| 🛟 Updated. 28d5985 k33g 20h ago | 1 | package syntax |
| 2 | |
| 3 | // Cache holds the spans of one source text and re-scans it only when the text |
| 4 | // has actually changed. |
| 5 | // |
| 6 | // Scanning a file is cheap but not free, and the editor redraws far more often |
| 7 | // than the text changes — every cursor move, every scroll. The revision number |
| 8 | // the buffer hands out is what tells the two apart. |
| 9 | // |
| 10 | // cache.Update(buf.Text(), buf.Revision()) |
| 11 | // for line := top; line < bottom; line++ { |
| 12 | // draw(line, cache.Line(line)) |
| 13 | // } |
| 14 | type Cache struct { |
| 15 | language Language |
| 16 | scanned bool |
| 17 | revision int |
| 18 | lines [][]Span |
| 19 | } |
| 20 | |
| 21 | // NewCache returns a cache that colours one language, or one that colours |
| 22 | // nothing for LanguageNone — which is what a file this package does not |
| 23 | // understand gets. |
| 24 | // |
| 25 | // cache := syntax.NewCache(syntax.LanguageOf(path)) |
| 26 | func NewCache(language Language) *Cache { |
| 27 | return &Cache{language: language} |
| 28 | } |
| 29 | |
| 30 | // Language returns the language this cache colours. |
| 31 | func (c *Cache) Language() Language { return c.language } |
| 32 | |
| 33 | // Enabled reports whether this cache colours anything. |
| 34 | func (c *Cache) Enabled() bool { return c.language != LanguageNone } |
| 35 | |
| 36 | // SetLanguage changes what is coloured, discarding what was scanned. Call it |
| 37 | // when the window's file changes, as Save As does. |
| 38 | func (c *Cache) SetLanguage(language Language) { |
| 39 | c.language = language |
| 40 | c.scanned = false |
| 41 | c.lines = nil |
| 42 | } |
| 43 | |
| 44 | // Update re-scans src when revision differs from the one already scanned. |
| 45 | func (c *Cache) Update(src string, revision int) { |
| 46 | if !c.Enabled() { |
| 47 | return |
| 48 | } |
| 49 | if c.scanned && c.revision == revision { |
| 50 | return |
| 51 | } |
| 52 | |
| 53 | c.lines = Highlight(c.language, src) |
| 54 | c.revision = revision |
| 55 | c.scanned = true |
| 56 | } |
| 57 | |
| 58 | // Line returns the spans of line i from the last scan, or nil when there are |
| 59 | // none — an empty line, a line past the end, or colouring turned off. |
| 60 | func (c *Cache) Line(i int) []Span { |
| 61 | if i < 0 || i >= len(c.lines) { |
| 62 | return nil |
| 63 | } |
| 64 | return c.lines[i] |
| 65 | } |
| 66 | |
| 67 | // LineCount returns how many lines the last scan covered. |
| 68 | func (c *Cache) LineCount() int { return len(c.lines) } |