--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mupdf-source/thirdparty/tesseract/src/textord/alignedblob.cpp	Mon Sep 15 11:43:07 2025 +0200
@@ -0,0 +1,545 @@
+///////////////////////////////////////////////////////////////////////
+// File:        alignedblob.cpp
+// Description: Subclass of BBGrid to find vertically aligned blobs.
+// Author:      Ray Smith
+//
+// (C) Copyright 2008, Google Inc.
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+///////////////////////////////////////////////////////////////////////
+
+#ifdef HAVE_CONFIG_H
+#  include "config_auto.h"
+#endif
+
+#include "alignedblob.h"
+
+#include <algorithm>
+
+namespace tesseract {
+
+INT_VAR(textord_debug_tabfind, 0, "Debug tab finding");
+INT_VAR(textord_debug_bugs, 0, "Turn on output related to bugs in tab finding");
+static INT_VAR(textord_testregion_left, -1,
+               "Left edge of debug reporting rectangle in Leptonica coords "
+               "(bottom=0/top=height), with horizontal lines x/y-flipped");
+static INT_VAR(textord_testregion_top, INT32_MAX,
+               "Top edge of debug reporting rectangle in Leptonica coords "
+               "(bottom=0/top=height), with horizontal lines x/y-flipped");
+static INT_VAR(textord_testregion_right, INT32_MAX,
+               "Right edge of debug rectangle in Leptonica coords "
+               "(bottom=0/top=height), with horizontal lines x/y-flipped");
+static INT_VAR(textord_testregion_bottom, -1,
+               "Bottom edge of debug rectangle in Leptonica coords "
+               "(bottom=0/top=height), with horizontal lines x/y-flipped");
+BOOL_VAR(textord_debug_printable, false, "Make debug windows printable");
+
+// Fraction of resolution used as alignment tolerance for aligned tabs.
+const double kAlignedFraction = 0.03125;
+// Fraction of resolution used as alignment tolerance for ragged tabs.
+const double kRaggedFraction = 2.5;
+// Fraction of height used as a minimum gutter gap for aligned blobs.
+const double kAlignedGapFraction = 0.75;
+// Fraction of height used as a minimum gutter gap for ragged tabs.
+const double kRaggedGapFraction = 1.0;
+// Constant number of pixels used as alignment tolerance for line finding.
+const int kVLineAlignment = 3;
+// Constant number of pixels used as gutter gap tolerance for line finding.
+const int kVLineGutter = 1;
+// Constant number of pixels used as the search size for line finding.
+const int kVLineSearchSize = 150;
+// Min number of points to accept for a ragged tab stop.
+const int kMinRaggedTabs = 5;
+// Min number of points to accept for an aligned tab stop.
+const int kMinAlignedTabs = 4;
+// Constant number of pixels minimum height of a vertical line.
+const int kVLineMinLength = 300;
+// Minimum gradient for a vertical tab vector. Used to prune away junk
+// tab vectors with what would be a ridiculously large skew angle.
+// Value corresponds to tan(90 - max allowed skew angle)
+const double kMinTabGradient = 4.0;
+// Tolerance to skew on top of current estimate of skew. Divide x or y length
+// by kMaxSkewFactor to get the y or x skew distance.
+// If the angle is small, the angle in degrees is roughly 60/kMaxSkewFactor.
+const int kMaxSkewFactor = 15;
+
+// Constructor to set the parameters for finding aligned and ragged tabs.
+// Vertical_x and vertical_y are the current estimates of the true vertical
+// direction (up) in the image. Height is the height of the starter blob.
+// v_gap_multiple is the multiple of height that will be used as a limit
+// on vertical gap before giving up and calling the line ended.
+// resolution is the original image resolution, and align0 indicates the
+// type of tab stop to be found.
+AlignedBlobParams::AlignedBlobParams(int vertical_x, int vertical_y, int height, int v_gap_multiple,
+                                     int min_gutter_width, int resolution, TabAlignment align0)
+    : right_tab(align0 == TA_RIGHT_RAGGED || align0 == TA_RIGHT_ALIGNED)
+    , ragged(align0 == TA_LEFT_RAGGED || align0 == TA_RIGHT_RAGGED)
+    , alignment(align0)
+    , confirmed_type(TT_CONFIRMED)
+    , min_length(0) {
+  // Set the tolerances according to the type of line sought.
