By "extension", we mean any data that can be placed in the input XML document that is not addressed by the XSL-FO standard. By having a mechanism for supporting extensions, Apache™ FOP is able to add features that are not covered in the specification.
The extensions documented here are included with FOP, and are automatically available to you. If you wish to add an extension of your own to FOP, please see the Developers' Extension Page.
Please see the SVG documentation for more details.
By convention, FO extensions in FOP use the "fox" namespace prefix.
To use any of the FO extensions, add a namespace entry for
http://xmlgraphics.apache.org/fop/extensions to the root element:
In old versions of Apache FOP there was a fox:outline element
which was used to create outlines in PDF files. The redesigned code makes use
of the bookmark feature defined in the W3C XSL 1.1 standard.
Use the fox:destination element to define "named destinations" inside a PDF document. These are useful as fragment identifiers, e.g. "http://server/document.pdf#anchor-name". fox:destination elements can be placed almost anywhere in the fo document, including a child of root, a block-level element, or an inline-level element. For the destination to actually work, it must correspond to an "id" attribute on some fo element within the document. In other words, the "id" attribute actually creates the "view" within the PDF document. The fox:destination simply gives that view an independent name.
This extension element hasn't been reimplemented for the redesigned code, yet.
The two proprietary extension properties, fox:orphan-content-limit and fox:widow-content-limit, are used to improve the layout of list-blocks and tables. If you have a table with many entries, you don't want a single row to be left over on a page. You will want to make sure that at least two or three lines are kept together. The properties take an absolute length which specifies the area at the beginning (fox:widow-content-limit) or at the end (fox:orphan-content-limit) of a table or list-block. The properties are inherited and only have an effect on fo:table and fo:list-block. An example: fox:widow-content-limit="3 * 1.2em" would make sure the you'll have at least three lines (assuming line-height="1.2") together on a table or list-block.
This is a proprietary extension element which allows to add whole images as pages to
an FO document. For example, if you have a scanned document or a fax as multi-page TIFF
file, you can append or insert this document using the fox:external-document
element. Each page of the external document will create one full page in the target
format.
The fox:external-document element is structurally a peer to
fo:page-sequence, so wherever you can put an fo:page-sequence
you could also place a fox:external-document.
Therefore, the specified contents for fo:root change to:
(layout-master-set, declarations?, bookmark-tree?, (page-sequence|page-sequence-wrapper|fox:external-document|fox:destination)+)
The fox:external-document extension formatting object is used to specify
how to create a (sub-)sequence of pages within a document. The content of these pages
comes from the individual subimages/pages of an image or paged document (for example:
multi-page TIFF in the form of faxes or scanned documents, or PDF files). The
formatting object creates the necessary areas to display one image per page.
In terms of page numbers, the behaviour is the same as for
fo:page-sequence. The placement of the image inside the page is similar
to that of fo:external-graphic or fo:instream-foreign-object,
i.e. the viewport (and therefore the page size) is defined by either the intrinsic
size of the image or by the size properties that apply to this formatting object.
Content: EMPTY
The following properties apply to this formatting object:
Datatype "page-set": Value: auto | <integer-range>, Default: "auto" which means all pages/subimages of the document. <integer-range> allows values such as "7" or "1-3"
fox:external-document is not suitable for concatenating FO documents.
For this, XInclude is recommended.
For fo:block-container elements whose absolute-position set to
"absolute" or "fixed" you can use the extension attribute fox:transform
to apply a free-form transformation to the whole block-container. The content of the
fox:transform attribute is the same as for
SVG's transform attribute.
The transformation specified here is performed in addition to other implicit
transformations of the block-container (resulting from top, left and other properties)
and after them.
Examples: fox:transform="rotate(45)" would rotate the block-container
by 45 degrees clock-wise around its upper-left corner.
fox:transform="translate(10000,0)" would move the block-container to the
right by 10 points (=10000 millipoints, FOP uses millipoints internally!).
XSL-FO supports specifying color using the rgb(), rgb-icc() and system-color() functions. Apache FOP provides additional color functions for special use cases. Please note that using these functions compromises the interoperability of an FO document.
color cmyk(numeric, numeric, numeric, numeric)
This function will construct a color in device-specific CMYK color space. The numbers must be between 0.0 and 1.0. For output formats that don't support device-specific color space the CMYK value is converted to an sRGB value.
color rgb-icc(numeric, numeric, numeric, #CMYK, numeric, numeric, numeric, numeric)
The rgb-icc function will respond to a pseudo-profile called "#CMYK"
which indicates a device-specific CMYK color space. The "#CMYK" profile is implicitely
available and doesn't have to be (and cannot be) defined through an
fo:color-profile element. It is provided for compatibility with certain
commercial XSL-FO implementations. Please note that this is not part of the official
specification but rather a convention. The following two color specifications are
equivalent:
cmyk(0%,0%,20%,40%)rgb-icc(153, 153, 102, #CMYK, 0, 0, 0.2, 0.4)
This section defines a number of extensions related to
prepress support.
fox:scale defines a general scale factor for the generated pages.
fox:bleed defines the
bleed area for a page.
fox:crop-offset defines the outer edges of the area in which crop marks,
registration marks, color bars and page information are placed.
For details, please read on below.
Value: <number>{1,2}
Initial: 1
Applies to: fo:simple-page-master
This property specifies a scale factor along resp. the x and y axes. If only one number is provided it is used for both the x and y scales. A scale factor smaller than 1 shrinks the page. A scale factor greater than 1 enlarges the page.
Value: <length>{1,4}
Initial: 0pt
Applies to: fo:simple-page-master
If there is only one value, it applies to all sides. If there are two values, the top and bottom bleed widths are set to the first value and the right and left bleed widths are set to the second. If there are three values, the top is set to the first value, the left and right are set to the second, and the bottom is set to the third. If there are four values, they apply to the top, right, bottom, and left, respectively. (Corresponds to the definition of padding).
This extension indirectly defines the BleedBox and is calculated by expanding the TrimBox by the bleed widths. The lengths must be non-negative.
Value: <length>{1,4}
Initial: bleed (see below)
Applies to: fo:simple-page-master
Same behaviour as with fox:bleed. The initial value is set to the same values as the fox:bleed property.
This extension indirectly defines the MediaBox and is calculated by expanding the TrimBox by the crop offsets. The lengths must be non-negative.
Value: [trim-box | bleed-box | media-box]
Initial: media-box
Applies to: fo:simple-page-master
The crop box controls how Acrobat displays the page (CropBox in PDF) or how the Java2DRenderer sizes the output media. The PDF specification defines that the CropBox defaults to the MediaBox. This extension follows that definition. To simplify usage and cover most use cases, the three supported enumeration values "trim-box", "bleed-box" and "media-box" set the CropBox to one of those three other boxes.
If requested in the future, we could offer to specify the CropBox in absolute coordinates rather than just by referencing another box.