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--- topics:overflow-formatting-context [2012/05/17 11:20] – [Data entry] fantasai
+++ topics:overflow-formatting-context [2012/05/22 00:02] – aprowse
@@ Line 14: / Line 14: @@
 === Problem Statement ===
-The ''overflow'' property says it only applies to block containers, but it should also apply to tables and flex containers
+The ''overflow'' property says it only applies to block containers, but it should also apply to tables and flex containers.
-=== Proposal ===
+=== Related Problems ===
-In 11.1.1 (Overflow), replace:
+For non-root elements whose position is 'relative' or 'static', the containing block is defined to be formed by the content edge of the nearest block container ancestor box [or table box], but it should be formed by other types of layout container for certain elements in other layout schemes (for example by the flexbox for flexbox items).
-   # Applies to: block containers
+Note that the issue of other layout schemes needing such adjustments to ''overflow'' and the containing block hierarchy already exists within CSS21 itself:
+  * Bug 15381 - Incorrect "Applies To" line for 'overflow' property (Error in resolution for Issue 120) - https://www.w3.org/Bugs/Public/show_bug.cgi?id=15381
+  * Bug 15686 - Containing block for internal tables elements should be table not table wrapper (Error in resolution for Issue 120) - https://www.w3.org/Bugs/Public/show_bug.cgi?id=15686
+Both these issues arose through an oversight when introducing the terms "block container" etc, namely that table boxes were overlooked.  This illustrates the special-casing that spec editors must remember to perform in individual layout specs if the problem is not solved more generally.
-with:
+=== Approach ===
-   | Applies to: block containers and boxes that establish a formatting context
+  * Define the concept of a "formatting context".  (Alternative possibility: redefine "block formatting context" to not only apply to blocks.  See Bug 17121 - Desire to introduce the concept of a "formatting context" for forwards compatibility - https://www.w3.org/Bugs/Public/show_bug.cgi?id=17121 )
+  * Change the definition of ''overflow''
+  * Change the containing block hierarchy (optional addition to proposal)
+=== Proposal ===
+== Formatting context ==
 In 9.4 (Normal flow), replace:
@@ Line 64: / Line 73: @@
    | table box. These boxes have content and borders, and cells have
    | padding as well. Internal table elements do not have margins.
+== ''overflow'' ==
+In 11.1.1 (Overflow), replace:
+   # Applies to: block containers
+with:
+   | Applies to: block containers and boxes that establish a formatting context
+== Containing block hierarchy (optional addition to proposal) ==
+(This has neither been reviewed nor discussed on the public mailing list.)
+In 10.1 (Definition of "containing block"), replace:
+   # 2. For other elements, if the element's position is 'relative' or
+   #    'static', the containing block is formed by the content edge of
+   #    the nearest block container ancestor box.
+with:
+   | 2. For other elements, if the element's position is 'relative' or
+   |    'static', the containing block is formed by the content edge of
+   |    the nearest ancestor box that is a block container or which
+   |    establishes a formatting context.
 === Links to More Info ===
   - Thread start: http://lists.w3.org/Archives/Public/www-style/2012May/0438.html
+  - Bug 17122 - "Applies To" line for 'overflow' property hinders forwards-compatibility - https://www.w3.org/Bugs/Public/show_bug.cgi?id=17122