Add --wrap option and 'toggle-wrap' action (#3887)

* `--wrap`
* `--wrap-sign`
* `toggle-wrap`

Close #3619
Close #2236
Close #577
Close #461

2 files changed, 120 insertions, 1 deletions

diff --git a/src/util/chars.go b/src/util/chars.go
index 82773f40..a0ea9436 100644
--- a/src/util/chars.go
+++ b/src/util/chars.go
@@ -226,3 +226,85 @@ func (chars *Chars) Prepend(prefix string) {
 		chars.slice = append([]byte(prefix), chars.slice...)
 	}
 }
+
+func (chars *Chars) Lines(multiLine bool, maxLines int, wrapCols int, wrapSignWidth int, tabstop int) ([][]rune, bool) {
+	text := make([]rune, chars.Length())
+	copy(text, chars.ToRunes())
+
+	lines := [][]rune{}
+	overflow := false
+	if !multiLine {
+		lines = append(lines, text)
+	} else {
+		from := 0
+		for off := 0; off < len(text); off++ {
+			if text[off] == '\n' {
+				lines = append(lines, text[from:off+1]) // Include '\n'
+				from = off + 1
+				if len(lines) >= maxLines {
+					break
+				}
+			}
+		}
+
+		var lastLine []rune
+		if from < len(text) {
+			lastLine = text[from:]
+		}
+
+		overflow = false
+		if len(lines) >= maxLines {
+			overflow = true
+		} else {
+			lines = append(lines, lastLine)
+		}
+	}
+
+	// If wrapping is disabled, we're done
+	if wrapCols == 0 {
+		return lines, overflow
+	}
+
+	wrapped := [][]rune{}
+	for _, line := range lines {
+		// Remove trailing '\n' and remember if it was there
+		newline := len(line) > 0 && line[len(line)-1] == '\n'
+		if newline {
+			line = line[:len(line)-1]
+		}
+
+		for {
+			cols := wrapCols
+			if len(wrapped) > 0 {
+				cols -= wrapSignWidth
+			}
+			_, overflowIdx := RunesWidth(line, 0, tabstop, cols)
+			if overflowIdx >= 0 {
+				// Might be a wide character
+				if overflowIdx == 0 {
+					overflowIdx = 1
+				}
+				if len(wrapped) >= maxLines {
+					return wrapped, true
+				}
+				wrapped = append(wrapped, line[:overflowIdx])
+				line = line[overflowIdx:]
+				continue
+			}
+
+			// Restore trailing '\n'
+			if newline {
+				line = append(line, '\n')
+			}
+
+			if len(wrapped) >= maxLines {
+				return wrapped, true
+			}
+
+			wrapped = append(wrapped, line)
+			break
+		}
+	}
+
+	return wrapped, false
+}
diff --git a/src/util/chars_test.go b/src/util/chars_test.go
index b7983f30..0d3e4f37 100644
--- a/src/util/chars_test.go
+++ b/src/util/chars_test.go
@@ -1,6 +1,9 @@
 package util
 
-import "testing"
+import (
+	"fmt"
+	"testing"
+)
 
 func TestToCharsAscii(t *testing.T) {
 	chars := ToChars([]byte("foobar"))
@@ -44,3 +47,37 @@ func TestTrimLength(t *testing.T) {
 	check("  h   o  ", 5)
 	check("         ", 0)
 }
+
+func TestCharsLines(t *testing.T) {
+	chars := ToChars([]byte("abcdef\n가나다\n\tdef"))
+	check := func(multiLine bool, maxLines int, wrapCols int, wrapSignWidth int, tabstop int, expectedNumLines int, expectedOverflow bool) {
+		lines, overflow := chars.Lines(multiLine, maxLines, wrapCols, wrapSignWidth, tabstop)
+		fmt.Println(lines, overflow)
+		if len(lines) != expectedNumLines || overflow != expectedOverflow {
+			t.Errorf("Invalid result: %d %v (expected %d %v)", len(lines), overflow, expectedNumLines, expectedOverflow)
+		}
+	}
+
+	// No wrap
+	check(true, 1, 0, 0, 8, 1, true)
+	check(true, 2, 0, 0, 8, 2, true)
+	check(true, 3, 0, 0, 8, 3, false)
+
+	// Wrap (2)
+	check(true, 4, 2, 0, 8, 4, true)
+	check(true, 5, 2, 0, 8, 5, true)
+	check(true, 6, 2, 0, 8, 6, true)
+	check(true, 7, 2, 0, 8, 7, true)
+	check(true, 8, 2, 0, 8, 8, true)
+	check(true, 9, 2, 0, 8, 9, false)
+	check(true, 9, 2, 0, 1, 8, false) // Smaller tab size
+
+	// With wrap sign (3 + 1)
+	check(true, 100, 3, 1, 1, 8, false)
+
+	// With wrap sign (3 + 2)
+	check(true, 100, 3, 2, 1, 12, false)
+
+	// With wrap sign (3 + 2) and no multi-line
+	check(false, 100, 3, 2, 1, 13, false)
+}