revising pseudo-algorithm; revising text on paint order; revising description on clipping of floats

Author: howcome

css-multicol/Overview.src.html

@@ -767,23 +767,11 @@ <h3>'columns'</h3>
 <h3>Pseudo-algorithm</h3>
 
 <P>The pseudo-algorithm below determines the used values for
-'column-count' (N) and 'column-width' (W). There are two other
-variables in the pseudo-algorithm:
-
-<ul>
-
-<li><code>available-width</code>: if the used width of the
-multi-column element has not been determined when the 'column-count'
-and 'column-width' must be determined (e.g., if it is floating with a
-'width' of 'auto' as per CSS 2.1 section 10.3.5) this variable is
-<code>unknown</code>, otherwise it is the same as the used width of
-the multi-column element. In vertical text, the used height replaces used width in this calculation.
-
-<li><code>shrink-to-fit</code>: this variable represents the result of
-a <em>shrink-to-fit</em> computation. CSS does not define the exact
-algorithm. 
+'column-count' (N) and 'column-width' (W). There is one other variable
+in the pseudo-algorithm: U is the used width of the multi-column
+element.
 
-</ul>
+<p class=note>The used width U of the multi-column element can depend on the element's contents, in which case it also depends on the computed values of the 'column-count' and 'column-width' properties. This specification does not define how U is calculated. Another module (probably the Basic Box Model [[CSS3BOX]] or the Intrinsic & Extrinsic Sizing Module [[CSS3-SIZING]]) is expected to define this.
 
 <p>Two assumptions are being made by the pseudo-algorithm:
 
@@ -792,52 +780,14 @@ <h3>Pseudo-algorithm</h3>
 <li>that no column breaks are added through style sheets
 </ul>
 
-<p>The <code>floor()</code> function rounds a number to the next smaller integer.
+<p>The <code>floor(X)</code> function returns the largest integer Y ≤ X.
 
-<!--
-<pre>
-(01)  if ((column-width = auto) and (column-count = auto)) or
-(02)     ((available-width = unknown) and (column-count = auto)) then
-(03)    exit; /* no columns */
-(04)  fi
-(05)  
-(06)  if (available-width = unknown) and (column-count != auto) and (column-width != auto) then
-(07)    N := column-count;  
-(08)    W := column-width;
-(09)    exit;
-(10)  fi
-(11)  
-(12)  if (available-width = unknown) then
-(13)    available-width := shrink-to-fit;
-(14)  fi
-(15)  
-(16)  if (column-width = auto) then
-(18)    N := column-count;
-(19)    W := max(0, (available-width - ((N - 1) * column-gap))/N);
-(27)  elsif (column-count = auto) then
-(28)    if (column-width >= available-width) then
-(29)      N := 1
-(30)      W := available-width;
-(31)    else
-(32)      N := floor((available-width + column-gap) / (column-width + column-gap));
-(33)      W := ((available-width + column-gap) / N) - column-gap;
-(34)    fi
-(35)  elsif (column-width >= available-width) then
-(36)    N := 1
-(37)    W := available-width;
-(38)  else
-(39)    N := min(column-count, floor((available-width + column-gap) / (column-width + column-gap)))
-(40)    W := ((available-width + column-gap) / N) - column-gap;
-(41)  fi
-</pre>
-
-<p><span class=issue>Alternative encoding of pseudo-algorithm:
--->
 
 <pre>
 (01)  if ((column-width = auto) and (column-count = auto)) then
 (02)        exit; /* not a multicol element */
 
+<!--
 (03)  if ((available-width = unknown) and (column-count = auto)) then
 (04)    exit; /* no columns */
 
@@ -848,22 +798,23 @@ <h3>Pseudo-algorithm</h3>
 
 (09)  if (available-width = unknown) then
 (10)    available-width := shrink-to-fit;
+-->
 
