first working commit

widgets/pager/pager.go

@@ -0,0 +1,171 @@
+// This is a "fork" of Vaxis' pager widget that adds Unicode line breaking.
+// See <https://git.sr.ht/~rockorager/vaxis/tree/v0.15.0/item/widgets/pager/pager.go>.
+
+package pager
+
+import (
+	"strings"
+
+	"git.sr.ht/~rockorager/vaxis"
+	"github.com/rivo/uniseg"
+)
+
+const (
+	WrapFast = iota
+	WrapWords
+)
+
+var defaultFill = vaxis.Character{Grapheme: " "}
+
+type Model struct {
+	Segments []vaxis.Segment
+	lines    []*line
+	Fill     vaxis.Cell
+	Offset   int
+	WrapMode int
+	width    int
+}
+
+type line struct {
+	characters []vaxis.Cell
+}
+
+func (l *line) append(t vaxis.Cell) {
+	l.characters = append(l.characters, t)
+}
+
+func (m *Model) Draw(win vaxis.Window) {
+	w, h := win.Size()
+	if w != m.width {
+		m.width = w
+		m.Layout()
+	}
+	if len(m.lines)-m.Offset < h {
+		m.Offset = len(m.lines) - h
+	}
+	if m.Offset < 0 {
+		m.Offset = 0
+	}
+	if m.Fill.Grapheme == "" {
+		m.Fill.Character = defaultFill
+	}
+	win.Fill(m.Fill)
+	for row, l := range m.lines {
+		if row < m.Offset {
+			continue
+		}
+		if (row - m.Offset) >= h {
+			return
+		}
+		col := 0
+		for _, cell := range l.characters {
+			win.SetCell(col, row-m.Offset, cell)
+			col += cell.Width
+		}
+	}
+}
+
+func (m *Model) layoutFast() {
+	l := &line{}
+	col := 0
+	for _, seg := range m.Segments {
+		for _, char := range vaxis.Characters(seg.Text) {
+			if strings.ContainsRune(char.Grapheme, '\n') {
+				m.lines = append(m.lines, l)
+				l = &line{}
+				col = 0
+				continue
+			}
+			cell := vaxis.Cell{
+				Character: char,
+				Style:     seg.Style,
+			}
+			l.append(cell)
+			col += char.Width
+			if col >= m.width {
+				m.lines = append(m.lines, l)
+				l = &line{}
+				col = 0
+			}
+		}
+	}
+}
+
+func (m *Model) layoutSlow() {
+	cols := m.width
+	col := 0
+	l := &line{}
+
+	var (
+		state   = -1
+		segment string
+	)
+
+	for _, seg := range m.Segments {
+		rest := seg.Text
+		for len(rest) > 0 {
+			segment, rest, _, state = uniseg.FirstLineSegmentInString(rest, state)
+			chars := vaxis.Characters(segment)
+			total := 0
+			for _, char := range chars {
+				total += char.Width
+			}
+
+			switch {
+			case total > cols:
+			case total+col > cols:
+				m.lines = append(m.lines, l)
+				l = &line{}
+				col = 0
+			default:
+			}
+
+			for _, char := range chars {
+				if uniseg.HasTrailingLineBreakInString(char.Grapheme) {
+					m.lines = append(m.lines, l)
+					l = &line{}
+					col = 0
+					continue
+				}
+				cell := vaxis.Cell{
+					Character: char,
+					Style:     seg.Style,
+				}
+				l.append(cell)
+				col += char.Width
+				if col >= cols {
+					m.lines = append(m.lines, l)
+					l = &line{}
+					col = 0
+				}
+			}
+		}
+	}
+}
+
+func (m *Model) Layout() {
+	m.lines = []*line{}
+	switch m.WrapMode {
+	case WrapFast:
+		m.layoutFast()
+	case WrapWords:
+		m.layoutSlow()
+	}
+}
+
+// Scrolls the pager down n lines, if it can
+func (m *Model) ScrollDown() {
+	m.Offset += 1
+}
+
+func (m *Model) ScrollUp() {
+	m.Offset -= 1
+}
+
+func (m *Model) ScrollDownN(n int) {
+	m.Offset += n
+}
+
+func (m *Model) ScrollUpN(n int) {
+	m.Offset -= n
+}