><i>over</i>-positioned underlines</a> as <i>over</i> lines
     and <a href="#underline-left"><i>under</i>-positioned overlines</a> as <i>under</i> lines):
@@ -710,12 +708,12 @@ <h3 id="line-position">
       Align the line decoration with respect to the highest
       <!-- <i>text-over</i> baseline of the considered fragments. -->
       <a href="http://www.w3.org/TR/css3-writing-modes/#over"><i>over</i></a> edge
-      of the considered fragments’ content boxes.
+      of the <i>considered fragments</i>’ content boxes.
 
     <dt><a href="#underline-alphabetic"><i>alphabetic</i></a> underlines
     <dd>
       <p>The alphabetic underline position is calculated by taking
-      the ideal offset (from the alphabetic baseline) of each considered fragment,
+      the ideal offset (from the alphabetic baseline) of each <i>considered fragment</i>,
       averaging those, and then using the lowest alphabetic baseline to actually position the line.
       (Alphabetic baselines can differ between ''baseline''-aligned boxes
        if the dominant baseline is non-alphabetic.)
@@ -728,14 +726,14 @@ <h3 id="line-position">
       Position the line decoration with respect to the lowest
       <!-- <i>text-under</i> baseline of the considered fragments. -->
       <a href="http://www.w3.org/TR/css3-writing-modes/#under"><i>under</i></a> edge
-      of the considered fragments’ content boxes.
+      of the <i>considered fragments</i>’ content boxes.
 
     <dt>line-throughs
     <dd>
       Line-throughs essentially use the same sort of averaging as for alphabetic underlines,
       but recompute the position when drawing across a descendant with a different computed 'font-size'.
       (This ensures that the text remains effectively “crossed out” despite any font size changes.)
-      For each set of considered fragments with the same 'font-size', 
+      For each set of <i>considered fragments</i> with the same 'font-size', 
       compute an ideal position averaged from their direct contents and font metrics
       (assigning any fragment with non-initial 'vertical-align' the ideal position of its parent).
       Position the portion of the line across each decorated fragment at that position.