Graphics.Rendering.Pango.Font

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.

Documentation

data FontDescription

A possibly partial description of font(s).

Instances

Show FontDescription

fontDescriptionNew :: IO FontDescription

Create a new font description.

• All field are unset.

fontDescriptionCopy :: FontDescription -> IO FontDescription

Make a deep copy of a font description.

fontDescriptionSetFamily :: GlibString string => FontDescription -> string -> IO ()

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 :: GlibString string => FontDescription -> IO (Maybe string)

Get the font family.

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

fontDescriptionSetStyle :: FontDescription -> FontStyle -> IO ()

fontDescriptionGetStyle :: FontDescription -> IO (Maybe FontStyle)

Get the style field.

fontDescriptionSetVariant :: FontDescription -> Variant -> IO ()

Set the variant field.

fontDescriptionGetVariant :: FontDescription -> IO (Maybe Variant)

Get the variant field.

fontDescriptionSetWeight :: FontDescription -> Weight -> IO ()

Set the weight field.

fontDescriptionGetWeight :: FontDescription -> IO (Maybe Weight)

Get the weight field.

fontDescriptionSetStretch :: FontDescription -> Stretch -> IO ()

Set the stretch field.

fontDescriptionGetStretch :: FontDescription -> IO (Maybe Stretch)

Get the stretch field.

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

Set the size field.

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

fontDescriptionGetSize :: FontDescription -> IO (Maybe Double)

Get the size field.

data FontMask

Flags denoting which fields in a font description are set.

Constructors

PangoFontMaskFamily

PangoFontMaskStyle

PangoFontMaskVariant

PangoFontMaskWeight

PangoFontMaskStretch

PangoFontMaskSize

PangoFontMaskGravity

Instances

Bounded FontMask

Enum FontMask

Set the style field.

• Most fonts will have either a StyleItalic or StyleOblique but rarely both.

Flags FontMask

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

Reset fields in a font description.

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

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 -> Bool

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 :: GlibString string => string -> IO FontDescription

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 :: GlibString string => FontDescription -> IO string

Convert a font description to a string.

• Creates a string representation of a font description. See fontDescriptionFromString for the format of the string.

data FontMap

Instances

Eq FontMap

Ord FontMap

GObjectClass FontMap

FontMapClass FontMap

class GObjectClass o => FontMapClass o

Instances

FontMapClass FontMap

pangoFontMapListFamilies :: FontMap -> IO [FontFamily]

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

• The FontMap can be acquired by calling cairoFontMapGetDefault.

data FontFamily

Instances

Eq FontFamily

Ord FontFamily

Show FontFamily

GObjectClass FontFamily

FontFamilyClass FontFamily

class GObjectClass o => FontFamilyClass o

Instances

FontFamilyClass FontFamily

pangoFontFamilyIsMonospace :: FontFamily -> Bool

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]

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.

data FontFace

Instances

Eq FontFace

Ord FontFace

Show FontFace

GObjectClass FontFace

FontFaceClass FontFace

class GObjectClass o => FontFaceClass o

Instances

FontFaceClass FontFace

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

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 FontDescription

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.

data Font

Instances

Eq Font

Ord Font

GObjectClass Font

FontClass Font

class GObjectClass o => FontClass o

Instances

FontClass Font