diff --git a/ccutil/unichar.cpp b/ccutil/unichar.cpp
index b75dff6d..0ceced13 100644
--- a/ccutil/unichar.cpp
+++ b/ccutil/unichar.cpp
@@ -206,12 +206,20 @@ UNICHAR::const_iterator UNICHAR::end(const char* utf8_str, const int len) {
 }
 
 // Converts a utf-8 string to a vector of unicodes.
-void UNICHAR::UTF8ToUnicode(const char* utf8_str,
+// Returns false if the input contains invalid UTF-8, and replaces
+// the rest of the string with a single space.
+bool UNICHAR::UTF8ToUnicode(const char* utf8_str,
                             GenericVector<int>* unicodes) {
   const int utf8_length = strlen(utf8_str);
   const_iterator end_it(end(utf8_str, utf8_length));
   for (const_iterator it(begin(utf8_str, utf8_length)); it != end_it; ++it) {
-    unicodes->push_back(*it);
+    if (it.is_legal()) {
+      unicodes->push_back(*it);
+    } else {
+      unicodes->push_back(' ');
+      return false;
+    }
   }
+  return true;
 }
 
diff --git a/ccutil/unichar.h b/ccutil/unichar.h
index 7e5cd9fb..b2a1e013 100644
--- a/ccutil/unichar.h
+++ b/ccutil/unichar.h
@@ -151,7 +151,9 @@ class UNICHAR {
   static const_iterator end(const char* utf8_str, const int byte_length);
 
   // Converts a utf-8 string to a vector of unicodes.
-  static void UTF8ToUnicode(const char* utf8_str, GenericVector<int>* unicodes);
+  // Returns false if the input contains invalid UTF-8, and replaces
+  // the rest of the string with a single space.
+  static bool UTF8ToUnicode(const char* utf8_str, GenericVector<int>* unicodes);
 
  private:
   // A UTF-8 representation of 1 or more Unicode characters.
diff --git a/training/boxchar.cpp b/training/boxchar.cpp
index b3b71732..276d8af6 100644
--- a/training/boxchar.cpp
+++ b/training/boxchar.cpp
@@ -23,9 +23,18 @@
 #include "boxchar.h"
 
 #include <stddef.h>
+#include <algorithm>
 
 #include "fileio.h"
+#include "genericvector.h"
 #include "ndminx.h"
+#include "normstrngs.h"
+#include "tprintf.h"
+#include "unicharset.h"
+#include "unicode/uchar.h"  // from libicu
+
+// Absolute Ratio of dx:dy or dy:dx to be a newline.
+const int kMinNewlineRatio = 5;
 
 namespace tesseract {
 
@@ -33,17 +42,14 @@ BoxChar::BoxChar(const char* utf8_str, int len) : ch_(utf8_str, len) {
   box_ = NULL;
 }
 
-BoxChar::~BoxChar() {
-  boxDestroy(&box_);
-}
+BoxChar::~BoxChar() { boxDestroy(&box_); }
 
 void BoxChar::AddBox(int x, int y, int width, int height) {
   box_ = boxCreate(x, y, width, height);
 }
 
 /* static */
-void BoxChar::TranslateBoxes(int xshift, int yshift,
-                             vector<BoxChar*>* boxes) {
+void BoxChar::TranslateBoxes(int xshift, int yshift, vector<BoxChar*>* boxes) {
   for (int i = 0; i < boxes->size(); ++i) {
     BOX* box = (*boxes)[i]->box_;
     if (box != NULL) {
@@ -53,15 +59,218 @@ void BoxChar::TranslateBoxes(int xshift, int yshift,
   }
 }
 
