1package uv
2
3// DefaultTabInterval is the default tab interval.
4const DefaultTabInterval = 8
5
6// TabStops represents horizontal line tab stops.
7type TabStops struct {
8 stops []int
9 interval int
10 width int
11}
12
13// NewTabStops creates a new set of tab stops from a number of columns and an
14// interval.
15func NewTabStops(width, interval int) *TabStops {
16 ts := new(TabStops)
17 ts.interval = interval
18 ts.width = width
19 ts.stops = make([]int, (width+(interval-1))/interval)
20 ts.init(0, width)
21 return ts
22}
23
24// DefaultTabStops creates a new set of tab stops with the default interval.
25func DefaultTabStops(cols int) *TabStops {
26 return NewTabStops(cols, DefaultTabInterval)
27}
28
29// Resize resizes the tab stops to the given width.
30func (ts *TabStops) Resize(width int) {
31 if width == ts.width {
32 return
33 }
34
35 if width < ts.width {
36 size := (width + (ts.interval - 1)) / ts.interval
37 ts.stops = ts.stops[:size]
38 } else {
39 size := (width - ts.width + (ts.interval - 1)) / ts.interval
40 ts.stops = append(ts.stops, make([]int, size)...)
41 }
42
43 ts.init(ts.width, width)
44 ts.width = width
45}
46
47// Width returns the width of the screen that the tab stops are set for.
48func (ts *TabStops) Width() int {
49 return ts.width
50}
51
52// IsStop returns true if the given column is a tab stop.
53func (ts TabStops) IsStop(col int) bool {
54 mask := ts.mask(col)
55 i := col >> 3
56 if i < 0 || i >= len(ts.stops) {
57 return false
58 }
59 return ts.stops[i]&mask != 0
60}
61
62// Next returns the next tab stop after the given column.
63func (ts TabStops) Next(col int) int {
64 return ts.Find(col, 1)
65}
66
67// Prev returns the previous tab stop before the given column.
68func (ts TabStops) Prev(col int) int {
69 return ts.Find(col, -1)
70}
71
72// Find returns the prev/next tab stop before/after the given column and delta.
73// If delta is positive, it returns the next tab stop after the given column.
74// If delta is negative, it returns the previous tab stop before the given column.
75// If delta is zero, it returns the given column.
76func (ts TabStops) Find(col, delta int) int {
77 if delta == 0 {
78 return col
79 }
80
81 var prev bool
82 count := delta
83 if count < 0 {
84 count = -count
85 prev = true
86 }
87
88 for count > 0 {
89 if !prev {
90 if col >= ts.width-1 {
91 return col
92 }
93
94 col++
95 } else {
96 if col < 1 {
97 return col
98 }
99
100 col--
101 }
102
103 if ts.IsStop(col) {
104 count--
105 }
106 }
107
108 return col
109}
110
111// Set adds a tab stop at the given column.
112func (ts *TabStops) Set(col int) {
113 mask := ts.mask(col)
114 ts.stops[col>>3] |= mask
115}
116
117// Reset removes the tab stop at the given column.
118func (ts *TabStops) Reset(col int) {
119 mask := ts.mask(col)
120 ts.stops[col>>3] &= ^mask
121}
122
123// Clear removes all tab stops.
124func (ts *TabStops) Clear() {
125 ts.stops = make([]int, len(ts.stops))
126}
127
128// mask returns the mask for the given column.
129func (ts *TabStops) mask(col int) int {
130 return 1 << (col & (ts.interval - 1))
131}
132
133// init initializes the tab stops starting from col until width.
134func (ts *TabStops) init(col, width int) {
135 for x := col; x < width; x++ {
136 if x%ts.interval == 0 {
137 ts.Set(x)
138 } else {
139 ts.Reset(x)
140 }
141 }
142}