Documentation
¶
Overview ¶
Package fontres implements the font resolution chain, metrics, and word wrap of doc/template.md#font-resolution.
Index ¶
- Constants
- func LineWidth(face *Face, line string) float64
- func TextHeight(face *Face, lines int) float64
- func Wrap(face *Face, text string, width float64) []string
- type Face
- func (face *Face) Advance(char rune) float64
- func (face *Face) AdvanceUnits(char rune) (float64, bool)
- func (face *Face) FaceIndex() int
- func (face *Face) Glyph(char rune) (uint16, bool)
- func (face *Face) GlyphAdvance(gid uint16) float64
- func (face *Face) Key() string
- func (face *Face) Leading() float64
- func (face *Face) MissingRunes() []rune
- func (face *Face) UnderlineMetrics() (offset, thickness float64)
- func (face *Face) Upem() float64
- func (face *Face) VerticalMetrics() (ascender, descender float64)
- func (face *Face) Width(text string) float64
- type FaceInfo
- type Request
- type ResolvedBy
- type Resolver
- type Style
Constants ¶
const LeadingRatio = 1.2
LeadingRatio is the baseline-to-baseline distance as a multiple of the font size.
A constant multiplier is predictable and font-independent, which is what a paginating engine wants: line spacing must not change when a typeface is substituted, because that changes what fits on a page.
The font's own suggestion -- hhea ascent + descent + lineGap -- is per-face and does exactly that.
Variables ¶
This section is empty.
Functions ¶
func TextHeight ¶
TextHeight is the height a run of lines occupies.
func Wrap ¶
Wrap breaks text into lines that fit a box of the given width.
Breaking is greedy and by word: the longest run of words that fits goes on the line. A single word wider than the box is broken by character, since the alternative is a line that overflows silently. Explicit newlines in the text always break.
Trailing spaces at a break are dropped, so a line's measured width is the width of what is drawn.
Types ¶
type Face ¶
type Face struct {
// Name is the template's name for this font.
Name string
Size int
Bold bool
Italic bool
Underline bool
// Requested is the template's typeface,
// absent when the template pinned a file or a data blob.
Requested string
ResolvedFile string
ResolvedData string
ResolvedFace string
ResolvedBy ResolvedBy
// contains filtered or unexported fields
}
Face is a resolved font at a size, and the only thing the engine measures with.
func Load ¶
Load parses a font file for measuring, outside the resolution chain.
A renderer takes this path: the printout already names the file and the face inside it, so there is nothing left to resolve, and measuring through the same code as the engine is what keeps the two agreeing.
func (*Face) Advance ¶
Advance returns a rune's advance width in points at the face's size.
Advance means hmtx throughout: the engine does not kern and does not shape, so this is the only notion of advance it has, and a renderer must be told to match. A rune the font lacks measures the .notdef glyph, which is the visible empty box the specification asks for, and is recorded as missing.
func (*Face) AdvanceUnits ¶
AdvanceUnits returns a rune's advance in font units, which is what a monospace check compares.
func (*Face) FaceIndex ¶
FaceIndex is the face's position inside the file it was parsed from, which is 0 for every file that is not a collection.
The printout carries it so that a renderer, handed nothing but the document, opens the same face out of a collection that the engine measured with.
func (*Face) Glyph ¶
Glyph maps a rune to a glyph index, reporting whether the font has it.
The mapping comes from the same cmap the engine measured through, which is what keeps a renderer's glyph choice and the printout's metrics describing one font.
func (*Face) GlyphAdvance ¶
GlyphAdvance returns a glyph's advance in font units.
func (*Face) MissingRunes ¶
MissingRunes lists the characters this face was asked for and does not have. The order is by code point rather than the map's, so that a font missing more than one glyph produces the same warning sequence on every run.
func (*Face) UnderlineMetrics ¶
UnderlineMetrics returns the underline's offset below the baseline and its thickness, in font units.
func (*Face) Upem ¶
Upem is the face's units per em, the denominator every font-unit metric below is expressed in.
func (*Face) VerticalMetrics ¶
VerticalMetrics returns the ascender and descender in font units, the descender positive downward.
They position the baseline inside the leading the printout carries; they do not decide the leading, which is a constant multiple of the size.
type FaceInfo ¶
type FaceInfo struct {
File string
Index int
// Family is name ID 16 where the font has one, and name ID 1 otherwise.
Family string
// Subfamily is name ID 17 or 2, read only as a last resort.
Subfamily string
Style Style
Font *gofont.Font
// Ascender and Descender are the face's hhea metrics in font units,
// the descender positive downward. Both are zero for a face without
// an hhea table.
Ascender, Descender float64
}
FaceInfo describes one face inside a font file.
type Request ¶
type Request struct {
Name string
Typeface string
File string
Data string
Size int
Bold bool
Italic bool
Underline bool
}
Request is one `font` node: what the template asked for.
type ResolvedBy ¶
type ResolvedBy string
ResolvedBy names the step of the resolution chain that produced a face.
const ( ByExplicit ResolvedBy = "explicit" ByHost ResolvedBy = "host" ByAlias ResolvedBy = "alias" BySubstitute ResolvedBy = "substitute" )
Resolution steps, as the printout spells them.
type Resolver ¶
type Resolver struct {
// Strict stops resolution after an explicit file or data blob
// and fails with the unresolved typeface named.
Strict bool
// BaseDir resolves a relative `font file=`.
BaseDir string
// Blob returns a named data blob's bytes.
Blob func(name string) ([]byte, bool)
// Dirs overrides the machine's font directories. Empty means
// the platform's own, which is what a build uses; a test points it
// at a fixture directory so that the chain can be exercised without
// depending on what is installed.
Dirs []string
// Diagnostics describe the machine rather than the document --
// a font file that could not be used, or two faces claiming one key.
// They are surfaced by validation and by the library's hook,
// and never enter a printout's warning list.
Diagnostics []string
// Warnings describe the document: a typeface that reached the substitute,
// or a candidate substitute that is not in fact monospaced.
Warnings []string
// contains filtered or unexported fields
}
Resolver resolves font requests, caching what it finds.
func NewResolver ¶
NewResolver builds a resolver.
func (*Resolver) HostFamilies ¶
HostFamilies lists the families the machine offers, for diagnostics.
Source Files