+// Prepares for writing the boxes to a file by inserting newlines, spaces,
+// and re-ordering so the boxes are strictly left-to-right.
+/* static */
+void BoxChar::PrepareToWrite(vector<BoxChar*>* boxes) {
+  bool rtl_rules = ContainsMostlyRTL(*boxes);
+  bool vertical_rules = MostlyVertical(*boxes);
+  InsertNewlines(rtl_rules, vertical_rules, boxes);
+  InsertSpaces(rtl_rules, vertical_rules, boxes);
+  for (int i = 0; i < boxes->size(); ++i) {
+    if ((*boxes)[i]->box_ == NULL) tprintf("Null box at index %d\n", i);
+  }
+  if (rtl_rules) {
+    ReorderRTLText(boxes);
+  }
+  tprintf("Rtl = %d ,vertical=%d\n", rtl_rules, vertical_rules);
+}
+
+// Inserts newline (tab) characters into the vector at newline positions.
+/* static */
+void BoxChar::InsertNewlines(bool rtl_rules, bool vertical_rules,
+                             vector<BoxChar*>* boxes) {
+  int prev_i = -1;
+  int max_shift = 0;
+  for (int i = 0; i < boxes->size(); ++i) {
+    Box* box = (*boxes)[i]->box_;
+    if (box == NULL) {
+      if (prev_i < 0 || prev_i < i - 1 || i + 1 == boxes->size()) {
+        // Erase null boxes at the start of a line and after another null box.
+        do {
+          delete (*boxes)[i];
+          boxes->erase(boxes->begin() + i);
+          --i;
+        } while (i >= 0 && i + 1 == boxes->size() && (*boxes)[i]->box_ == NULL);
+      }
+      continue;
+    }
+    if (prev_i >= 0) {
+      Box* prev_box = (*boxes)[prev_i]->box_;
+      int shift = box->x - prev_box->x;
+      if (vertical_rules) {
+        shift = box->y - prev_box->y;
+      } else if (rtl_rules) {
+        shift = -shift;
+      }
+      if (-shift > max_shift) {
+        // This is a newline.
+        int width = prev_box->w;
+        int height = prev_box->h;
+        int x = prev_box->x + width;
+        int y = prev_box->y;
+        if (vertical_rules) {
+          x = prev_box->x;
+          y = prev_box->y + height;
+        } else if (rtl_rules) {
+          x = prev_box->x - width;
+          if (x < 0) {
+            tprintf("prev x = %d, width=%d\n", prev_box->x, width);
+            x = 0;
+          }
+        }
+        if (prev_i == i - 1) {
+          // New character needed.
+          BoxChar* new_box = new BoxChar("\t", 1);
+          new_box->AddBox(x, y, width, height);
+          new_box->page_ = (*boxes)[i]->page_;
+          boxes->insert(boxes->begin() + i, new_box);
+          ++i;
+        } else {
+          (*boxes)[i - 1]->AddBox(x, y, width, height);
+          (*boxes)[i - 1]->ch_ = "\t";
+        }
+        max_shift = 0;
+      } else if (shift > max_shift) {
+        max_shift = shift;
+      }
+    }
+    prev_i = i;
+  }
+}
+
+// Converts NULL boxes to space characters, with appropriate bounding boxes.
+/* static */
+void BoxChar::InsertSpaces(bool rtl_rules, bool vertical_rules,
+                           vector<BoxChar*>* boxes) {
+  // After InsertNewlines, any remaining null boxes are not newlines, and are
+  // singletons, so add a box to each remaining null box.
+  for (int i = 1; i + 1 < boxes->size(); ++i) {
+    Box* box = (*boxes)[i]->box_;
+    if (box == NULL) {
+      Box* prev = (*boxes)[i - 1]->box_;
+      Box* next = (*boxes)[i + 1]->box_;
+      ASSERT_HOST(prev != NULL && next != NULL);
+      int top = MIN(prev->y, next->y);
+      int bottom = MAX(prev->y + prev->h, next->y + next->h);
+      int left = prev->x + prev->w;
+      int right = next->x;
+      if (vertical_rules) {
+        top = prev->y + prev->h;
+        bottom = next->y;
+        left = MIN(prev->x, next->x);
+        right = MAX(prev->x + prev->w, next->x + next->w);
+      } else if (rtl_rules) {
+        // With RTL we have to account for BiDi.
+        // Right becomes the min left of all prior boxes back to the first
+        // space or newline.
+        right = prev->x;
+        left = next->x + next->w;
+        for (int j = i - 2;
+             j >= 0 && (*boxes)[j]->ch_ != " " && (*boxes)[j]->ch_ != "\t";
+             --j) {
+          prev = (*boxes)[j]->box_;
