[css2] Small corrections.

Default clip region is size of box itself, not size of containing
block.

--HG--
extra : convert_revision : svn%3A73dc7c4b-06e6-40f3-b4f7-9ed1dbc14bfc/trunk%401569

Author: bert-github

css2/visufx.src

@@ -16,30 +16,32 @@ only presentation.</em>
 content edges of the box. In certain cases, a box may <span
 class="index-def"
 title="overflow|box::overflow"><dfn>overflow</dfn></span>, meaning its
-content lies partly or entirely outside of the containing block:</P>
+content lies partly or entirely outside of the box, e.g.:</P>
 
 <ul>
+<li>A line cannot be broken, causing the line box to be wider than the
+block box.
 
-<li>Content is too wide for the containing block. This may happen when an
+<li>A block-level box is too wide for the containing block. This may
+happen when an
 element's <span class="propinst-width">'width'</span> property has a
 value that causes the generated block box to spill over
-sides of the containing block. An inline replaced element
-(e.g., an image) that has a large <span class="index-inst"
-title="intrinsic width">intrinsic width</span> may also overflow.
+sides of the containing block.
 
 <li>An element's height exceeds an explicit height assigned to the containing
 block (i.e., the containing block's height is determined by the <span
 class="propinst-height">'height'</span> property, not by content
 height).
 
-<li>It is <a href="visuren.html#absolute-positioning">positioned
+<li>A box is <a href="visuren.html#absolute-positioning">positioned
 absolutely</a>.
 
 <li>It has <a href="box.html#margin-properties">negative margins</a>.
 </ul>
 
 <p>Whenever overflow occurs, the <span
-class="propinst-overflow">'overflow'</span> property specifies how a
+class="propinst-overflow">'overflow'</span> property specifies how
+(and whether) a
 box is clipped. The <span class="propinst-clip">'clip'</span> property
 specifies the size and shape of the clipping region.  Specifying a
 small clipping region may cause clipping of otherwise visible
@@ -72,17 +74,18 @@ by the <span class="propinst-clip">'clip'</span> property.
 
 <dt><strong>scroll</strong> 
 
-<dd>This value indicates that if the user agent supports a visible
-scrolling mechanism, that mechanism should be displayed for a box
-whether or not any of its content is clipped. This avoids any problem
-with scrollbars appearing and disappearing in a dynamic
+<dd>This value indicates that the content is clipped and that if the
+user agent uses scrolling mechanism that is visible on the screen
+(such as a scroll bar or a panner), that mechanism should be displayed
+for a box whether or not any of its content is clipped. This avoids
+any problem with scrollbars appearing and disappearing in a dynamic
 environment. When this value is specified and the target medium is
 'print' or 'projection', overflowing content should be printed.
 
 <dt><strong>auto</strong> 
 
 <dd>The behavior of the 'auto' value is user agent-dependent, but
-should cause a scrolling mechanism to appear for overflowing boxes.
+should cause a scrolling mechanism to be provided for overflowing boxes.
 
 </dl>
 
@@ -91,7 +94,7 @@ to 'visible', content may be clipped to a UA's document window by the
 native operating environment.
 
 <div class="example"><P>
-Consider the following example, of a block quotation
+Consider the following example of a block quotation
 (BLOCKQUOTE) that is too big
 for its containing block (established by a DIV). Here is
 the source document:</p>
@@ -111,18 +114,21 @@ generated boxes:
 
 <PRE>
 DIV { width : 100px; height: 100px;
-      border: thin solid red
+      border: thin solid red;
       }
 
 BLOCKQUOTE   { width : 125px; height : 100px;
-      position: absolute;
-      top: 50px; left: 50px; 
+      margin-top: 50px; margin-left: 50px; 
       border: thin dashed black
       }
 
 DIV.attributed-to { text-align : right; }
 </PRE>
 
+<!-- I replaced top and left with margin-top and margin-left, and
+removed postion:absolute. Another way to fix the example is to add
+position:relative to DIV, but that would make the example, longer,
+while this made it shorter. BB -->
 
 <P>The initial value of <span
 class="propinst-overflow">'overflow'</span> is 'visible', so
@@ -151,20 +157,20 @@ class="propinst-clip">'clip'</span> property</h3>
 <p>A <span class="index-def" title="clipping region"><dfn>clipping
 region</dfn></span> defines what portion of an element's <a
 href="conform.html#rendered-content">rendered content</a> is
-visible. By default, the containing block established by the element
-acts as the clipping region for the element's content (i.e., the
-clipping region has the same size as the containing block).  However,
-the clipping region dimensions may be modified by the <span
-class="propinst-clip">'clip'</span> property.
+visible. By default, the clipping region has the same size and shape
+as the element's box(es). However, the clipping region may be
+modified by the <span class="propinst-clip">'clip'</span> property.
 
