From 5b0eaf3f3adeb1ae38f049fb795d82015aa423b3 Mon Sep 17 00:00:00 2001
From: Denys Smirnov <denys@sourced.tech>
Date: Thu, 29 Nov 2018 02:56:26 +0200
Subject: [PATCH] creator: make output stable when using custom fonts; fixes
 #232

---
 pdf/creator/creator_test.go | 35 +++++++++++++++++++++++++++++++++++
 pdf/model/font_composite.go |  5 +++++
 2 files changed, 40 insertions(+)

diff --git a/pdf/creator/creator_test.go b/pdf/creator/creator_test.go
index 418d1371..0bd42e6f 100644
--- a/pdf/creator/creator_test.go
+++ b/pdf/creator/creator_test.go
@@ -11,6 +11,8 @@ package creator
 
 import (
 	"bytes"
+	"crypto/md5"
+	"encoding/hex"
 	"fmt"
 	goimage "image"
 	"io/ioutil"
@@ -2932,3 +2934,36 @@ func TestAllOptimizations(t *testing.T) {
 		t.Errorf("Optimization failed: size not changed %d vs %d", fileInfo.Size(), fileInfoOptimized.Size())
 	}
 }
+
+// Tests that creator's output is predictable and returns exactly the same file given the same input.
+func TestCreatorStable(t *testing.T) {
+	writePDF := func() string {
+		creator := New()
+
+		font, err := model.NewCompositePdfFontFromTTFFile(testWts11TTFFile)
+		if err != nil {
+			t.Fatalf("Fail: %v\n", err)
+		}
+
+		p := creator.NewParagraph("你好")
+		p.SetFont(font)
+
+		err = creator.Draw(p)
+		if err != nil {
+			t.Fatalf("Fail: %v\n", err)
+		}
+
+		h := md5.New()
+		err = creator.Write(h)
+		if err != nil {
+			t.Fatalf("Fail: %v\n", err)
+		}
+		return hex.EncodeToString(h.Sum(nil))
+	}
+
+	h1 := writePDF()
+	h2 := writePDF()
+	if h1 != h2 {
+		t.Fatal("output is not stable")
+	}
+}
diff --git a/pdf/model/font_composite.go b/pdf/model/font_composite.go
index 968ebc30..4f132c80 100644
--- a/pdf/model/font_composite.go
+++ b/pdf/model/font_composite.go
@@ -8,6 +8,7 @@ package model
 import (
 	"errors"
 	"io/ioutil"
+	"sort"
 
 	"github.com/unidoc/unidoc/common"
 	"github.com/unidoc/unidoc/pdf/core"
@@ -412,6 +413,10 @@ func NewCompositePdfFontFromTTFFile(filePath string) (*PdfFont, error) {
 	for r := range ttf.Chars {
 		runes = append(runes, r)
 	}
+	// make sure runes are sorted so PDF output is stable
+	sort.Slice(runes, func(i, j int) bool {
+		return runes[i] < runes[j]
+	})
 
 	k := 1000.0 / float64(ttf.UnitsPerEm)