feat(position): Add function to place an overlay (from lipgoss PR cha…

…rmbracelet#102)

go.mod

@@ -6,6 +6,9 @@ go 1.18
 
 require (
 	github.com/charmbracelet/x/exp/term v0.0.0-20240408110044-525ba71bb562
+	github.com/mattn/go-runewidth v0.0.15
+	github.com/muesli/ansi v0.0.0-20230316100256-276c6243b2f6
+	github.com/muesli/reflow v0.3.0
 	github.com/muesli/termenv v0.15.2
 	github.com/rivo/uniseg v0.4.7
 )
@@ -14,6 +17,5 @@ require (
 	github.com/aymanbagabas/go-osc52/v2 v2.0.1 // indirect
 	github.com/lucasb-eyer/go-colorful v1.2.0 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
-	github.com/mattn/go-runewidth v0.0.15 // indirect
 	golang.org/x/sys v0.19.0 // indirect
 )

go.sum

@@ -6,10 +6,16 @@ github.com/lucasb-eyer/go-colorful v1.2.0 h1:1nnpGOrhyZZuNyfu1QjKiUICQ74+3FNCN69
 github.com/lucasb-eyer/go-colorful v1.2.0/go.mod h1:R4dSotOR9KMtayYi1e77YzuveK+i7ruzyGqttikkLy0=
 github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWEY=
 github.com/mattn/go-isatty v0.0.20/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
+github.com/mattn/go-runewidth v0.0.12/go.mod h1:RAqKPSqVFrSLVXbA8x7dzmKdmGzieGRCM46jaSJTDAk=
 github.com/mattn/go-runewidth v0.0.15 h1:UNAjwbU9l54TA3KzvqLGxwWjHmMgBUVhBiTjelZgg3U=
 github.com/mattn/go-runewidth v0.0.15/go.mod h1:Jdepj2loyihRzMpdS35Xk/zdY8IAYHsh153qUoGf23w=
+github.com/muesli/ansi v0.0.0-20230316100256-276c6243b2f6 h1:ZK8zHtRHOkbHy6Mmr5D264iyp3TiX5OmNcI5cIARiQI=
+github.com/muesli/ansi v0.0.0-20230316100256-276c6243b2f6/go.mod h1:CJlz5H+gyd6CUWT45Oy4q24RdLyn7Md9Vj2/ldJBSIo=
+github.com/muesli/reflow v0.3.0 h1:IFsN6K9NfGtjeggFP+68I4chLZV2yIKsXJFNZ+eWh6s=
+github.com/muesli/reflow v0.3.0/go.mod h1:pbwTDkVPibjO2kyvBQRBxTWEEGDGq0FlB1BIKtnHY/8=
 github.com/muesli/termenv v0.15.2 h1:GohcuySI0QmI3wN8Ok9PtKGkgkFIk7y6Vpb5PvrY+Wo=
 github.com/muesli/termenv v0.15.2/go.mod h1:Epx+iuz8sNs7mNKhxzH4fWXGNpZwUaJKRS1noLXviQ8=
+github.com/rivo/uniseg v0.1.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
 github.com/rivo/uniseg v0.2.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
 github.com/rivo/uniseg v0.4.7 h1:WUdvkW8uEhrYfLC4ZzdpI2ztxP1I582+49Oc5Mq64VQ=
 github.com/rivo/uniseg v0.4.7/go.mod h1:FN3SvrM+Zdj16jyLfmOkMNblXMcoc8DfTHruCPUcx88=

position.go

@@ -1,10 +1,13 @@
 package lipgloss
 
 import (
+  "bytes"
 	"math"
 	"strings"
 
-	"github.com/charmbracelet/x/exp/term/ansi"
+  "github.com/mattn/go-runewidth"
+	"github.com/muesli/ansi"
+  "github.com/muesli/reflow/truncate"
 )
 
 // Position represents a position along a horizontal or vertical axis. It's in
@@ -66,7 +69,7 @@ func (r *Renderer) PlaceHorizontal(width int, pos Position, str string, opts ...
 	var b strings.Builder
 	for i, l := range lines {
 		// Is this line shorter than the longest line?
-		short := max(0, contentWidth-ansi.StringWidth(l))
+		short := max(0, ansi.PrintableRuneWidth(l))
 
 		switch pos { //nolint:exhaustive
 		case Left:
@@ -152,3 +155,106 @@ func (r *Renderer) PlaceVertical(height int, pos Position, str string, opts ...W
 
 	return b.String()
 }
+
+// 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)
+}