Fix line wrapping when multi-cell runes are involved

Author: stefanhaller

view.go

@@ -1523,7 +1523,10 @@ func lineWrap(line []cell, columns int) [][]cell {
 				}
 				// Either way, continue *after* the break
 				offset = lastWhitespaceIndex + 1
-				n = i - offset + 1
+				n = 0
+				for _, c := range line[offset : i+1] {
+					n += runewidth.RuneWidth(c.chr)
+				}
 			} else {
 				// in this case we're breaking mid-word
 				lines = append(lines, line[offset:i])

view_test.go

@@ -241,16 +241,10 @@ func TestLineWrap(t *testing.T) {
 			line:    "🐤🐤🐤 🐝🐝 🙉 🦊🦊🦊-🐬🐬 🦢🦢",
 			columns: 9,
 			expected: []string{
-				/* EXPECTED:
 				"🐤🐤🐤",
 				"🐝🐝 🙉",
 				"🦊🦊🦊-",
 				"🐬🐬 🦢🦢",
-				ACTUAL: */
-				"🐤🐤🐤",
-				"🐝🐝 🙉",
-				"🦊🦊🦊-🐬🐬",
-				"🦢🦢",
 			},
 		},
 		{