[css2] Authors should put content property in @media, added limitation (no postion, float) to :before and :after, markers have no margins, added @media to examples where pertinent, height propety may be set for before/after content

--HG--
extra : convert_revision : svn%3A73dc7c4b-06e6-40f3-b4f7-9ed1dbc14bfc/trunk%401235

Author: ianbjacobs

css2/generate.src

@@ -62,9 +62,6 @@ from the element to which they are attached.</p>
 specify content, and the style of that content, before and after an
 element's <a href="conform.html#doctree">document tree</a> content.
 
-<!-- Do they allow the position and float properties? Probably
-not. Must say so. -IJ -->
-
 <P>The :before and :after pseudo-elements elements allow 
 values of the <span class="propinst-display">'display'</span>
 property as follows:
@@ -85,10 +82,19 @@ was 'inline'.
 </ul>
 
 <div class="note"><P>
-<em><strong>Note.</strong>Other values may be permitted in
+<em><strong>Note.</strong> Other values may be permitted in
 future levels of CSS.</em>
 </div>
 
+
+<!-- Proposed -IJ --> 
+
+<P>User agents must ignore the following properties with :before and
+:after pseudo-elements: <span
+class="propinst-position">'position'</span>, <span
+class="propinst-float">'float'</span>, list properties, and table
+properties.
+
 <P>The (inline or block) box created for the generated content
 precedes (or follows for :after) any box generated by the element's
 content. For block-level elements, the containing block established by
@@ -159,17 +165,13 @@ class="value-inst-string"><strong>&lt;string&gt;</strong></span></span>
 <dt><span class="index-inst" title="&lt;uri&gt;"><span
 class="value-inst-uri"><strong>&lt;uri&gt;</strong></span></span>
 <dd>The value is a URI that designates an external resource.
+If a user agent cannot support the resource because of the
+media types it supports, it must ignore the resource.
 <strong>Note.</strong> CSS2 offers no
 mechanism to change the size of the embedded object, or to provide a
 textual description, like the "alt" or "longdesc" attributes do for
 images in HTML. This may change in future levels of CSS.
 
-<!-- Specify what media types are allowed? Media type must match
-current medium (or current @media?): aural rendering MUST ignore an
-image, etc. Text/html must be ignored by all. For efficiency, allow
-"visual-url(URL)" (or "visual(url())" or some other syntax)?  26/2/98
--->
-
 <dt><span class="index-inst" title="&lt;counter&gt;"><span
 class="value-inst-counter"><strong>&lt;counter&gt;</strong></span></span>
 <dd><a href="syndata.html#counter">Counters</a> have the form
@@ -223,7 +225,6 @@ is <em>not</em> replaced by a space).
 -->
 </dl>
 
-
 <div class="example">
 <p>This rule inserts the text of the HTML "alt" attribute before the
 image. If the image is not displayed, the reader will still see the
@@ -234,6 +235,14 @@ IMG:before {content: attr(alt)}
 </pre>
 </div>
 
+<P>Authors should put <span class="propinst-content">'content'</span>
+declarations in <span class="index-inst" title="@media"><a
+href="media.html@at-media-rule">@media</a></span> rules when
+the content requires media consideration. For instance, literal
+text may be used for any media group, but images only
+apply to the visual, bitmap media groups, and sound files only
+apply to the aural media group.
+
 <div class=note>
 <p><em><strong>Note.</strong> In future levels of CSS, the <span
 class="propinst-content">'content'</span> property may accept
@@ -476,7 +485,7 @@ the counter is set to on each occurrence of the element. The default
 is 0.
 
 <p>If <span
-class="propinst-counter-increments">'counter-increments'</span> refers
+class="propinst-counter-increment">'counter-increment'</span> refers
 to a counter that is not in the <a href="#scope">scope</a> of any
 <span class="propinst-counter-reset">'counter-reset'</span>, the
 counter is assumed to have been reset to 0 by the root element.
@@ -660,11 +669,7 @@ content (i.e., one <a href="visuren.html#line-box">line box</a>), so
 they are not as flexible as <a href="visuren.html">floats</a>, which
 may be used to align entire blocks horizontally.
 
