Support subscripted and superscripted text with new SubWrite method

2 files changed, 83 insertions, 0 deletions

diff --git a/fpdf_test.go b/fpdf_test.go
index 2fbca9c..86fae86 100644
--- a/fpdf_test.go
+++ b/fpdf_test.go
@@ -2325,3 +2325,53 @@ func ExampleFpdf_SetPageBox() {
 	// Output:
 	// Successfully generated pdf/Fpdf_PageBox.pdf
 }
+
+// ExampleFpdf_SubWrite demonstrates subscripted and superscripted text
+// Adapted from http://www.fpdf.org/en/script/script61.php
+func ExampleFpdf_SubWrite() {
+
+	const (
+		fontSize = 12
+		halfX    = 105
+	)
+
+	pdf := gofpdf.New("P", "mm", "A4", "") // 210mm x 297mm
+	pdf.AddPage()
+	pdf.SetFont("Arial", "", fontSize)
+	_, lineHt := pdf.GetFontSize()
+
+	pdf.Write(lineHt, "Hello World!")
+	pdf.SetX(halfX)
+	pdf.Write(lineHt, "This is standard text.\n")
+	pdf.Ln(lineHt * 2)
+
+	pdf.SubWrite(10, "H", 33, 0, 0, "")
+	pdf.Write(10, "ello World!")
+	pdf.SetX(halfX)
+	pdf.Write(10, "This is text with a capital first letter.\n")
+	pdf.Ln(lineHt * 2)
+
+	pdf.SubWrite(lineHt, "Y", 6, 0, 0, "")
+	pdf.Write(lineHt, "ou can also begin the sentence with a small letter. And word wrap also works if the line is too long, like this one is.")
+	pdf.SetX(halfX)
+	pdf.Write(lineHt, "This is text with a small first letter.\n")
+	pdf.Ln(lineHt * 2)
+
+	pdf.Write(lineHt, "The world has a lot of km")
+	pdf.SubWrite(lineHt, "2", 6, 4, 0, "")
+	pdf.SetX(halfX)
+	pdf.Write(lineHt, "This is text with a superscripted letter.\n")
+	pdf.Ln(lineHt * 2)
+
+	pdf.Write(lineHt, "The world has a lot of H")
+	pdf.SubWrite(lineHt, "2", 6, -3, 0, "")
+	pdf.Write(lineHt, "O")
+	pdf.SetX(halfX)
+	pdf.Write(lineHt, "This is text with a subscripted letter.\n")
+
+	fileStr := example.Filename("Fpdf_SubWrite")
+	err := pdf.OutputFileAndClose(fileStr)
+	example.Summary(err, fileStr)
+	// Output:
+	// Successfully generated pdf/Fpdf_SubWrite.pdf
+}
diff --git a/subwrite.go b/subwrite.go
new file mode 100644
index 0000000..dbeee5b
--- /dev/null
+++ b/subwrite.go
@@ -0,0 +1,33 @@
+package gofpdf
+
+// Adapted from http://www.fpdf.org/en/script/script61.php by Wirus and released with the FPDF license.
+
+// SubWrite prints text from the current position in the same way as Write().
+// ht is the line height in the unit of measure specified in New(). str
+// specifies the text to write. subFontSize is the size of the font in points.
+// subOffset is the vertical offset of the text in points; a positive value
+// indicates a superscript, a negative value indicates a subscript. link is the
+// identifier returned by AddLink() or 0 for no internal link. linkStr is a
+// target URL or empty for no external link. A non--zero value for link takes
+// precedence over linkStr.
+func (f *Fpdf) SubWrite(ht float64, str string, subFontSize, subOffset float64, link int, linkStr string) {
+	if f.err != nil {
+		return
+	}
+	// resize font
+	subFontSizeOld := f.fontSizePt
+	f.SetFontSize(subFontSize)
+	// reposition y
+	subOffset = (((subFontSize - subFontSizeOld) / f.k) * 0.3) + (subOffset / f.k)
+	subX := f.x
+	subY := f.y
+	f.SetXY(subX, subY-subOffset)
+	//Output text
+	f.write(ht, str, link, linkStr)
+	// restore y position
+	subX = f.x
+	subY = f.y
+	f.SetXY(subX, subY+subOffset)
+	// restore font size
+	f.SetFontSize(subFontSizeOld)
+}