+          ASSERT_HOST(prev != NULL);
+          if (prev->x < right) {
+            right = prev->x;
+          }
+        }
+        // Left becomes the max right of all next boxes foward to the first
+        // space or newline.
+        for (int j = i + 2; j < boxes->size() && (*boxes)[j]->box_ != NULL &&
+                                (*boxes)[j]->ch_ != "\t";
+             ++j) {
+          next = (*boxes)[j]->box_;
+          if (next->x + next->w > left) {
+            left = next->x + next->w;
+          }
+        }
+      }
+      // Italic and stylized characters can produce negative spaces, which
+      // Leptonica doesn't like, so clip to a positive size.
+      if (right <= left) right = left + 1;
+      if (bottom <= top) bottom = top + 1;
+      (*boxes)[i]->AddBox(left, top, right - left, bottom - top);
+      (*boxes)[i]->ch_ = " ";
+    }
+  }
+}
+
+// Reorders text in a right-to-left script in left-to-right order.
+/* static */
+void BoxChar::ReorderRTLText(vector<BoxChar*>* boxes) {
+  // After adding newlines and spaces, this task is simply a matter of sorting
+  // by left each group of boxes between newlines.
+  BoxCharPtrSort sorter;
+  int end = 0;
+  for (int start = 0; start < boxes->size(); start = end + 1) {
+    end = start + 1;
+    while (end < boxes->size() && (*boxes)[end]->ch_ != "\t") ++end;
+    sort(boxes->begin() + start, boxes->begin() + end, sorter);
+  }
+}
+
+// Returns true if the vector contains mostly RTL characters.
+/* static */
+bool BoxChar::ContainsMostlyRTL(const vector<BoxChar*>& boxes) {
+  int num_rtl = 0, num_ltr = 0;
+  for (int i = 0; i < boxes.size(); ++i) {
+    // Convert the unichar to UTF32 representation
+    GenericVector<char32> uni_vector;
+    if (!UNICHAR::UTF8ToUnicode(boxes[i]->ch_.c_str(), &uni_vector)) {
+      tprintf("Illegal utf8 in boxchar %d string:%s = ", i,
+              boxes[i]->ch_.c_str());
+      for (int c = 0; c < boxes[i]->ch_.size(); ++c) {
+        tprintf(" 0x%x", boxes[i]->ch_[c]);
+      }
+      tprintf("\n");
+      continue;
+    }
+    for (int j = 0; j < uni_vector.size(); ++j) {
+      UCharDirection dir = u_charDirection(uni_vector[j]);
+      if (dir == U_RIGHT_TO_LEFT || dir == U_RIGHT_TO_LEFT_ARABIC ||
+          dir == U_ARABIC_NUMBER) {
+        ++num_rtl;
+      } else {
+        ++num_ltr;
+      }
+    }
+  }
+  return num_rtl > num_ltr;
+}
+
+// Returns true if the text is mostly laid out vertically.
+/* static */
+bool BoxChar::MostlyVertical(const vector<BoxChar*>& boxes) {
+  inT64 total_dx = 0, total_dy = 0;
+  for (int i = 1; i < boxes.size(); ++i) {
+    if (boxes[i - 1]->box_ != NULL && boxes[i]->box_ != NULL &&
+        boxes[i - 1]->page_ == boxes[i]->page_) {
+      int dx = boxes[i]->box_->x - boxes[i - 1]->box_->x;
+      int dy = boxes[i]->box_->y - boxes[i - 1]->box_->y;
+      if (abs(dx) > abs(dy) * kMinNewlineRatio ||
+          abs(dy) > abs(dx) * kMinNewlineRatio) {
+        total_dx += dx * dx;
+        total_dy += dy * dy;
+      }
+    }
+  }
+  return total_dy > total_dx;
+}
+
+// Returns the total length of all the strings in the boxes.
+/* static */
+int BoxChar::TotalByteLength(const vector<BoxChar*>& boxes) {
+  int total_length = 0;
+  for (int i = 0; i < boxes.size(); ++i) total_length += boxes[i]->ch_.size();
+  return total_length;
+}
+
 // Rotate the boxes in [start_box, end_box) by the given rotation.
 // The rotation is in radians clockwise about the given center.
 /* static */
-void BoxChar::RotateBoxes(float rotation,
-                          int xcenter,
-                          int ycenter,
-                          int start_box,
-                          int end_box,
-                          vector<BoxChar*>* boxes) {
+void BoxChar::RotateBoxes(float rotation, int xcenter, int ycenter,
+                          int start_box, int end_box, vector<BoxChar*>* boxes) {
   Boxa* orig = boxaCreate(0);
   for (int i = start_box; i < end_box; ++i) {
     BOX* box = (*boxes)[i]->box_;
@@ -79,16 +288,6 @@ void BoxChar::RotateBoxes(float rotation,
 }
 