+  // For tab search, these are based on the image resolution for most, or
+  // the height of the starting blob for the maximum vertical gap.
+  max_v_gap = height * v_gap_multiple;
+  if (ragged) {
+    // In the case of a ragged edge, we are much more generous with the
+    // inside alignment fraction, but also require a much bigger gutter.
+    gutter_fraction = kRaggedGapFraction;
+    if (alignment == TA_RIGHT_RAGGED) {
+      l_align_tolerance = static_cast<int>(resolution * kRaggedFraction + 0.5);
+      r_align_tolerance = static_cast<int>(resolution * kAlignedFraction + 0.5);
+    } else {
+      l_align_tolerance = static_cast<int>(resolution * kAlignedFraction + 0.5);
+      r_align_tolerance = static_cast<int>(resolution * kRaggedFraction + 0.5);
+    }
+    min_points = kMinRaggedTabs;
+  } else {
+    gutter_fraction = kAlignedGapFraction;
+    l_align_tolerance = static_cast<int>(resolution * kAlignedFraction + 0.5);
+    r_align_tolerance = static_cast<int>(resolution * kAlignedFraction + 0.5);
+    min_points = kMinAlignedTabs;
+  }
+  min_gutter = static_cast<int>(height * gutter_fraction + 0.5);
+  if (min_gutter < min_gutter_width) {
+    min_gutter = min_gutter_width;
+  }
+  // Fit the vertical vector into an ICOORD, which is 16 bit.
+  set_vertical(vertical_x, vertical_y);
+}
+
+// Constructor to set the parameters for finding vertical lines.
+// Vertical_x and vertical_y are the current estimates of the true vertical
+// direction (up) in the image. Width is the width of the starter blob.
+AlignedBlobParams::AlignedBlobParams(int vertical_x, int vertical_y, int width)
+    : gutter_fraction(0.0)
+    , right_tab(false)
+    , ragged(false)
+    , alignment(TA_SEPARATOR)
+    , confirmed_type(TT_VLINE)
+    , max_v_gap(kVLineSearchSize)
+    , min_gutter(kVLineGutter)
+    , min_points(1)
+    , min_length(kVLineMinLength) {
+  // Compute threshold for left and right alignment.
+  l_align_tolerance = std::max(kVLineAlignment, width);
+  r_align_tolerance = std::max(kVLineAlignment, width);
+
+  // Fit the vertical vector into an ICOORD, which is 16 bit.
+  set_vertical(vertical_x, vertical_y);
+}
+
+// Fit the vertical vector into an ICOORD, which is 16 bit.
+void AlignedBlobParams::set_vertical(int vertical_x, int vertical_y) {
+  int factor = 1;
+  if (vertical_y > INT16_MAX) {
+    factor = vertical_y / INT16_MAX + 1;
+  }
+  vertical.set_x(vertical_x / factor);
+  vertical.set_y(vertical_y / factor);
+}
+
+AlignedBlob::AlignedBlob(int gridsize, const ICOORD &bleft, const ICOORD &tright)
+    : BlobGrid(gridsize, bleft, tright) {}
+
+// Return true if the given coordinates are within the test rectangle
+// and the debug level is at least the given detail level.
+bool AlignedBlob::WithinTestRegion(int detail_level, int x, int y) {
+  if (textord_debug_tabfind < detail_level) {
+    return false;
+  }
+  return x >= textord_testregion_left && x <= textord_testregion_right &&
+         y <= textord_testregion_top && y >= textord_testregion_bottom;
+}
+
+#ifndef GRAPHICS_DISABLED
+
+// Display the tab codes of the BLOBNBOXes in this grid.
+ScrollView *AlignedBlob::DisplayTabs(const char *window_name, ScrollView *tab_win) {
+  if (tab_win == nullptr) {
+    tab_win = MakeWindow(0, 50, window_name);
+  }
+  // For every tab in the grid, display it.
