pango-0.12.2: Binding to the Pango text rendering engine.

Portabilityportable (depends on GHC)



Fonts. The selection of an appropriate font to render text becomes a substantial task in the presence of Unicode where a single font does not cover the whole range of possible characters. Pango provides several concepts to find appropriate fonts and to query information about them:

  • FontDescription: Font descriptions provide a way to query and state requirements on fonts. This data structure has several fields describing different characteristics of a font. Each of these fields can be set of left unspecified.
  • FontMap : A font map represents the set of fonts available for a particular rendering system. In particular this map defines the relation between font size and pixel size in terms of the output medium.
  • FontFamily : A font family represents a set of fonts that have related faces, that is, their faces share a common design, but differ in slant, weight, width and other aspects.
  • FontFace: A face is a specific font where all characteristics are fixed except for the size.
  • Font: A font in the underlying rendering system.
  • FontMetrics: Information about the font that will be used to render a specific Context or PangoItem.



data FontDescription Source

A possibly partial description of font(s).

fontDescriptionNew :: IO FontDescriptionSource

Create a new font description.

  • All field are unset.

fontDescriptionCopy :: FontDescription -> IO FontDescriptionSource

Make a deep copy of a font description.

fontDescriptionSetFamily :: FontDescription -> String -> IO ()Source

Set the font famliy.

  • A font family is a name designating the design of the font (e.g. Sans or Times) without the variant.
  • In some contexts a comma separated list of font families can be used.

fontDescriptionGetFamily :: FontDescription -> IO (Maybe String)Source

Get the font family.

  • Nothing is returned if the font family is not set.

fontDescriptionSetSize :: FontDescription -> Double -> IO ()Source

Set the size field.

  • The given size is in points (pts). One point is 1/72 inch.

data FontMask Source

Flags denoting which fields in a font description are set.


Bounded FontMask 
Enum FontMask

Set the style field.

Flags FontMask 

fontDescriptionUnsetFields :: FontDescription -> [FontMask] -> IO ()Source

Reset fields in a font description.

fontDescriptionMerge :: FontDescription -> FontDescription -> Bool -> IO ()Source

Merge two font descriptions.

  • Copy fields from the second description to the first. If the boolean parameter is set, existing fields in the first description will be replaced.

fontDescriptionBetterMatch :: FontDescription -> FontDescription -> FontDescription -> BoolSource

Determine which of two descriptions matches a given description better.

  • Returns True if the last description is a better match to the first arguement than the middle one.
  • Approximate matching is done on weight and style. If the other attributes do not match, the function returns False.

fontDescriptionFromString :: String -> IO FontDescriptionSource

Create a font description from a string.

  • The given argument must have the form [FAMILY-LIST] [STYLE-OPTIONS] [SIZE] where FAMILY_LIST is a comma separated list of font families optionally terminated by a comma, STYLE_OPTIONS is a whitespace separated list of words where each word describes one of style, variant, weight or stretch. SIZE is a decimal number giving the size of the font in points. If any of these fields is absent, the resulting FontDescription will have the corresponing fields unset.

fontDescriptionToString :: FontDescription -> IO StringSource

Convert a font description to a string.

pangoFontMapListFamilies :: FontMap -> IO [FontFamily]Source

Ask for the different font families that a particular back-end supports.

  • The FontMap can be acquired by calling Graphics.Rendering.Pango.Cairo.cairoFontMapGetDefault.

pangoFontFamilyIsMonospace :: FontFamily -> BoolSource

Ask if the given family contains monospace fonts.

  • A monospace font is a font designed for text display where the characters form a regular grid. For Western languages this would mean that the advance width of all characters are the same, but this categorization also includes Asian fonts which include double-width characters: characters that occupy two grid cells.
  • The best way to find out the grid-cell size is to query the members of the according FontMetrics structure.

pangoFontFamilyListFaces :: FontFamily -> IO [FontFace]Source

Ask for the faces contained in a particular family.

  • Asks for all font faces in the given family. The faces in a family share a common design, but differ in slant, weight, width and other aspects. For example, the font family Sans contains several fonts such as Helvetica and Arial.

pangoFontFaceListSizes :: FontFace -> IO (Maybe [Double])Source

Ask for available sizes of this font face.

  • List the available sizes for a font. This is only applicable to bitmap fonts since all other fonts can be scaled arbitrarily. For scalable fonts, this function returns Nothing. The sizes returned are in ascending order, their unit is points (1/72 inch).

pangoFontFaceDescribe :: FontFace -> IO FontDescriptionSource

Ask for a description of this face.

  • Returns the family, style, variant, weight and stretch of a FontFace. The size field of the resulting font description will be unset.

class GObjectClass o => FontClass o Source