-(11)  if (column-width = auto) and (column-count != auto) then
-(12)    N := column-count;
-(13)    W := max(0, (available-width - ((N - 1) * column-gap)) / N);
-(14)  exit;
-
-(15)  if (column-width != auto) and (column-count = auto) then
-(16)    N := max(1, floor((available-width + column-gap) / (column-width + column-gap)));
-(17)    W := ((available-width + column-gap) / N) - column-gap;
-(18)  exit;
-
-(19)  if (column-width != auto) and (column-count != auto) then
-(20)    N := min(column-count, floor((available-width + column-gap) / (column-width + column-gap)))
-(21)    N := max(1, N); 
-(22)    W := ((available-width + column-gap) / N) - column-gap;
-(23)  exit
+(03)  if (column-width = auto) and (column-count != auto) then
+(04)    N := column-count;
+(05)    W := max(0, (U - ((N - 1) * column-gap)) / N);
+(06)  exit;
+
+(07)  if (column-width != auto) and (column-count = auto) then
+(08)    N := max(1, floor((U + column-gap) / (column-width + column-gap)));
+(09)    W := ((U + column-gap) / N) - column-gap;
+(10)  exit;
+
+(11)  if (column-width != auto) and (column-count != auto) then
+(12)    N := min(column-count, floor((U + column-gap) / (column-width + column-gap)))
+(13)    N := max(1, N); 
+(14)    W := ((U + column-gap) / N) - column-gap;
+(15)  exit
 </pre>
 
 
@@ -874,7 +825,7 @@ <h3>Pseudo-algorithm</h3>
 'column-count' affect the layout. If 'column-width' has a value other
 than ''auto'', 'column-count' indicates the maximum number of columns.
 However, both 'column-width' and 'column-count' are honored when the
-width of the element has not been determined. This can, e.g., be the
+width of the element depends on its contents. This can, e.g., be the
 case for table cells and floats.
 
 
@@ -900,9 +851,9 @@ <h2>Column gaps and rules</h2>
 column rule will not alter the placement of anything else. If a column
 rule is wider than its gap, the adjacent column boxes will overlap the
 rule, and the rule may possibly extend outside the box of the multicol
-element. Column rules are painted just above the background of the
-multicol element. Column rules are only drawn between two columns that
-both have content.
+element. Column rules are painted in the inline content layer, but
+below all inline content inside the multicol element. Column rules are
+only drawn between two columns that both have content.
 
 <h3>'column-gap'</h3>
 
@@ -1627,13 +1578,12 @@ <h2>Filling columns</h2>
 
 <p>There are two strategies for filling columns: columns can either be
 balanced, or not. If columns are balanced, user agents should try to
-fill all columns in a row so that the columns appear to have the same
-amount of content, while also trying to minimize the overflow content.
-If columns are not balanced, they are filled sequentially; some
-columns may end up partially filled, or with no content at all. In any
-case, user agents must honor forced page breaks and should try to
-honor 'widows', 'orphans' and other properties that may affect column
-lengths.
+minimize the variation in content between columns, while also trying to
+minimize the overflow content. If columns are not balanced, they are
+filled sequentially; some columns may end up partially filled, or with
+no content at all. In any case, user agents must honor forced page
+breaks and should try to honor 'widows', 'orphans' and other
+properties that may affect column lengths.
 
 <h3 id='cf'>'column-fill'</h3>
 
@@ -1694,7 +1644,7 @@ <h2>Overflow</h2>
 
 <h3>Overflow inside multicol elements</h3>
 
-<p>Content in the normal flow that extends into column gaps (e.g.,
+<p>Floated or in-flow content that extends into column gaps (e.g.,
 long words or images) is clipped in the middle of the column gap.
 
 <div class=example>
@@ -2091,7 +2041,7 @@ <h2 class=no-num id=acknowledgments>Acknowledgments</h2>
 <p>This document is based on several older proposals and comments on
 older proposals. Contributors include 
 
-Øyvind Stenhaug, 
+Øyvind Stenhaug, 
 Sylvain Galineau, 
 Giovanni Campagna, 
 David Hyatt,