+  BlobGridSearch gsearch(this);
+  gsearch.StartFullSearch();
+  BLOBNBOX *bbox;
+  while ((bbox = gsearch.NextFullSearch()) != nullptr) {
+    const TBOX &box = bbox->bounding_box();
+    int left_x = box.left();
+    int right_x = box.right();
+    int top_y = box.top();
+    int bottom_y = box.bottom();
+    TabType tabtype = bbox->left_tab_type();
+    if (tabtype != TT_NONE) {
+      if (tabtype == TT_MAYBE_ALIGNED) {
+        tab_win->Pen(ScrollView::BLUE);
+      } else if (tabtype == TT_MAYBE_RAGGED) {
+        tab_win->Pen(ScrollView::YELLOW);
+      } else if (tabtype == TT_CONFIRMED) {
+        tab_win->Pen(ScrollView::GREEN);
+      } else {
+        tab_win->Pen(ScrollView::GREY);
+      }
+      tab_win->Line(left_x, top_y, left_x, bottom_y);
+    }
+    tabtype = bbox->right_tab_type();
+    if (tabtype != TT_NONE) {
+      if (tabtype == TT_MAYBE_ALIGNED) {
+        tab_win->Pen(ScrollView::MAGENTA);
+      } else if (tabtype == TT_MAYBE_RAGGED) {
+        tab_win->Pen(ScrollView::ORANGE);
+      } else if (tabtype == TT_CONFIRMED) {
+        tab_win->Pen(ScrollView::RED);
+      } else {
+        tab_win->Pen(ScrollView::GREY);
+      }
+      tab_win->Line(right_x, top_y, right_x, bottom_y);
+    }
+  }
+  tab_win->Update();
+  return tab_win;
+}
+
+#endif // !GRAPHICS_DISABLED
+
+// Helper returns true if the total number of line_crossings of all the blobs
+// in the list is at least 2.
+static bool AtLeast2LineCrossings(BLOBNBOX_CLIST *blobs) {
+  BLOBNBOX_C_IT it(blobs);
+  int total_crossings = 0;
+  for (it.mark_cycle_pt(); !it.cycled_list(); it.forward()) {
+    total_crossings += it.data()->line_crossings();
+  }
+  return total_crossings >= 2;
+}
+
+// Destructor.
+// It is defined here, so the compiler can create a single vtable
+// instead of weak vtables in every compilation unit.
+AlignedBlob::~AlignedBlob() = default;
+
+// Finds a vector corresponding to a set of vertically aligned blob edges
+// running through the given box. The type of vector returned and the
+// search parameters are determined by the AlignedBlobParams.
+// vertical_x and y are updated with an estimate of the real
+// vertical direction. (skew finding.)
+// Returns nullptr if no decent vector can be found.
+TabVector *AlignedBlob::FindVerticalAlignment(AlignedBlobParams align_params, BLOBNBOX *bbox,
+                                              int *vertical_x, int *vertical_y) {
+  int ext_start_y, ext_end_y;
+  BLOBNBOX_CLIST good_points;
+  // Search up and then down from the starting bbox.
+  TBOX box = bbox->bounding_box();
+  bool debug = WithinTestRegion(2, box.left(), box.bottom());
+  int pt_count = AlignTabs(align_params, false, bbox, &good_points, &ext_end_y);
+  pt_count += AlignTabs(align_params, true, bbox, &good_points, &ext_start_y);
+  BLOBNBOX_C_IT it(&good_points);
+  it.move_to_last();
+  box = it.data()->bounding_box();
+  int end_y = box.top();
+  int end_x = align_params.right_tab ? box.right() : box.left();
+  it.move_to_first();
+  box = it.data()->bounding_box();
+  int start_x = align_params.right_tab ? box.right() : box.left();
+  int start_y = box.bottom();
+  // Acceptable tab vectors must have a minimum number of points,
+  // have a minimum acceptable length, and have a minimum gradient.
+  // The gradient corresponds to the skew angle.
+  // Ragged tabs don't need to satisfy the gradient condition, as they
+  // will always end up parallel to the vertical direction.
+  bool at_least_2_crossings = AtLeast2LineCrossings(&good_points);
+  if ((pt_count >= align_params.min_points && end_y - start_y >= align_params.min_length &&
+       (align_params.ragged || end_y - start_y >= abs(end_x - start_x) * kMinTabGradient)) ||
+      at_least_2_crossings) {
+    int confirmed_points = 0;
+    // Count existing confirmed points to see if vector is acceptable.
+    for (it.mark_cycle_pt(); !it.cycled_list(); it.forward()) {
+      bbox = it.data();
+      if (align_params.right_tab) {
+        if (bbox->right_tab_type() == align_params.confirmed_type) {
+          ++confirmed_points;
+        }
+      } else {
+        if (bbox->left_tab_type() == align_params.confirmed_type) {
+          ++confirmed_points;
+        }
+      }
+    }
+    // Ragged vectors are not allowed to use too many already used points.
