Add SplitText() method for splitting utf-8 strings constrained by rendered width

2 files changed, 57 insertions, 0 deletions

diff --git a/fpdf.go b/fpdf.go
index 7bee6e5..d3366ce 100644
--- a/fpdf.go
+++ b/fpdf.go
@@ -2407,6 +2407,9 @@ func (f *Fpdf) Cellf(w, h float64, fmtStr string, args ...interface{}) {
 // used to determine the total height of wrapped text for vertical placement
 // purposes.
 //
+// This method is useful for codepage-based fonts only. For UTF-8 encoded text,
+// use SplitText().
+//
 // You can use MultiCell if you want to print a text on several lines in a
 // simple way.
 func (f *Fpdf) SplitLines(txt []byte, w float64) [][]byte {
diff --git a/splittext.go b/splittext.go
new file mode 100644
index 0000000..3902199
--- /dev/null
+++ b/splittext.go
@@ -0,0 +1,54 @@
+package gofpdf
+
+import (
+	"math"
+	//	"strings"
+	"unicode"
+)
+
+// SplitText splits UTF-8 encoded text into several lines using the current
+// font. Each line has its length limited to a maximum width given by w. This
+// function can be used to determine the total height of wrapped text for
+// vertical placement purposes.
+func (f *Fpdf) SplitText(txt string, w float64) (lines []string) {
+	cw := f.currentFont.Cw
+	wmax := int(math.Ceil((w - 2*f.cMargin) * 1000 / f.fontSize))
+	s := []rune(txt) // Return slice of UTF-8 runes
+	nb := len(s)
+	for nb > 0 && s[nb-1] == '\n' {
+		nb--
+	}
+	s = s[0:nb]
+	sep := -1
+	i := 0
+	j := 0
+	l := 0
+	for i < nb {
+		c := s[i]
+		l += cw[c]
+		if unicode.IsSpace(c) {
+			// if c == ' ' || c == '\t' || c == '\n' {
+			sep = i
+		}
+		if c == '\n' || l > wmax {
+			if sep == -1 {
+				if i == j {
+					i++
+				}
+				sep = i
+			} else {
+				i = sep + 1
+			}
+			lines = append(lines, string(s[j:sep]))
+			sep = -1
+			j = i
+			l = 0
+		} else {
+			i++
+		}
+	}
+	if i != j {
+		lines = append(lines, string(s[j:i]))
+	}
+	return lines
+}