aka “The Recommendation Strikes Back” I came across a very interesting section of the XSL-FO 1.1 Recommendation. This is the description of the from-page-master-region function in section 5.10.4, “Property Value Functions”. This function can be used to determine the computed value of the “writing-mode” and “reference-orientation” properties. To keep it simple I’ll leave “writing-mode” aside and assume that it’s always kept to its default value of “lr-tb”.
Preliminary note: fo:simple-page-master, fo:region-body, fo:region-before and the like /do not/ generate areas. They are simply /used/ to generate areas, the actual generation is done by fo:page-sequence. fo:simple-page-master is used to generate a page-viewport-area/ page-reference-area pair. The reference-orientation of the page-viewport-area is set to 0. Now there is, at best, an ambiguity in the description of Section 6.4.13, “fo:simple-page-master”: • first there is a note saying “For example, if the writing-mode of the fo:simple-page-master is ‘lr-tb’, then these regions correspond to the body of a document, the header, the footer, the left sidebar, and the right sidebar.” • then there is this sentence: “The ‘writing-mode’ of the page is used to determine the placement of the five regions on the master.” That seems to indicate that the value of the “writing-mode” property set on the fo:simple-page-master is used to determine the placement of the regions. • but further below there is this: “The reference-orientation of the page-reference-area and writing-mode of the page-viewport-area are determined by the formatting object that generates the area (see 6.4.5 fo:page-sequence).” In Section 6.4.15, “fo:region-before”, there is this: “This region specifies a viewport/reference pair that is located on the ‘before’ side of the page-reference-area.” So, if the fo:simple-page-master has a “reference-orientation” of 0 and the fo:page-sequence a “reference-orientation” of 90, who wins? Let’s assume that the first 2 bullet points above are only vague descriptions and that the 3rd point is normative. If we want to use the values specified on the respective regions instead, then we can use the from-page-master-region function for the value of the “reference-orientation” or “writing-mode” properties set on fo:page-sequence, as clearly described in Section 5.10.4. Now, let’s take the following XSL-FO document: <?xml version="1.0" standalone="no"?> <fo:root xmlns:fo="http://www.w3.org/1999/xsl/format";> <fo:layout-master-set> <fo:simple-page-master master-name="page" page-width="21cm" page-height="29.7cm" reference-orientation="90"> <fo:region-body margin-top="15pt" reference-orientation="90"/> <fo:region-before extent="10pt"/> </fo:simple-page-master> </fo:layout-master-set> <fo:page-sequence master-reference="page" reference-orientation="from-page-master-region()"> <fo:static-content flow-name="xsl-region-before" font-size="8pt"> <fo:block>xsl-region-before</fo:block> </fo:static-content> <fo:flow flow-name="xsl-region-body"> <fo:block>lorem ipsum dolor sit amet, consectetur adipiscing elit. vestibulum arcu felis, gravida vitae laoreet in, molestie nec libero. mauris non enim diam. pellentesque nisl diam, aliquet nec euismod vitae, convallis nec massa. mauris gravida arcu ac erat euismod molestie. maecenas eget neque in sem aliquam viverra. vivamus dictum lobortis scelerisque.</fo:block> </fo:flow> </fo:page-sequence> </fo:root> Because the from-page-master-region function is used, the “reference-orientation” property specified on the fo:simple-page-master and the regions is used to determine their orientations. So the content-rectangle of the page-reference-area is like this: ___________________________ | end | | | | | | | | | | | |before |after | | | | | | | | | | | | |_________________________| start While the content-rectangle of the region-viewport-area for the region-before is supposed to be like this: after ____ | | | | | | | | | | end| |start | | | | | | | | | | |__| before which is completely inconsistent with the description of fo:region-before: “The before-edge of the content-rectangle of this region-viewport-area is positioned coincident with the before-edge of the content-rectangle of the page-reference-area generated using the parent fo:simple-page-master. The block-progression-dimension of the region-viewport-area is determined by the extent trait on the fo:region-before formatting object.” The inconsistency can be resolved by replacing content-rectangle with border-rectangle in the excerpt above. Because, as explained in Section 4.2.3, “Geometric Definitions”, the definition of the before/after/start/end-edges of the content-rectangle of an area uses the inline/block-progression-direction of that area; Whereas the border/padding/allocation-rectangles use the directions of the parent area. Unless, of course, I have completely missed the point, which might well be the case. As a side note, FOP does not follow the Recommendation regarding the implementation of the “reference-orientation” property on fo:page-sequence. It behaves as if that property was set to “from-page-master-region()”, whereas it doesn’t even implement that function. Why am I raising this topic? Take an XSL-FO document, add a bit of overflow=“hidden” here and there, a pinch of reference-orientation, introduce IPD, BPD, clipping rectangles and transformation matrices, shake well... and you obtain food for thought regarding Bugzilla #49910. https://issues.apache.org/bugzilla/show_bug.cgi?id=49910 Any thoughts? Vincent
