| 🛟 Updated. 28d5985 k33g 21h ago | 1 | package buffer |
| 2 | |
| 3 | import "unicode" |
| 4 | |
| 5 | // Cursor returns where the insertion point currently is. |
| 6 | func (b *Buffer) Cursor() Position { return b.cursor } |
| 7 | |
| 8 | // SetCursor moves the insertion point, clamping it to a position that exists, |
| 9 | // and drops the selection — that is what an unmodified arrow key does. Use |
| 10 | // SetCursorKeepingSelection for Shift-arrow and for a mouse drag. |
| 11 | // |
| 12 | // Any pending run of typed characters stops merging into one undo step here, |
| 13 | // because a deliberate move ends the "word" being typed. |
| 14 | // |
| 15 | // b := buffer.NewFromString("hello") |
| 16 | // b.SetCursor(buffer.Position{Line: 0, Col: 99}) |
| 17 | // fmt.Println(b.Cursor().Col) // 5 |
| 18 | func (b *Buffer) SetCursor(p Position) { |
| 19 | b.cursor = b.clamp(p) |
| 20 | b.anchor = nil |
| 21 | b.coalesce = false |
| 22 | } |
| 23 | |
| 24 | // MoveLeft steps one character back, wrapping onto the end of the previous |
| 25 | // line. It is a no-op at the very start of the buffer. |
| 26 | func (b *Buffer) MoveLeft() { |
| 27 | switch { |
| 28 | case b.cursor.Col > 0: |
| 29 | b.SetCursor(Position{Line: b.cursor.Line, Col: b.cursor.Col - 1}) |
| 30 | case b.cursor.Line > 0: |
| 31 | prev := b.cursor.Line - 1 |
| 32 | b.SetCursor(Position{Line: prev, Col: len(b.lines[prev])}) |
| 33 | } |
| 34 | } |
| 35 | |
| 36 | // MoveRight steps one character forward, wrapping onto the start of the next |
| 37 | // line. It is a no-op at the very end of the buffer. |
| 38 | func (b *Buffer) MoveRight() { |
| 39 | switch { |
| 40 | case b.cursor.Col < len(b.lines[b.cursor.Line]): |
| 41 | b.SetCursor(Position{Line: b.cursor.Line, Col: b.cursor.Col + 1}) |
| 42 | case b.cursor.Line < len(b.lines)-1: |
| 43 | b.SetCursor(Position{Line: b.cursor.Line + 1, Col: 0}) |
| 44 | } |
| 45 | } |
| 46 | |
| 47 | // MoveUp steps to the previous line, keeping the column where it fits. |
| 48 | func (b *Buffer) MoveUp() { |
| 49 | b.SetCursor(Position{Line: b.cursor.Line - 1, Col: b.cursor.Col}) |
| 50 | } |
| 51 | |
| 52 | // MoveDown steps to the next line, keeping the column where it fits. |
| 53 | func (b *Buffer) MoveDown() { |
| 54 | b.SetCursor(Position{Line: b.cursor.Line + 1, Col: b.cursor.Col}) |
| 55 | } |
| 56 | |
| 57 | // MoveLineStart goes to column zero of the current line. |
| 58 | func (b *Buffer) MoveLineStart() { |
| 59 | b.SetCursor(Position{Line: b.cursor.Line, Col: 0}) |
| 60 | } |
| 61 | |
| 62 | // MoveLineEnd goes just past the last character of the current line. |
| 63 | func (b *Buffer) MoveLineEnd() { |
| 64 | b.SetCursor(Position{Line: b.cursor.Line, Col: len(b.lines[b.cursor.Line])}) |
| 65 | } |
| 66 | |
| 67 | // MoveBufferStart goes to the very first position of the text. |
| 68 | func (b *Buffer) MoveBufferStart() { |
| 69 | b.SetCursor(Position{}) |
| 70 | } |
| 71 | |
| 72 | // MoveBufferEnd goes just past the very last character of the text. |
| 73 | func (b *Buffer) MoveBufferEnd() { |
| 74 | b.SetCursor(b.wholeRange().End) |
| 75 | } |
| 76 | |
| 77 | // MoveWordLeft goes to the start of the word before the cursor, skipping over |
