Text Styles

The text-align key is used to align text horizontally within the text box. It has the same function as the text-align property in CSS. The text can be aligned using the following keywords:

The text-align key is distinct from the similarly-named align key. The align key aligns a block element horizontally within its container.

The text-decoration key specifies the type of decoration, such as an underline, that is applied to the text. It accepts the following keywords:

When a key category allows the text-decoration key to be set, you can usually specify a text-decoration-color and text-decoration-width, too.

The font-size key specifies the size of the font. The font size may be specified either as a fixed value (e.g., 12) or a relative value (e.g., 0.8em). Font sizes are most often specified as a fixed value, though there are important cases when a relative value is more suitable. The font size always resolves to a point value when text is written to the PDF.

If the font size is specified as a number, or a number with a fixed unit of measurement (e.g., px), that value is converted to points. The conversion to points is done when the theme is loaded. The font-size key on the base category, as well as min, large, and small font size keys, must always be specified as a fixed value.

The only time this value is not used as specified is when the element is inside a table. If the font size on the table or AsciiDoc table cell differs from the base font size, all nested content is scaled by that ratio.

If the font size has relative units, em, %, or rem, then the value will be computed at the point of use.

For example, if the font size is 0.75em and the current font size is 12, then the font size will be 9.

Relative font sizes are best suited for inline elements, such as a codespan. Only use a relative font size when the font size should always be scaled relative to either the parent element (em or %) or base font size (rem).

The line-height key specifies the height of the box in which a single line of text is positioned. This theme key is used to control the spacing between wrapped lines.

The line height value is a multiplier of the font size. A line height value of 1 means that the height of the line should be equivalent to the height of the font. In this case, a wrapped line will start directly below the previous line, with no extra vertical space. A line height value of 2 means that the height of the line should be equivalent to twice the height of the font. In this case, there will be extra space between wrapped lines than what the text occupies. If the value is greater than 1, the text is positioned equidistant between the top and bottom of the line’s box.

The impact of the line height and how it’s computed is more complex than it would seem at first glance. Even if you set the value to 1, you may notice extra space between wrapped lines. As you’re no doubt aware, not all characters have the same height (e.g., x vs X). Furthermore, some characters have vertical strokes that rise above the lowercase letter x (ascenders) and some have strokes that drop below the lowercase letter x (descenders). We refer to the height of the lowercase letter x the x-height. The x-height is always less than—​and can vary considerably from—​the effective height of the font.

You can study the built-in line height by setting the base-line-height key to 1, the mark-border-offset key to 0, then applying the mark formatting to various characters, words, and phrases.

The background color under the marked text stretches across the entire built-in line height. This reveals the difference between the height of the text and the height of the line. If you increase the line height value, you’ll see spacing appear between the background color stripes of wrapped lines.

The reserved height for ascenders and descenders, which can differ, also impacts how the text is positioned vertically within the line height. The text is positioned so that the space above and ascender and the space below a descender are equivalent. If the text has no ascenders or descenders (e.g., x), it can appear slightly higher or lower in the line than expected. It all depends on the properties of the font. You can observe this behavior by testing the previous example with different fonts. Try change the font family (e.g., Helvetica or Times-Roman) to see what impact it has.

When you’re choosing a line height value, study the interplay between characters with ascenders (e.g, h) and descenders (e.g., y). Use marked text to reveal the space occupied by a single line. Adjust the line height value until the spacing between the lines matches what you expect.

The font-style key specifies the font variant in a font family that the text should use. The key accepts the following keywords:

Usually, you can specify a font style wherever you can set a font family (font-family). The converter uses the values of both keys in combination to locate the correct font within a font stack.

The text-transform key changes the case of the text. It accepts the following keywords:

The text-transform key can’t be set on the base category.

For inline elements that support a border or background color, the decoration is fit to the text by default. That means it stretches from the start of the first character to the end of the last character horizontally and across the entire built-in line height of the text vertically. The line-height key on the block element (e.g., paragraph) does not affect the decoration.

To extend the decoration out evenly on both axes, set the border-offset key to a positive number. This setting does not affect the layout of the text. It only swells the extent of the decoration under it.