Remove support for segment-completing close path

Segment-completing close path commands, where coordinates are omitted
and implicitly replaced with the initial point of the subpath,
lack implementations and have been removed from the spec.

Discussed in #385

master/changes.html

@@ -433,10 +433,6 @@ <h3 id="coords">Coordinate Systems, Transformations and Units chapter (owner: Bo
 <h3 id="paths">Paths chapter (owner: ericwilligers)</h3>
 
 <ul>
-  <li>Allow <strong>Z</strong> or <strong>z</strong> to fill in
-    missing path coordinate data in the previous command with the
-    coordinate of the initial point in the subpath.</li>
-
   <li>Define <a>'path'</a>, <a>'polygon'</a> and <a>'polyline'</a> elements with no data set (empty or zero valid commands) to not render.</li>
 
   <!--

master/paths.html

@@ -340,33 +340,13 @@ <h3 id="PathDataMovetoCommands">The <strong>"moveto"</strong> commands</h3>
 <h3 id="PathDataClosePathCommand">The <strong>"closepath"</strong> command</h3>
 
 <p>The "closepath" (<strong>Z</strong> or <strong>z</strong>)
-  must end the current subpath by connecting it back to its <a>initial point</a>
-  in either of two ways:
+  ends the current subpath by connecting it back to its <a>initial point</a>.
+  An automatic
+  straight line is drawn from the current point to the <a>initial point</a>
+  of the current subpath. This <a>path segment</a> may be of zero
+  length.
 </p>
 
-<ol>
-  <li>
-    If the previous command is <q>complete</q>, that is that all the
-    required coordinate data has been supplied, then an automatic
-    straight line must be drawn from the current point to the <a>initial point</a>
-    of the current subpath. This <a>path segment</a> may be of zero
-    length.
-  </li>
-  <li class='ready-for-wider-review'>
-    If the previous command is a <a href="paths.html#PathDataLinetoCommands">"lineto"</a>,
-    <a href="paths.html#PathDataCubicBezierCommands">"curveto"</a>,
-    <a href="paths.html#PathDataCubicBezierCommands">"smooth curveto"</a>,
-    <a href="paths.html#PathDataQuadraticBezierCommands">"quadratic Bézier curveto"</a>,
-    <a href="paths.html#PathDataQuadraticBezierCommands">"smooth quadratic Bézier curveto"</a>,
-    or <a href="paths.html#PathDataEllipticalArcCommands">"elliptical arc"</a>,
-    that is missing required coordinate data,
-    then this is a <dfn id="TermSegment-CompletingClosePath">segment-completing close path command</dfn>.
-    No additional path segment is generated by the command; instead,
-    the <a>initial point</a> for this subpath must be used
-    in place of each missing <var>(x,y)</var> coordinate to complete the previous segment.
-  </li>
-</ol>
-
 <table class="PathDataTable">
   <tr>
     <th>Command</th>
@@ -386,22 +366,6 @@ <h3 id="PathDataClosePathCommand">The <strong>"closepath"</strong> command</h3>
   </tr>
 </table>
 
-<p class="note">
-  SVG 2 adds the ability to fill in missing coordinate data with
-  the <strong>Z</strong> or <strong>z</strong> command to avoid the
-  need to add a zero length (or very short in the case of relative
-  paths with rounding errors) <a>path segment</a> to close a subpath. This
-  can effect the number of markers drawn and their orientation at
-  the beginning/end of a closed subpath.
-</p>
-<p class="annotation">
-  The use of <strong>Z</strong> or <strong>z</strong> to replace
-  missing coordinate data with the coordinate of the <a>initial point</a> in
-  a subpath was resolved at the
-  <a href="http://www.w3.org/2015/02/12-svg-minutes.html#item04">Sydney
-    (2015)</a> meeting.
-</p>
-
 <p>A <dfn id="TermClosedSubpath">closed subpath</dfn> must be closed with a
 "closepath" command, this "joins" the first and last <a>path segments</a>.
 Any other path is an <dfn id="TermOpenSubpath">open subpath</dfn>.</p>
@@ -421,39 +385,6 @@ <h3 id="PathDataClosePathCommand">The <strong>"closepath"</strong> command</h3>
 other command, then the next subpath must start at the same <a>initial point</a>
 as the current subpath.</p>
 