 <!-- #include src=properties/clip.srb -->
 
-<P>Values have the following meanings:</p>
+<P>The 'clip' property applies to elements that have a <span
+class="propinst-overflow">'overflow'</span> property with a value
+other than 'visible'. Values have the following meanings:</p>
 
 <dl>
 <dt><strong>auto</strong>
 <dd>The clipping region has the same size and location
-as the containing block established by the element.
+as the element's box(es).
 
 <dt><span class="index-def" title="&lt;shape&gt;::definition of"><a
 name="value-def-shape"
@@ -196,11 +202,21 @@ value or 'auto'.  Negative lengths are permitted. The value 'auto'
 means that a given edge of the clipping region will be the same as the
 edge of the element's generated box (i.e., 'auto' means the same as '0'.)
 
-<P> When converted to pixel coordinates, the bottom-right corner is
+<P>When coordinates are rounded to pixel coordinates, care should be
+taken that no pixels remain visible when &lt;left&gt; + &lt;right&gt;
+is equal to the element's width (or &lt;top&gt; + &lt;bottom&gt;
+equals the element's height), and conversely that no pixels remain
+hidden when these values are 0.
+<!-- When converted to pixel coordinates, the bottom-right corner is
 excluded from the clipping rectangle. This rule is necessary to permit
-the definition of zero-width or zero-height rectangles.
+the definition of zero-width or zero-height rectangles. -->
 </dl>
 
+<P>The element's ancestors may also have clipping regions (in case
+their <span class="propinst-overflow">'overflow'</span> property is
+not 'visible'); what is rendered is the intersection of the various
+clipping regions.
+
 <P>If the clipping region exceeds the bounds of the UA's
 document window, content may be clipped to that window by the
 native operating environment.
@@ -243,7 +259,8 @@ meanings:</p>
 <dt><strong>visible</strong>
 <dd>The generated box is visible. 
 <dt><strong>hidden</strong>
-<dd>The generated box is invisible, but still affects layout.
+<dd>The generated box is invisible (fully transparent), but still
+affects layout.
 <dt><strong>collapse</strong>
 <dd>Please consult the section on 
 <a href="tables.html#dynamic-effects">dynamic row and column
@@ -254,12 +271,13 @@ effects</a> in tables. If used on elements other than rows or columns,
 <P>This property may be used in conjunction with scripts to create
 dynamic effects.
 
-<div class="html-example"><P>
-In the following example, pressing either form button invokes a
-user-defined script function that causes the corresponding box to
-become visible and the other to be hidden. Since these boxes
-have the same size and position, the
-effect is that one replaces the other.
+<div class="html-example"><P> In the following example, pressing
+either form button invokes a user-defined script function that causes
+the corresponding box to become visible and the other to be
+hidden. Since these boxes have the same size and position, the effect
+is that one replaces the other. (The script code is in a hypothetical
+script language. It may or may not have any effect in a CSS-capable
+UA.)
 
 <pre>
 &lt;!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN"&gt;
@@ -307,11 +325,21 @@ effect is that one replaces the other.
 &lt;/HTML&gt;
 </pre>
 
-<P>Note that the <span class="propinst-position">'position'</span>
-property of each DIV element has the value 'relative'. A more
-visually appealing version of the above might be designed using
-overlapping <a href="visuren.html#absolute-positioning">
-absolutely positioned</a> boxes.</p>
 </div>
 </body>
 </html>
+<!-- Keep this comment at the end of the file
+Local variables:
+mode: sgml
+sgml-omittag:nil
+sgml-shorttag:nil
+sgml-minimize-attributes:nil
+sgml-always-quote-attributes:t
+sgml-indent-step:nil
+sgml-indent-data:t
+sgml-parent-document:nil
+sgml-exposed-tags:nil
+sgml-local-catalogs:nil
+sgml-local-ecat-files:nil
+End:
+-->