fix: cellrenderer: reset cursor when at phantom cell

cell_renderer.go

@@ -417,10 +417,10 @@ func (c *cellRenderer) changes() {
 	}
 
 	height := c.scr.Height()
-	var x int
 	if *c.lastRender == "" {
 		// We render the changes line by line to be able to get the cursor
 		// position using the width of each line.
+		var x int
 		for y := 0; y < height; y++ {
 			var line string
 			x, line = cellbuf.RenderLine(c.scr, y)
@@ -537,7 +537,6 @@ func (c *cellRenderer) flushSegment(seg *cellbuf.Segment, to image.Point, eraser
 		erased = true
 	} else {
 		c.renderSegment(seg)
-		c.scr.cur.X += seg.Width
 	}
 	return
 }
@@ -567,6 +566,14 @@ func (c *cellRenderer) renderSegment(seg *cellbuf.Segment) {
 	}
 
 	c.buf.WriteString(seg.Content)
+	c.scr.cur.X += seg.Width
+
+	if c.scr.cur.X >= c.scr.Width() {
+		// NOTE: We need to reset the cursor when at phantom cell i.e. outside
+		// the screen, otherwise, the cursor position will be out of sync.
+		c.scr.cur.X = 0
+		c.buf.WriteByte(ansi.CR)
+	}
 }
 
 // moveCursor moves the cursor to the given position.
@@ -607,9 +614,9 @@ func (c *cellRenderer) moveCursor(x, y int) {
 				if dx >= 3 {
 					// [ansi.CursorLeft] is at least 3 bytes long, so we use [ansi.BS]
 					// when we can to avoid writing more bytes than necessary.
-					c.buf.WriteString(ansi.CursorLeft(c.scr.cur.X - x))
+					c.buf.WriteString(ansi.CursorLeft(dx))
 				} else {
-					c.buf.Write(bytes.Repeat([]byte{ansi.BS}, dx))
+					c.buf.WriteString(strings.Repeat("\b", dx))
 				}
 			}
 		}