src

cursor.go (3479B)

---

 package buffer
 
 import (
 	"unicode/utf8"
 
 	"code.dwrz.net/src/pkg/editor/buffer/glyph"
 )
 
 type Cursor struct {
 	glyph int
 	index int
 	line  int
 }
 
 func (b *Buffer) Cursor() Cursor {
 	return *b.cursor
 }
 
 func (c Cursor) Glyph() int {
 	return c.glyph
 }
 
 func (c Cursor) Index() int {
 	return c.index
 }
 
 func (c Cursor) Line() int {
 	return c.line
 }
 
 func (b *Buffer) CursorDown() {
 	b.log.Debug.Printf("↓ before: %#v", b.cursor)
 	defer b.log.Debug.Printf("↓ after: %#v", b.cursor)
 
 	// If we're on the last line, don't move down.
 	if b.cursor.line >= len(b.lines)-1 {
 		return
 	}
 
 	// Move to the next line.
 	b.cursor.line++
 
 	// Adjust the column.
 	var (
 		line   = b.CursorLine()
 		length = line.Length()
 		width  = line.Width()
 	)
 	switch {
 	// If we've moved to a shorter line, snap to its end.
 	case b.cursor.glyph > width:
 		b.cursor.index = length
 		b.cursor.glyph = width
 
 	default:
 		b.cursor.index, b.cursor.glyph = line.FindGlyphIndex(
 			b.cursor.glyph,
 		)
 	}
 }
 
 func (b *Buffer) CursorLeft() {
 	b.log.Debug.Printf("← before: %#v", b.cursor)
 	defer b.log.Debug.Printf("← after: %#v", b.cursor)
 
 	switch {
 	// If we're at the beginning of the line, move to the line above;
 	// unless we're at the start of the buffer.
 	case b.cursor.index == 0 && b.cursor.line > 0:
 		b.cursor.line--
 
 		line := b.CursorLine()
 		b.cursor.index = line.Length()
 		b.cursor.glyph = line.Width()
 
 	// Move left by one rune.
 	case b.cursor.index > 0:
 		var (
 			line = b.CursorLine()
 			r    rune
 			size int
 		)
 		// Reverse until we hit the start of a rune.
 		for i := b.cursor.index - 1; i >= 0; i-- {
 			r, size = line.DecodeRune(i)
 			if r != utf8.RuneError {
 				b.cursor.index -= size
 				b.cursor.glyph -= glyph.Width(r)
 				break
 			}
 		}
 	}
 }
 
 func (b *Buffer) CursorRight() {
 	b.log.Debug.Printf("→ before: %#v", b.cursor)
 	defer b.log.Debug.Printf("→ after: %#v", b.cursor)
 
 	var (
 		line   = b.CursorLine()
 		length = line.Length()
 	)
 
 	switch {
 	// If we're at the end of the line, move to the line below;
 	// unless we're at the end of the buffer.
 	case b.cursor.index == length && b.cursor.line < len(b.lines)-1:
 		b.cursor.line++
 		b.cursor.index = 0
 		b.cursor.glyph = 0
 
 	// Move the index right by one rune.
 	case b.cursor.index < length:
 		r, size := line.DecodeRune(b.cursor.index)
 		if r == utf8.RuneError {
 			b.cursor.index++
 			b.cursor.glyph += glyph.Width(r)
 		}
 
 		b.cursor.index += size
 		b.cursor.glyph += glyph.Width(r)
 	}
 }
 
 func (b *Buffer) CursorUp() {
 	b.log.Debug.Printf("↑ before: %#v", b.cursor)
 	defer b.log.Debug.Printf("↑ after: %#v", b.cursor)
 
 	// If we're on the first line, don't move up.
 	if b.cursor.line == 0 {
 		return
 	}
 
 	b.cursor.line--
 
 	// Adjust the column.
 	var (
 		line   = b.CursorLine()
 		length = line.Length()
 		width  = line.Width()
 	)
 	switch {
 	case b.cursor.glyph > width:
 		b.cursor.index = length
 		b.cursor.glyph = width
 
 	default:
 		b.cursor.index, b.cursor.glyph = line.FindGlyphIndex(
 			b.cursor.glyph,
 		)
 	}
 }
 
 func (b *Buffer) PageDown(height int) {
 	if b.cursor.line+height > len(b.lines) {
 		b.cursor.line = len(b.lines) - 1
 	} else {
 		b.cursor.line += height
 	}
 }
 
 func (b *Buffer) PageUp(height int) {
 	if b.cursor.line-height > 0 {
 		b.cursor.line -= height
 	} else {
 		b.cursor.line = 0
 	}
 }
 
 func (b *Buffer) CursorHome() {
 	b.cursor.glyph = 0
 	b.cursor.index = 0
 }
 
 func (b *Buffer) CursorEnd() {
 	var line = b.CursorLine()
 
 	b.cursor.index = line.Length()
 	b.cursor.glyph = line.Width()
 }