3. Page layout

The page-break command .bp ends the current HTML page and start a new one. .bp causes a page-break in both the HTML and the print outputs.

Generally, page-breaks require a different aesthetic in HTML than in print. You can use troff conditionals to express this difference:

    .if \n[.troff2page] .bp

causes a page-break only in the HTML, whereas

    .if !\n[.troff2page] .bp

causes a page-break only in print.

As can be seen, the number register \n[.troff2page] has a true value, i.e., a number greater than zero, only when troff2page processes the document.2

If may be convenient to define a .HBP macro that causes a page-break only for HTML:

    .de HBP
    .if \n[.troff2page] .bp
    ..

Note that troff2page, like troff, does not automatically cause a page break at the sectioning commands. Use .bp or a macro like .HBP to explicitly to insert breaks as needed.

Each page in a multiple-page HTML output has a navigation bar at its head and foot. The bar contains links to the first, previous, and next page, and the table-of-contents and index pages. If any of these pages doesn’t exist, or if it is the same as the page containing the navigation bar, then the link for it is disabled.

HTML-style paragraphs

By default, troff2page sets paragraphs exactly as groff does: the first lines of paragraphs are indented (unless explicitly disabled via an .LP), and the vertical distance between adjacent paragraphs is the same smallish amount that groff employs. These two values are given by the number registers PI and PD, which (for the ms format) are 0.3n and 0.3v respectively.

If you wish to have the kind of block paragraphs customary in HTML, it is not enough to set PI to 0, for the prevailing value of PD is too small to comfortably tell adjacent paragraphs apart. You could set PD to a larger value, but as a convenience, troff2page allows you to set PD to a negative value, which leads to whatever default paragraph separation that HTML uses. Note that setting PD to a negative value should be done only for HTML, as groff will happily overstrike text in order to respect a negative PD:

    .if \n[.troff2page] \{\
    .nr PI 0n
    .nr PD 0-1p
    .\}

Unlike groff ms, which uses the line length given by the register LL, troff2page by default does not restrict the width of its HTML pages. Text will narrow or widen to fit the current browser window width. However, if you explicitly set LL (instead of relying on ms’s default), troff2page will respect that line length. Nevertheless, if the user shrinks the browser window to a width less than LL, the text will correspondingly shrink too to fit the window. This is to avoid the need for horizontal scrolling.

A good LL value for troff2page should be a bit larger than ms’s 6 inches, which is too narrow for a browser. The following sets it to 18 cm, making sure it takes effect only for HTML:

    .if \n[.troff2page] .nr LL 18c


2 The greater-than-zero number held in the register \n[.troff2page] is in fact the version number of the troff2page program processing the document. This is a number such as 20050327, which would be the version number of the troff2page released on 2005 March 27. \n[.troff2page] could plausibly be used to distinguish not just troff2page from troff, but also between various versions of troff2page. Thus, one could, if the need were dire, write a document that translates differently with different versions of troff2page.