diff --git a/ui/helpers/helpers.go b/ui/helpers/helpers.go new file mode 100644 index 0000000..2cced8e --- /dev/null +++ b/ui/helpers/helpers.go @@ -0,0 +1,185 @@ +package helpers + +import ( + "bytes" + "strings" + + "github.com/mattn/go-runewidth" + "github.com/muesli/ansi" + "github.com/muesli/reflow/truncate" + "github.com/muesli/termenv" +) + +// Most of this code is borrowed from +// https://github.com/charmbracelet/lipgloss/pull/102 +// as well as the lipgloss library. + +// Split a string into lines, additionally returning the size of the widest +// line. +func getLines(s string) (lines []string, widest int) { + lines = strings.Split(s, "\n") + + for _, l := range lines { + w := ansi.PrintableRuneWidth(l) + if widest < w { + widest = w + } + } + + return lines, widest +} + +// PlaceOverlay places fg on top of bg. +func PlaceOverlay(x, y int, fg, bg string, opts ...WhitespaceOption) string { + fgLines, fgWidth := getLines(fg) + bgLines, bgWidth := getLines(bg) + bgHeight := len(bgLines) + fgHeight := len(fgLines) + + if fgWidth >= bgWidth && fgHeight >= bgHeight { + // FIXME: return fg or bg? + return fg + } + // TODO: allow placement outside of the bg box? + x = clamp(x, 0, bgWidth-fgWidth) + y = clamp(y, 0, bgHeight-fgHeight) + + ws := &whitespace{} + for _, opt := range opts { + opt(ws) + } + + var b strings.Builder + for i, bgLine := range bgLines { + if i > 0 { + b.WriteByte('\n') + } + if i < y || i >= y+fgHeight { + b.WriteString(bgLine) + continue + } + + pos := 0 + if x > 0 { + left := truncate.String(bgLine, uint(x)) + pos = ansi.PrintableRuneWidth(left) + b.WriteString(left) + if pos < x { + b.WriteString(ws.render(x - pos)) + pos = x + } + } + + fgLine := fgLines[i-y] + b.WriteString(fgLine) + pos += ansi.PrintableRuneWidth(fgLine) + + right := cutLeft(bgLine, pos) + bgWidth := ansi.PrintableRuneWidth(bgLine) + rightWidth := ansi.PrintableRuneWidth(right) + if rightWidth <= bgWidth-pos { + b.WriteString(ws.render(bgWidth - rightWidth - pos)) + } + + b.WriteString(right) + } + + return b.String() +} + +// cutLeft cuts printable characters from the left. +// This function is heavily based on muesli's ansi and truncate packages. +func cutLeft(s string, cutWidth int) string { + var ( + pos int + isAnsi bool + ab bytes.Buffer + b bytes.Buffer + ) + for _, c := range s { + var w int + if c == ansi.Marker || isAnsi { + isAnsi = true + ab.WriteRune(c) + if ansi.IsTerminator(c) { + isAnsi = false + if bytes.HasSuffix(ab.Bytes(), []byte("[0m")) { + ab.Reset() + } + } + } else { + w = runewidth.RuneWidth(c) + } + + if pos >= cutWidth { + if b.Len() == 0 { + if ab.Len() > 0 { + b.Write(ab.Bytes()) + } + if pos-cutWidth > 1 { + b.WriteByte(' ') + continue + } + } + b.WriteRune(c) + } + pos += w + } + return b.String() +} + +func clamp(v, lower, upper int) int { + return min(max(v, lower), upper) +} + +func max(a, b int) int { + if a > b { + return a + } + return b +} + +func min(a, b int) int { + if a < b { + return a + } + return b +} + +type whitespace struct { + style termenv.Style + chars string +} + +// Render whitespaces. +func (w whitespace) render(width int) string { + if w.chars == "" { + w.chars = " " + } + + r := []rune(w.chars) + j := 0 + b := strings.Builder{} + + // Cycle through runes and print them into the whitespace. + for i := 0; i < width; { + b.WriteRune(r[j]) + j++ + if j >= len(r) { + j = 0 + } + i += ansi.PrintableRuneWidth(string(r[j])) + } + + // Fill any extra gaps white spaces. This might be necessary if any runes + // are more than one cell wide, which could leave a one-rune gap. + short := width - ansi.PrintableRuneWidth(b.String()) + if short > 0 { + b.WriteString(strings.Repeat(" ", short)) + } + + return w.style.Styled(b.String()) +} + +// WhitespaceOption sets a styling rule for rendering whitespace. +type WhitespaceOption func(*whitespace)