 const int kMaxLineLength = 1024;
-// Helper appends a tab box to the string to indicate a newline. We can't use
-// an actual newline as the file format is line-based text.
-static void AppendTabBox(const Box* box, int height, int page, string* output) {
-  char buffer[kMaxLineLength];
-  int nbytes = snprintf(buffer, kMaxLineLength, "\t %d %d %d %d %d\n",
-                        box->x + box->w, height - box->y - box->h,
-                        box->x + box->w + 10, height - box->y, page);
-  output->append(buffer, nbytes);
-}
-
 /* static */
 void BoxChar::WriteTesseractBoxFile(const string& filename, int height,
                                     const vector<BoxChar*>& boxes) {
@@ -96,43 +295,15 @@ void BoxChar::WriteTesseractBoxFile(const string& filename, int height,
   char buffer[kMaxLineLength];
   for (int i = 0; i < boxes.size(); ++i) {
     const Box* box = boxes[i]->box_;
-    if (box != NULL) {
-      if (i > 0 && boxes[i - 1]->box_ != NULL &&
-          boxes[i - 1]->page_ == boxes[i]->page_ &&
-          box->x + box->w < boxes[i - 1]->box_->x) {
-        // We are on a newline. Output a tab character to indicate the newline.
-        AppendTabBox(boxes[i - 1]->box_, height, boxes[i]->page_, &output);
-      }
-      int nbytes = snprintf(buffer, kMaxLineLength,
-                            "%s %d %d %d %d %d\n",
-                            boxes[i]->ch_.c_str(),
-                            box->x, height - box->y - box->h,
-                            box->x + box->w, height - box->y,
-                            boxes[i]->page_);
-      output.append(buffer, nbytes);
-    } else if (i > 0 && boxes[i - 1]->box_ != NULL) {
-      int j = i + 1;
-      // Find the next non-null box, as there may be multiple spaces.
-      while (j < boxes.size() && boxes[j]->box_ == NULL) ++j;
-      if (j < boxes.size() && boxes[i - 1]->page_ == boxes[j]->page_) {
-        const Box* prev = boxes[i - 1]->box_;
-        const Box* next = boxes[j]->box_;
-        if (next->x + next->w < prev->x) {
-          // We are on a newline. Output a tab character to indicate it.
-          AppendTabBox(prev, height, boxes[j]->page_, &output);
-        } else {
-          // Space between words.
-          int nbytes = snprintf(buffer, kMaxLineLength,
-                                "  %d %d %d %d %d\n",
-                                prev->x + prev->w,
-                                height - MAX(prev->y + prev->h,
-                                             next->y + next->h),
-                                next->x, height - MIN(prev->y, next->y),
-                                boxes[i - 1]->page_);
-          output.append(buffer, nbytes);
-        }
-      }
+    if (box == NULL) {
+      tprintf("Error: Call PrepareToWrite before WriteTesseractBoxFile!!\n");
+      return;
     }
+    int nbytes =
+        snprintf(buffer, kMaxLineLength, "%s %d %d %d %d %d\n",
+                 boxes[i]->ch_.c_str(), box->x, height - box->y - box->h,
+                 box->x + box->w, height - box->y, boxes[i]->page_);
+    output.append(buffer, nbytes);
   }
   File::WriteStringToFileOrDie(output, filename);
 }
diff --git a/training/boxchar.h b/training/boxchar.h
index bcb102ce..27b568a1 100644
--- a/training/boxchar.h
+++ b/training/boxchar.h
@@ -57,9 +57,36 @@ class BoxChar {
   string* mutable_ch() { return &ch_; }
   Box* mutable_box()   { return box_; }
 
