1 // SPDX-License-Identifier: Unlicense OR MIT
2 3 package text
4 5 import (
6 "io"
7 8 "golang.org/x/image/math/fixed"
9 10 "github.com/p9c/p9/pkg/gel/gio/op"
11 )
12 13 // A Line contains the measurements of a line of text.
14 type Line struct {
15 Layout Layout
16 // Width is the width of the line.
17 Width fixed.Int26_6
18 // Ascent is the height above the baseline.
19 Ascent fixed.Int26_6
20 // Descent is the height below the baseline, including
21 // the line gap.
22 Descent fixed.Int26_6
23 // Bounds is the visible bounds of the line.
24 Bounds fixed.Rectangle26_6
25 }
26 27 type Layout struct {
28 Text string
29 Advances []fixed.Int26_6
30 }
31 32 // Style is the font style.
33 type Style int
34 35 // Weight is a font weight, in CSS units subtracted 400 so the zero value
36 // is normal text weight.
37 type Weight int
38 39 // Font specify a particular typeface variant, style and weight.
40 type Font struct {
41 Typeface Typeface
42 Variant Variant
43 Style Style
44 // Weight is the text weight. If zero, Normal is used instead.
45 Weight Weight
46 }
47 48 // Face implements text layout and shaping for a particular font. All
49 // methods must be safe for concurrent use.
50 type Face interface {
51 Layout(ppem fixed.Int26_6, maxWidth int, txt io.Reader) ([]Line, error)
52 Shape(ppem fixed.Int26_6, str Layout) op.CallOp
53 }
54 55 // Typeface identifies a particular typeface design. The empty
56 // string denotes the default typeface.
57 type Typeface string
58 59 // Variant denotes a typeface variant such as "Mono" or "Smallcaps".
60 type Variant string
61 62 type Alignment uint8
63 64 const (
65 Start Alignment = iota
66 End
67 Middle
68 )
69 70 const (
71 Regular Style = iota
72 Italic
73 )
74 75 const (
76 Normal Weight = 400 - 400
77 Medium Weight = 500 - 400
78 Bold Weight = 600 - 400
79 )
80 81 func (a Alignment) String() string {
82 switch a {
83 case Start:
84 return "Start"
85 case End:
86 return "End"
87 case Middle:
88 return "Middle"
89 default:
90 panic("unreachable")
91 }
92 }
93