18344 2012-07-20 15:14:06 +0000 Appendix E imprecise about background propagation to canvas 2012-12-04 00:53:24 +0000 1 1 1 Unclassified CSS CSS Level 2 unspecified All Windows 3.1 NEW P2 normal --- 1 antonsforums bert public-css-bugzilla oldest_to_newest 71256 0 antonsforums 2012-07-20 15:14:06 +0000 E.2 says: # The canvas is transparent if contained within another, and given a # UA-defined color if it is not. It is infinite in extent and # contains the root element. Initially, the viewport is anchored with # its top left corner at the canvas origin. # # The painting order for the descendants of an element generating a # stacking context (see the 'z-index' property) is: # # 1. If the element is a root element: # 1. background color of element over the entire canvas. # 2. background image of element, over the entire canvas, anchored # at the origin that would be used if it was painted for the # root element. and E.3 (Notes) says: # The background of the root element is only painted once, over the # whole canvas. This fails to account for the special situation for the HTML BODY element described in 14.2: # The background of the root element becomes the background of the # canvas and covers the entire canvas, anchored (for # 'background-position') at the same point as it would be if it was # painted only for the root element itself. The root element does not # paint this background again. # # For HTML documents, however, we recommend that authors specify the # background for the BODY element rather than the HTML element. # For documents whose root element is an HTML "HTML" element or # an XHTML "html" element that has computed values of 'transparent' # for 'background-color' and 'none' for 'background-image', user # agents must instead use the computed value of the background # properties from that element's first HTML "BODY" element or XHTML # "body" element child when painting backgrounds for the canvas, and # must not paint a background for that child element. Such # backgrounds must also be anchored at the same point as they would # be if they were painted only for the root element. E.2 should acknowledge 14.2 somehow. 71257 1 antonsforums 2012-07-20 15:17:26 +0000 Reported by Anton Prowse Conversation begins: Bug description: http://lists.w3.org/Archives/Public/www-style/2012Jul/0478.html 71258 2 antonsforums 2012-07-20 15:18:36 +0000 Proposal A: In E.2, prepend the following existing prose: # The painting order for the descendants of an element generating a # stacking context (see the 'z-index' property) is: # # 1. If the element is a root element: # 1. background color of element over the entire canvas. # 2. background image of element, over the entire canvas, anchored # at the origin that would be used if it was painted for the # root element. with: | The background color and image of a child element of a root | element is sometimes painted over the entire canvas instead of that | of the root element itself. This happens _in some situations with | HTML and XHTML documents_<link to 14.2>. When this happens, no | background is painted for that child element. User agents must | apply these rules instead of the ones below whenever the | latter concern the elements and backgrounds in question. In E.3 (Notes), delete: # The background of the root element is only painted once, over the # whole canvas. Note: the editorial device used in this proposal (that of explicitly discussing background propagation prior to the painting order algorithm whilst leaving the algorithm written in a manner which focuses the more typical general case) is deliberate, since it aids the proposal for Bug 17782. Proposal: http://lists.w3.org/Archives/Public/www-style/2012Jul/0478.html