+  // Sort function for sorting by left edge of box. Note that this will not
+  // work properly until after InsertNewlines and InsertSpaces.
+  bool operator<(const BoxChar& other) const {
+    if (box_ == NULL) return true;
+    if (other.box_ == NULL) return false;
+    return box_->x < other.box_->x;
+  }
+
   static void TranslateBoxes(int xshift, int yshift,
                              vector<BoxChar*>* boxes);
 
+  // Prepares for writing the boxes to a file by inserting newlines, spaces,
+  // and re-ordering so the boxes are strictly left-to-right.
+  static void PrepareToWrite(vector<BoxChar*>* boxes);
+  // Inserts newline (tab) characters into the vector at newline positions.
+  static void InsertNewlines(bool rtl_rules, bool vertical_rules,
+                             vector<BoxChar*>* boxes);
+  // Converts NULL boxes to space characters, with appropriate bounding boxes.
+  static void InsertSpaces(bool rtl_rules, bool vertical_rules,
+                           vector<BoxChar*>* boxes);
+  // Reorders text in a right-to-left script in left-to-right order.
+  static void ReorderRTLText(vector<BoxChar*>* boxes);
+  // Returns true if the vector contains mostly RTL characters.
+  static bool ContainsMostlyRTL(const vector<BoxChar*>& boxes);
+  // Returns true if the text is mostly laid out vertically.
+  static bool MostlyVertical(const vector<BoxChar*>& boxes);
+
+  // Returns the total length of all the strings in the boxes.
+  static int TotalByteLength(const vector<BoxChar*>& boxes);
+
   // Rotate the vector of boxes between start and end by the given rotation.
   // The rotation is in radians clockwise about the given center.
   static void RotateBoxes(float rotation,
@@ -79,6 +106,14 @@ class BoxChar {
   Box* box_;
   int page_;
 };
+
+// Sort predicate to sort a vector of BoxChar*.
+struct BoxCharPtrSort {
+  bool operator()(const BoxChar* box1, const BoxChar* box2) const {
+    return *box1 < *box2;
+  }
+};
+
 }  // namespace tesseract
 
 #endif  // TESSERACT_TRAINING_BOXCHAR_H_
diff --git a/training/stringrenderer.cpp b/training/stringrenderer.cpp
index a448b92e..8bef6699 100644
--- a/training/stringrenderer.cpp
+++ b/training/stringrenderer.cpp
@@ -330,7 +330,8 @@ void StringRenderer::ClearBoxes() {
   boxaDestroy(&page_boxes_);
 }
 
-void StringRenderer::WriteAllBoxes(const string& filename) const {
+void StringRenderer::WriteAllBoxes(const string& filename) {
+  BoxChar::PrepareToWrite(&boxchars_);
   BoxChar::WriteTesseractBoxFile(filename, page_height_, boxchars_);
 }
 
diff --git a/training/stringrenderer.h b/training/stringrenderer.h
index 1fd62d4d..d96e572e 100644
--- a/training/stringrenderer.h
+++ b/training/stringrenderer.h
@@ -148,7 +148,7 @@ class StringRenderer {
   void RotatePageBoxes(float rotation);
   // Delete all boxes.
   void ClearBoxes();
-  void WriteAllBoxes(const string& filename) const;
+  void WriteAllBoxes(const string& filename);
   // Removes space-delimited words from the string that are not renderable by
   // the current font and returns the count of such words.
   int StripUnrenderableWords(string* utf8_text) const;