+    if (!align_params.ragged || confirmed_points + confirmed_points < pt_count) {
+      const TBOX &box = bbox->bounding_box();
+      if (debug) {
+        tprintf("Confirming tab vector of %d pts starting at %d,%d\n", pt_count, box.left(),
+                box.bottom());
+      }
+      // Flag all the aligned neighbours as confirmed .
+      for (it.mark_cycle_pt(); !it.cycled_list(); it.forward()) {
+        bbox = it.data();
+        if (align_params.right_tab) {
+          bbox->set_right_tab_type(align_params.confirmed_type);
+        } else {
+          bbox->set_left_tab_type(align_params.confirmed_type);
+        }
+        if (debug) {
+          bbox->bounding_box().print();
+        }
+      }
+      // Now make the vector and return it.
+      TabVector *result =
+          TabVector::FitVector(align_params.alignment, align_params.vertical, ext_start_y,
+                               ext_end_y, &good_points, vertical_x, vertical_y);
+      result->set_intersects_other_lines(at_least_2_crossings);
+      if (debug) {
+        tprintf("Box was %d, %d\n", box.left(), box.bottom());
+        result->Print("After fitting");
+      }
+      return result;
+    } else if (debug) {
+      tprintf("Ragged tab used too many used points: %d out of %d\n", confirmed_points, pt_count);
+    }
+  } else if (debug) {
+    tprintf(
+        "Tab vector failed basic tests: pt count %d vs min %d, "
+        "length %d vs min %d, min grad %g\n",
+        pt_count, align_params.min_points, end_y - start_y, align_params.min_length,
+        abs(end_x - start_x) * kMinTabGradient);
+  }
+  return nullptr;
+}
+
+// Find a set of blobs that are aligned in the given vertical
+// direction with the given blob. Returns a list of aligned
+// blobs and the number in the list.
+// For other parameters see FindAlignedBlob below.
+int AlignedBlob::AlignTabs(const AlignedBlobParams &params, bool top_to_bottom, BLOBNBOX *bbox,
+                           BLOBNBOX_CLIST *good_points, int *end_y) {
+  int ptcount = 0;
+  BLOBNBOX_C_IT it(good_points);
+
+  TBOX box = bbox->bounding_box();
+  bool debug = WithinTestRegion(2, box.left(), box.bottom());
+  if (debug) {
+    tprintf("Starting alignment run at blob:");
+    box.print();
+  }
+  int x_start = params.right_tab ? box.right() : box.left();
+  while (bbox != nullptr) {
+    // Add the blob to the list if the appropriate side is a tab candidate,
+    // or if we are working on a ragged tab.
+    TabType type = params.right_tab ? bbox->right_tab_type() : bbox->left_tab_type();
+    if (((type != TT_NONE && type != TT_MAYBE_RAGGED) || params.ragged) &&
+        (it.empty() || it.data() != bbox)) {
+      if (top_to_bottom) {
+        it.add_before_then_move(bbox);
+      } else {
+        it.add_after_then_move(bbox);
+      }
+      ++ptcount;
+    }
+    // Find the next blob that is aligned with the current one.
+    // FindAlignedBlob guarantees that forward progress will be made in the
+    // top_to_bottom direction, and therefore eventually it will return nullptr,
+    // making this while (bbox != nullptr) loop safe.
+    bbox = FindAlignedBlob(params, top_to_bottom, bbox, x_start, end_y);
+    if (bbox != nullptr) {
+      box = bbox->bounding_box();
+      if (!params.ragged) {
+        x_start = params.right_tab ? box.right() : box.left();
+      }
+    }
+  }
+  if (debug) {
+    tprintf("Alignment run ended with %d pts at blob:", ptcount);
+    box.print();
+  }
+  return ptcount;
+}
+
+// Search vertically for a blob that is aligned with the input bbox.
+// The search parameters are determined by AlignedBlobParams.
+// top_to_bottom tells whether to search down or up.
+// The return value is nullptr if nothing was found in the search box
+// or if a blob was found in the gutter. On a nullptr return, end_y
+// is set to the edge of the search box or the leading edge of the
+// gutter blob if one was found.
+BLOBNBOX *AlignedBlob::FindAlignedBlob(const AlignedBlobParams &p, bool top_to_bottom,
+                                       BLOBNBOX *bbox, int x_start, int *end_y) {
+  TBOX box = bbox->bounding_box();
+  // If there are separator lines, get the column edges.