-<p>Examples:</p>
-<ul>
-  <li>
-    m 100,100 50,0 0,50 z:
-
-    Implicit <strong>l</strong> command complete, <strong>z</strong> causes a
-    straight line to be drawn resulting in a closed triangular path.
-  </li>
-  <li>
-    m 100,100 a 50,50 0 0 1 100,0 z:
-
-    <strong>a</strong> command complete, <strong>z</strong> causes a
-    straight line to be drawn resulting in a closed semi-circular path.
-  </li>
-  <li>
-    m 100,100 a 50,50 0 0 1 100,0 50,50 0 0 1 z:
-
-    Second set of coordinates for the <strong>a</strong> command
-    missing final point, <strong>z</strong> causes <a>initial point</a> to
-    be used as final point resulting in a closed circular path.
-  </li>
-  <li>
-    m 100,100 a 50,50 0 0 1 100,0 c z:
-
-    <strong>c</strong> command missing three coordinates,
-    <strong>z</strong> causes <a>initial point</a> to be used as coordinate
-    data for all <strong>c</strong> coordinates resulting in a
-    closed semi-circle. Visually <strong>c</strong>
-    <strong>z</strong> is the same as <strong>z</strong> but may be
-    useful in animating path data.
-  </li>
-</ul>
-
 <h3 id="PathDataLinetoCommands">The <strong>"lineto"</strong> commands</h3>
 
 <p>The various "lineto" commands draw straight lines from the
@@ -833,13 +764,13 @@ <h3 id="PathDataBNF">The grammar for path data</h3>
     | elliptical_arc
 
 moveto::=
-    ( "M" | "m" ) wsp* coordinate_pair_sequence wsp* closepath?
+    ( "M" | "m" ) wsp* coordinate_pair_sequence
 
 closepath::=
     ("Z" | "z")
 
 lineto::=
-    ("L"|"l") wsp* (coordinate_pair_sequence | closepath)
+    ("L"|"l") wsp* coordinate_pair_sequence
 
 horizontal_lineto::=
     ("H"|"h") wsp* coordinate_sequence
@@ -848,35 +779,31 @@ <h3 id="PathDataBNF">The grammar for path data</h3>
     ("V"|"v") wsp* coordinate_sequence
 
 curveto::=
-    ("C"|"c") wsp* (curveto_coordinate_sequence | (coordinate_pair_sequence? closepath))
+    ("C"|"c") wsp* curveto_coordinate_sequence
 
 curveto_coordinate_sequence::=
     coordinate_pair_triplet
     | (coordinate_pair_triplet comma_wsp? curveto_coordinate_sequence)
 
 smooth_curveto::=
-    ("S"|"s") wsp* (smooth_curveto_coordinate_sequence
-    | (coordinate_pair_sequence? closepath))
+    ("S"|"s") wsp* smooth_curveto_coordinate_sequence
 
 smooth_curveto_coordinate_sequence::=
     coordinate_pair_double
     | (coordinate_pair_double comma_wsp? smooth_curveto_coordinate_sequence)
 
 quadratic_bezier_curveto::=
-    ("Q"|"q") wsp*
-    (quadratic_bezier_curveto_coordinate_sequence | (coordinate_pair_sequence? closepath))
+    ("Q"|"q") wsp* quadratic_bezier_curveto_coordinate_sequence
 
 quadratic_bezier_curveto_coordinate_sequence::=
     coordinate_pair_double
     | (coordinate_pair_double comma_wsp? quadratic_bezier_curveto_coordinate_sequence)
 
 smooth_quadratic_bezier_curveto::=
-    ("T"|"t") wsp* (coordinate_pair_sequence | closepath)
+    ("T"|"t") wsp* coordinate_pair_sequence
 
 elliptical_arc::=
-    ( "A" | "a" ) wsp*
-    (elliptical_arc_argument_sequence
-    | (elliptical_arc_argument_sequence? elliptical_arc_closing_argument))
+    ( "A" | "a" ) wsp* elliptical_arc_argument_sequence
 
 elliptical_arc_argument_sequence::=
     elliptical_arc_argument
@@ -886,10 +813,6 @@ <h3 id="PathDataBNF">The grammar for path data</h3>
     number comma_wsp? number comma_wsp? number comma_wsp
     flag comma_wsp? flag comma_wsp? coordinate_pair
 
-elliptical_arc_closing_argument::=
-    number comma_wsp? number comma_wsp? number comma_wsp
-    flag comma_wsp? flag comma_wsp? closepath
-
 coordinate_pair_double::=
     coordinate_pair comma_wsp? coordinate_pair