TextStyle Class

The background is painted by DrawingCanvas.FillText before the text of the whole layout. On each line, it is one rectangle as wide as the advances of the text of the style, the white space between its words included (not the white space that hangs at the end of a wrapped line), and as tall as the primary font of the style: from its ascent to its descent, whatever the height of the line. It is not part of the outlines of the text: DrawingCanvas.StrokeText and TextLayout.ToPath leave it out.

The text of each span of the style is one unit of its line: it is shaped as a horizontal line of one font (the first font of the stack that has all its characters), centered across the line and on the middle of one em down the line, and it advances by one em. Text that is wider than one em takes the forms its font has for half, a third or a quarter of an em when it is two, three or four characters long (hwid, twid, qwid), and is narrowed to one em if it is still too wide. A line never ends inside it, and the letter spacing, the word spacing and justification do not change it. Its decorations are those of upright text.

It is the all value of the text-combine-upright property of CSS; TextLayoutOptions.CombineUprightDigits combines the short numbers of a text. It changes nothing in a horizontal layout, nor in one whose orientation is TextOrientation.Sideways.

A font can draw the same characters differently for different languages: the Cyrillic letters of Serbian and of Bulgarian, the ideographs of Chinese, Japanese and Korean, the letters around the dotless i of Turkish. It does so with a language system of its OpenType Layout tables for each of these languages. The language of the style selects the language system of each font: the first one the font has among the tags the registry of OpenType gives for the language, or else its default language system, as without a language.

The tag is not checked against the registry of language subtags, and the casing of its subtags does not matter. The language is found from the language subtag, and from the script, region and variant subtags where they select a written form: zh-Hans, zh-Hant, zh-HK, el-polyton, und-fonipa. A language the registry of OpenType has no tag for changes nothing.

With a stack that falls back to the installed fonts (FontStack.WithInstalledFallback), the language also chooses the families its Han ideographs are looked for in: those of Japanese (ja), Korean (ko), Traditional Chinese (zh-Hant, zh-TW), the Chinese of Hong Kong (zh-HK, yue) or Simplified Chinese (zh, zh-Hans, and a text without a language or in another language). The fonts of the stack itself are used in their order, whatever the language. The language changes nothing else: not where lines break.

The space is added after each cluster: a character with its marks, a ligature. Ligatures the font forms by default are still formed; turn the feature liga off to space their letters.

The stroke is drawn by DrawingCanvas.FillText after the text of the whole layout is filled, over it. A centered pen covers the edge of the glyphs by half its width; with PenAlignment.Outside, the stroke is around the glyphs and leaves them as they are filled. The glyphs of one pen are stroked as one shape; the decorations, the glyphs a font draws with its own colors and what a synthetic bold adds to a glyph are not stroked. The width of the pen is in pixels, whatever the size of the text.

FontSynthesis.Oblique slants every outline to the right, around the baseline; the marks of a letter follow it, the advances do not change and the decorations stay straight.

FontSynthesis.Bold thickens the glyphs of a filled text: each glyph is filled together with a stroke of its outline, 1/24 of the size wide, whose corners are kept sharp unless they are sharper than 60 degrees. Each glyph that takes room takes 1/24 of the size more and is drawn in the middle of it. A stroked text (StrokeText) and the path of a layout (TextLayout.ToPath) have the outlines of the font, which the bold does not change.

The glyphs a font draws with its own colors, such as emoji, are drawn as they are.