feat: add saveCanvasToText primitive

Author: xaviergodart

internal/canvas/canvas.go

@@ -87,6 +87,7 @@ type Canvas struct {
 	isFilling    bool
 	IsLooping    bool
 	save         bool
+	saveText     bool
 	autoResize   bool
 	disabled     bool
 }
@@ -180,6 +181,10 @@ func (c *Canvas) render() {
 		c.exportCanvasToPNG(content)
 		c.save = false
 	}
+	if c.saveText {
+		c.exportCanvasToText(content)
+		c.saveText = false
+	}
 	if c.frames != nil {
 		c.recordFrame(content)
 	}

internal/canvas/canvas_test.go

@@ -3,6 +3,9 @@ package canvas
 import (
 	"fmt"
 	"math"
+	"os"
+	"path/filepath"
+	"strings"
 	"testing"
 	"time"
 )
@@ -303,3 +306,26 @@ func TestBalancedPushDoesNotWarn(t *testing.T) {
 		t.Errorf("debugBuffer = %v, want empty", c.debugBuffer)
 	}
 }
+
+// The exported text must contain the drawn characters but none of the
+// ANSI color escapes used to render them.
+func TestSaveCanvasToText(t *testing.T) {
+	c := mockCanvas(5, 5)
+	c.Rect(0, 0, 3, 3)
+
+	filename := filepath.Join(t.TempDir(), "out.txt")
+	c.saveText = true
+	c.saveFilename = filename
+	c.render()
+
+	got, err := os.ReadFile(filename)
+	if err != nil {
+		t.Fatalf("can't read exported text file: %v", err)
+	}
+	if strings.Contains(string(got), "\x1b") {
+		t.Errorf("exported text contains an ANSI escape: %q", got)
+	}
+	if !strings.Contains(string(got), c.strokeText) {
+		t.Errorf("exported text = %q, want it to contain the drawn stroke %q", got, c.strokeText)
+	}
+}

internal/canvas/capture.go

@@ -9,8 +9,10 @@ import (
 	"image/png"
 	"math"
 	"os"
+	"strings"
 
 	"github.com/charmbracelet/log"
+	"github.com/charmbracelet/x/ansi"
 
 	ansitoimage "github.com/xaviergodart/go-ansi-to-image"
 )
@@ -22,6 +24,14 @@ func (c *Canvas) SaveCanvasToPNG(filename string) {
 	c.Redraw()
 }
 
+// SaveCanvasToText exports the canvas to a plain text file, dropping
+// all color information.
+func (c *Canvas) SaveCanvasToText(filename string) {
+	c.saveText = true
+	c.saveFilename = filename
+	c.Redraw()
+}
+
 // SaveCanvasToGIF exports the canvas to an animated gif
 // for a given duration (in seconds).
 func (c *Canvas) SaveCanvasToGIF(filename string, duration int) {
@@ -133,6 +143,14 @@ func (c *Canvas) exportCanvasToPNG(frame string) {
 	}
 }
 
+func (c *Canvas) exportCanvasToText(frame string) {
+	fmt.Fprintln(c.output, "Saving text...")
+	text := strings.ReplaceAll(ansi.Strip(frame), "\r\n", "\n")
+	if err := os.WriteFile(c.saveFilename, []byte(text), 0o644); err != nil {
+		c.captureFailed(fmt.Errorf("can't create text file: %w", err))
+	}
+}
+
 func gifDelay(fps int) int {
 	return max(int(math.Round(100/float64(clamp(fps, minFPS, maxFPS)))), 1)
 }