-<P>Marker boxes have padding, borders, and margins.
-
-<!-- Do they have margins? I would say no except that
-abs. positioned boxes now have margins, too -IJ -->
-<!-- I'd say no, too. BB -->
+<P>Marker boxes have padding and borders, but no margins.
 
 <P>To create a marker box for :before or :after content, the <span
 class="propinst-display">'display'</span> property must be given the
@@ -688,9 +693,11 @@ principal box.
 specified with the <span
 class="propinst-vertical-align">'vertical-align'</span> property.
 
-<p>The height of the :before marker and of the first line box of the
-principal box is computed as if they were a single line
-box. Analogously for the :after marker and the last line box.
+<p>By default, the height of the :before marker and of the first line
+box of the principal box is computed as if they were a single line
+box. Analogously for the :after marker and the last line box. However,
+the <span class="propinst-height">'height'</span> property may be
+specified for a marker box.
 
 <P>The width of a marker box defaults to the natural width of its
 content, but may be specified with the <span
@@ -699,9 +706,10 @@ marker box's content is greater than the specified width, the <span
 class="propinst-overflow">'overflow'</span> property specifies
 overflow behavior. Marker boxes may overlap principal boxes.
 
-<p>If the 'width' is not 'auto', and is larger than the natural width,
-the <span class="propinst-text-align">'text-align'</span> property
-determines the alignment of the text in the marker box.
+<p>If the <span class="propinst-width">'width'</span> is not 'auto',
+and is larger than the natural width, the <span
+class="propinst-text-align">'text-align'</span> property determines
+the alignment of the text in the marker box.
 
 <P>The <span class="propinst-marker-offset">'marker-offset'</span>
 property specifies the horizontal offset between a marker box and the
@@ -711,9 +719,10 @@ href="visuren.html#border-edge">border edges</a>.
 <p class="note">[Is this offset kept constant, even if
 'overflow:visible'? I would say it gets smaller. BB]
 
-<P>When the <span class="propinst-marker">'marker'</span> property is
-set for content generated by an element with 'display: list-item', a
-marker box generated for ':before' replaces the normal list item marker.
+<P>When the <span class="propinst-display">'display'</span> property
+has the value 'marker' for content generated by an element with
+'display: list-item', a marker box generated for ':before' replaces
+the normal list item marker.
 
 <div class="example"><P>
 The following example illustrates how markers may
@@ -797,12 +806,14 @@ list items. This document:</p>
 &lt;HTML&gt;
   &lt;HEAD&gt;
     &lt;STYLE type="text/css"&gt;
-      LI:before { 
-	   display: marker;
-	   content: url(smiley.gif);
-      LI:after {
-	   display: marker;
-	   content: url(sad.gif);
+      @media screen, print {
+         LI:before { 
+   	      display: marker;
+	      content: url(smiley.gif);
+         LI:after {
+	      display: marker;
+   	      content: url(sad.gif);
+         }
       }
     &lt;/STYLE&gt;
   &lt;/HEAD&gt;
@@ -835,13 +846,16 @@ The following document:</p>
   &lt;HEAD&gt;
     &lt;STYLE type="text/css"&gt;
       P { margin-left: 12 em; }
-      P.Note:before         { 
-	   display: marker;
-	   content: url(note.gif) "Note " numeric(note-counter) ":";
-           counter-increment: note-counter;
-           text-align: left;
-           width: 10em;
-      }
+      @media screen, print {
+         P.Note:before         { 
+  	      display: marker;
+	      content: url(note.gif) 
+                       "Note " numeric(note-counter) ":";
+              counter-increment: note-counter;
+              text-align: left;
+              width: 10em;
+         }
+     }
     &lt;/STYLE&gt;
   &lt;/HEAD&gt;
   &lt;BODY&gt;