+  int left_column_edge = bbox->left_rule();
+  int right_column_edge = bbox->right_rule();
+  // start_y is used to guarantee that forward progress is made and the
+  // search does not go into an infinite loop. New blobs must extend the
+  // line beyond start_y.
+  int start_y = top_to_bottom ? box.bottom() : box.top();
+  if (WithinTestRegion(2, x_start, start_y)) {
+    tprintf("Column edges for blob at (%d,%d)->(%d,%d) are [%d, %d]\n", box.left(), box.top(),
+            box.right(), box.bottom(), left_column_edge, right_column_edge);
+  }
+  // Compute skew tolerance.
+  int skew_tolerance = p.max_v_gap / kMaxSkewFactor;
+  // Calculate xmin and xmax of the search box so that it contains
+  // all possibly relevant boxes up to p.max_v_gap above or below according
+  // to top_to_bottom.
+  // Start with a notion of vertical with the current estimate.
+  int x2 = (p.max_v_gap * p.vertical.x() + p.vertical.y() / 2) / p.vertical.y();
+  if (top_to_bottom) {
+    x2 = x_start - x2;
+    *end_y = start_y - p.max_v_gap;
+  } else {
+    x2 = x_start + x2;
+    *end_y = start_y + p.max_v_gap;
+  }
+  // Expand the box by an additional skew tolerance
+  int xmin = std::min(x_start, x2) - skew_tolerance;
+  int xmax = std::max(x_start, x2) + skew_tolerance;
+  // Now add direction-specific tolerances.
+  if (p.right_tab) {
+    xmax += p.min_gutter;
+    xmin -= p.l_align_tolerance;
+  } else {
+    xmax += p.r_align_tolerance;
+    xmin -= p.min_gutter;
+  }
+  // Setup a vertical search for an aligned blob.
+  BlobGridSearch vsearch(this);
+  if (WithinTestRegion(2, x_start, start_y)) {
+    tprintf("Starting %s %s search at %d-%d,%d, search_size=%d, gutter=%d\n",
+            p.ragged ? "Ragged" : "Aligned", p.right_tab ? "Right" : "Left", xmin, xmax, start_y,
+            p.max_v_gap, p.min_gutter);
+  }
+  vsearch.StartVerticalSearch(xmin, xmax, start_y);
+  // result stores the best real return value.
+  BLOBNBOX *result = nullptr;
+  // The backup_result is not a tab candidate and can be used if no
+  // real tab candidate result is found.
+  BLOBNBOX *backup_result = nullptr;
+  // neighbour is the blob that is currently being investigated.
+  BLOBNBOX *neighbour = nullptr;
+  while ((neighbour = vsearch.NextVerticalSearch(top_to_bottom)) != nullptr) {
+    if (neighbour == bbox) {
+      continue;
+    }
+    TBOX nbox = neighbour->bounding_box();
+    int n_y = (nbox.top() + nbox.bottom()) / 2;
+    if ((!top_to_bottom && n_y > start_y + p.max_v_gap) ||
+        (top_to_bottom && n_y < start_y - p.max_v_gap)) {
+      if (WithinTestRegion(2, x_start, start_y)) {
+        tprintf("Neighbour too far at (%d,%d)->(%d,%d)\n", nbox.left(), nbox.bottom(), nbox.right(),
+                nbox.top());
+      }
+      break; // Gone far enough.
+    }
+    // It is CRITICAL to ensure that forward progress is made, (strictly
+    // in/decreasing n_y) or the caller could loop infinitely, while
+    // waiting for a sequence of blobs in a line to end.
+    // NextVerticalSearch alone does not guarantee this, as there may be
+    // more than one blob in a grid cell. See comment in AlignTabs.
+    if ((n_y < start_y) != top_to_bottom || nbox.y_overlap(box)) {
+      continue; // Only look in the required direction.
+    }
+    if (result != nullptr && result->bounding_box().y_gap(nbox) > gridsize()) {
+      return result; // This result is clear.
+    }
+    if (backup_result != nullptr && p.ragged && result == nullptr &&
+        backup_result->bounding_box().y_gap(nbox) > gridsize()) {
+      return backup_result; // This result is clear.
+    }
+
+    // If the neighbouring blob is the wrong side of a separator line, then it
+    // "doesn't exist" as far as we are concerned.