| 78 | // any separators in between, as Ctrl-Left does in Turbo C. |
| 79 | func (b *Buffer) MoveWordLeft() { |
| 80 | if b.cursor.Col == 0 { |
| 81 | b.MoveLeft() // wrap onto the end of the previous line, or stay put |
| 82 | return |
| 83 | } |
| 84 | |
| 85 | line := b.lines[b.cursor.Line] |
| 86 | col := b.cursor.Col |
| 87 | for col > 0 && !IsWordRune(line[col-1]) { |
| 88 | col-- |
| 89 | } |
| 90 | for col > 0 && IsWordRune(line[col-1]) { |
| 91 | col-- |
| 92 | } |
| 93 | b.SetCursor(Position{Line: b.cursor.Line, Col: col}) |
| 94 | } |
| 95 | |
| 96 | // MoveWordRight goes to the start of the word after the cursor, as Ctrl-Right |
| 97 | // does in Turbo C. |
| 98 | func (b *Buffer) MoveWordRight() { |
| 99 | line := b.lines[b.cursor.Line] |
| 100 | if b.cursor.Col >= len(line) { |
| 101 | b.MoveRight() |
| 102 | return |
| 103 | } |
| 104 | |
| 105 | col := b.cursor.Col |
| 106 | for col < len(line) && IsWordRune(line[col]) { |
| 107 | col++ |
| 108 | } |
| 109 | for col < len(line) && !IsWordRune(line[col]) { |
| 110 | col++ |
| 111 | } |
| 112 | b.SetCursor(Position{Line: b.cursor.Line, Col: col}) |
| 113 | } |
| 114 | |
| 115 | // IsWordRune reports whether r belongs to an identifier. |
| 116 | // |
| 117 | // Word movement treats a run of them as one unit, and so does the completion |
| 118 | // popup when it works out which word is being typed — which is why this is |
| 119 | // exported rather than private to the cursor. |
| 120 | // |
| 121 | // buffer.IsWordRune('_') // true |
| 122 | // buffer.IsWordRune('.') // false |
| 123 | func IsWordRune(r rune) bool { |
| 124 | return r == '_' || unicode.IsLetter(r) || unicode.IsDigit(r) |
| 125 | } |
| 126 | |
| 127 | // DisplayColumn converts a rune column on line into the screen column it |
| 128 | // occupies once tabs are expanded. |
| 129 | // |
| 130 | // b := buffer.NewFromString("\tx") |
| 131 | // fmt.Println(b.DisplayColumn(0, 1)) // 8, with the default tab width |
| 132 | func (b *Buffer) DisplayColumn(line, col int) int { |
| 133 | runes := b.lineAt(line) |
| 134 | if col < 0 { |
| 135 | col = 0 |
| 136 | } |
| 137 | if col > len(runes) { |
| 138 | col = len(runes) |
| 139 | } |
| 140 | |
| 141 | screen := 0 |
| 142 | for _, r := range runes[:col] { |
| 143 | if r == '\t' { |
| 144 | screen += b.tabWidth - screen%b.tabWidth |
| 145 | } else { |
| 146 | screen++ |
| 147 | } |
| 148 | } |
| 149 | return screen |
| 150 | } |
| 151 | |
| 152 | // RuneColumn is the inverse of DisplayColumn: it maps a screen column back to |
| 153 | // the rune column the cursor should sit at, which is what a mouse click needs. |
| 154 | func (b *Buffer) RuneColumn(line, screenCol int) int { |
| 155 | runes := b.lineAt(line) |
| 156 | |
| 157 | screen := 0 |
| 158 | for i, r := range runes { |
| 159 | width := 1 |
| 160 | if r == '\t' { |
| 161 | width = b.tabWidth - screen%b.tabWidth |
| 162 | } |
| 163 | // A click in the second half of a wide tab lands on the next rune. |
| 164 | if screenCol < screen+width { |
| 165 | return i |
| 166 | } |
| 167 | screen += width |
| 168 | } |
| 169 | return len(runes) |
| 170 | } |