history_read.go RawHistoryFolder

1package vt
2
3import renderer "github.com/bnema/vev-vt/core"
4
5// RowWidth returns the retained width of row y, or zero outside the view.
6// Unlike Row, it does not allocate or decode a semantic row.
7func (v HistoryView) RowWidth(y int) int {
8	chunk, _ := v.locateRow(y)
9	if chunk == nil {
10		return 0
11	}
12	return chunk.width
13}
14
15// Cell returns one semantic cell without allocating a row. Coordinates follow
16// Screen.Cell: x is the column and y is the row. Invalid coordinates return the
17// canonical blank cell. Variable-width history does not implement CellSource.
18func (v HistoryView) Cell(x, y int) renderer.Cell {
19	chunk, row := v.locateRow(y)
20	if chunk == nil || x < 0 || x >= chunk.width {
21		return renderer.BlankCell()
22	}
23	return chunk.cell(row, x)
24}
25
26// CopyRow copies up to len(dst) cells into caller-owned storage and returns the
27// number copied. It neither allocates a row nor exposes mutable page storage.
28func (v HistoryView) CopyRow(y int, dst []renderer.Cell) int {
29	chunk, row := v.locateRow(y)
30	if chunk == nil {
31		return 0
32	}
33	n := min(len(dst), chunk.width)
34	frame := chunk.frameView()
35	for x := range n {
36		dst[x] = frame.Cell(x, chunk.start+row)
37	}
38	return n
39}
40
41// RangeText streams each row's text in order without allocating per row. For
42// row i of the given cell width, runes holds one rune per non-continuation
43// cell (zero runes read as a space) and columns holds the cell column of each
44// rune. Both slices are only valid during the callback. Like Range, it
45// restores at most one cold page at a time and does not populate the page
46// cache.
47func (v HistoryView) RangeText(yield func(i int, runes []rune, columns []int, width int) bool) error {
48	var runes []rune
49	var columns []int
50	i := 0
51	for _, chunk := range v.chunks {
52		frame, err := chunk.page.readFrame(false)
53		if err != nil {
54			return err
55		}
56		for row := range chunk.len() {
57			runes, columns = frame.AppendRowText(runes[:0], columns[:0], chunk.start+row)
58			if !yield(i, runes, columns, chunk.width) {
59				return nil
60			}
61			i++
62		}
63	}
64	return nil
65}
66
67func (v HistoryView) locateRow(y int) (*HistoryChunk, int) {
68	if y < 0 {
69		return nil, 0
70	}
71	for _, chunk := range v.chunks {
72		if y < chunk.len() {
73			return chunk, y
74		}
75		y -= chunk.len()
76	}
77	return nil, 0
78}