+    int x_at_n_y = x_start + (n_y - start_y) * p.vertical.x() / p.vertical.y();
+    if (x_at_n_y < neighbour->left_crossing_rule() || x_at_n_y > neighbour->right_crossing_rule()) {
+      continue; // Separator line in the way.
+    }
+    int n_left = nbox.left();
+    int n_right = nbox.right();
+    int n_x = p.right_tab ? n_right : n_left;
+    if (WithinTestRegion(2, x_start, start_y)) {
+      tprintf("neighbour at (%d,%d)->(%d,%d), n_x=%d, n_y=%d, xatn=%d\n", nbox.left(),
+              nbox.bottom(), nbox.right(), nbox.top(), n_x, n_y, x_at_n_y);
+    }
+    if (p.right_tab && n_left < x_at_n_y + p.min_gutter &&
+        n_right > x_at_n_y + p.r_align_tolerance &&
+        (p.ragged || n_left < x_at_n_y + p.gutter_fraction * nbox.height())) {
+      // In the gutter so end of line.
+      if (bbox->right_tab_type() >= TT_MAYBE_ALIGNED) {
+        bbox->set_right_tab_type(TT_DELETED);
+      }
+      *end_y = top_to_bottom ? nbox.top() : nbox.bottom();
+      if (WithinTestRegion(2, x_start, start_y)) {
+        tprintf("gutter\n");
+      }
+      return nullptr;
+    }
+    if (!p.right_tab && n_left < x_at_n_y - p.l_align_tolerance &&
+        n_right > x_at_n_y - p.min_gutter &&
+        (p.ragged || n_right > x_at_n_y - p.gutter_fraction * nbox.height())) {
+      // In the gutter so end of line.
+      if (bbox->left_tab_type() >= TT_MAYBE_ALIGNED) {
+        bbox->set_left_tab_type(TT_DELETED);
+      }
+      *end_y = top_to_bottom ? nbox.top() : nbox.bottom();
+      if (WithinTestRegion(2, x_start, start_y)) {
+        tprintf("gutter\n");
+      }
+      return nullptr;
+    }
+    if ((p.right_tab && neighbour->leader_on_right()) ||
+        (!p.right_tab && neighbour->leader_on_left())) {
+      continue; // Neighbours of leaders are not allowed to be used.
+    }
+    if (n_x <= x_at_n_y + p.r_align_tolerance && n_x >= x_at_n_y - p.l_align_tolerance) {
+      // Aligned so keep it. If it is a marked tab save it as result,
+      // otherwise keep it as backup_result to return in case of later failure.
+      if (WithinTestRegion(2, x_start, start_y)) {
+        tprintf("aligned, seeking%d, l=%d, r=%d\n", p.right_tab, neighbour->left_tab_type(),
+                neighbour->right_tab_type());
+      }
+      TabType n_type = p.right_tab ? neighbour->right_tab_type() : neighbour->left_tab_type();
+      if (n_type != TT_NONE && (p.ragged || n_type != TT_MAYBE_RAGGED)) {
+        if (result == nullptr) {
+          result = neighbour;
+        } else {
+          // Keep the closest neighbour by Euclidean distance.
+          // This prevents it from picking a tab blob in another column.
+          const TBOX &old_box = result->bounding_box();
+          int x_diff = p.right_tab ? old_box.right() : old_box.left();
+          x_diff -= x_at_n_y;
+          int y_diff = (old_box.top() + old_box.bottom()) / 2 - start_y;
+          int old_dist = x_diff * x_diff + y_diff * y_diff;
+          x_diff = n_x - x_at_n_y;
+          y_diff = n_y - start_y;
+          int new_dist = x_diff * x_diff + y_diff * y_diff;
+          if (new_dist < old_dist) {
+            result = neighbour;
+          }
+        }
+      } else if (backup_result == nullptr) {
+        if (WithinTestRegion(2, x_start, start_y)) {
+          tprintf("Backup\n");
+        }
+        backup_result = neighbour;
+      } else {
+        TBOX backup_box = backup_result->bounding_box();
+        if ((p.right_tab && backup_box.right() < nbox.right()) ||
+            (!p.right_tab && backup_box.left() > nbox.left())) {
+          if (WithinTestRegion(2, x_start, start_y)) {
+            tprintf("Better backup\n");
+          }
+          backup_result = neighbour;
+        }
+      }
+    }
+  }
+  return result != nullptr ? result : backup_result;
+}
+
+} // namespace tesseract.