Limitations

htmlbag deliberately does not implement parts of HTML/CSS that would require fundamentally different layout machinery. This page lists what’s missing and where the line is.

Side floats

CSS float: left | right places a float beside the text, which wraps around it. It does not do everything a browser does yet (htmlbag#16):

• A float without a width shrinks to its longest line. One that holds a block image, a rule, or a table inside a border is set at the full measure instead, and the text after it goes below it.
• A float floats as a child of a block container and at the start of a paragraph, as in <p><img style="float: left"> text</p>. One later in the paragraph, such as <p>text <img style="float: left"> more text</p>, inside a link, in a list item, or in a paragraph with a border or padding of its own is set inline.
• A float at the start of a paragraph stands at the edge of the paragraph’s container, so a side margin of the paragraph is outside it.
• A float that leaves the text no room beside the floats already there goes below the one that ends first, as in a browser, but the text after it goes below with it instead of staying beside the floats above.
• Where a negative margin lets text run over a float, the float covers the text; a browser paints the text on top. A negative margin-top does not raise a float.
• A float is not split across pages. One that does not fit moves to the next page with the text beside it; one taller than a whole page runs past the bottom of the page it starts on.

Multi-column layout

CSS column-count is supported, with column-gap, column-span, column-fill and column-rule (see CSS properties). It has these limits:

• Columns are laid out on body, or on a direct child of body without a border, a background or padding, whose siblings then span the columns. On any other element the content is set in one column, with a warning.
• column-width is not read; columns takes only the count.
• solid is the only column-rule-style that is drawn.
• Floats and footnotes inside an element with column-span: all are placed at the foot of the page, and the columns below do not make room for them.
• With column-fill: balance, a row whose content starts in its last column stays full.

Running headers and footers from body content

CSS running() / element() (GCPM) are supported: an element with position: running(name) is captured out of the flow and a page margin box places it with content: element(name). See CSS support. The related string-set property (copying just a text string instead of an element) is not implemented; use a running element instead.

Page master alternation

The pseudo-class page selectors @page :first, :right and :left are supported: size, margin / margin-{top,right,bottom,left}, background-color and background-image resolve per page and cascade over the generic @page rule. See CSS support. @page :blank is not implemented.

When a later page’s @page rule gives a different content width (a different left or right margin), running text, a paragraph that runs over the page break and a table are set again at the new width. A few things keep the width of the page they started on: a block with a border or background that runs over the page break, a paragraph or block inside another block that runs over it, the rest of a table row split at the break, and absolutely positioned blocks.

Static-typing-mode XPath

Internal — only relevant if you embed htmlbag’s XPath usage. The underlying goxpath engine implements XPath 1.0 / 2.0 basic semantics; XPath 2.0 strict static-typing mode (XPST0005 errors for empty-by-construction expressions) is not enforced.

What this means in practice

A document with figures, tables, lists, footnotes, top and bottom floats, side floats, running headers and footers, and different :first, :left and :right pages is covered, in one column or in columns across the body. Columns inside a box of their own are not.