--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mupdf-source/thirdparty/tesseract/src/textord/tabfind.h	Mon Sep 15 11:43:07 2025 +0200
@@ -0,0 +1,363 @@
+///////////////////////////////////////////////////////////////////////
+// File:        tabfind.h
+// Description: Subclass of BBGrid to find tabstops.
+// 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.
+//
+///////////////////////////////////////////////////////////////////////
+
+#ifndef TESSERACT_TEXTORD_TABFIND_H_
+#define TESSERACT_TEXTORD_TABFIND_H_
+
+#include <functional> // for std::function
+#include "alignedblob.h"
+#include "linefind.h"
+#include "tabvector.h"
+
+class BLOBNBOX;
+class BLOBNBOX_LIST;
+class TO_BLOCK;
+class ScrollView;
+struct Pix;
+
+namespace tesseract {
+
+using WidthCallback = std::function<bool(int)>;
+
+struct AlignedBlobParams;
+class ColPartitionGrid;
+
+/** Pixel resolution of column width estimates. */
+const int kColumnWidthFactor = 20;
+
+/**
+ * The TabFind class contains code to find tab-stops and maintain the
+ * vectors_ list of tab vectors.
+ * Also provides an interface to find neighbouring blobs
+ * in the grid of BLOBNBOXes that is used by multiple subclasses.
+ * Searching is a complex operation because of the need to enforce
+ * rule/separator lines, and tabstop boundaries, (when available), so
+ * as the holder of the list of TabVectors this class provides the functions.
+ */
+class TESS_API TabFind : public AlignedBlob {
+public:
+  TabFind(int gridsize, const ICOORD &bleft, const ICOORD &tright, TabVector_LIST *vlines,
+          int vertical_x, int vertical_y, int resolution);
+  ~TabFind() override;
+
+  /**
+   * Insert a list of blobs into the given grid (not necessarily this).
+   * See InsertBlob for the other arguments.
+   * It would seem to make more sense to swap this and grid, but this way
+   * around allows grid to not be derived from TabFind, eg a ColPartitionGrid,
+   * while the grid that provides the tab stops(this) has to be derived from
+   * TabFind.
+   */
+  void InsertBlobsToGrid(bool h_spread, bool v_spread, BLOBNBOX_LIST *blobs,
+                         BBGrid<BLOBNBOX, BLOBNBOX_CLIST, BLOBNBOX_C_IT> *grid);
+
+  /**
+   * Insert a single blob into the given grid (not necessarily this).
+   * If h_spread, then all cells covered horizontally by the box are
+   * used, otherwise, just the bottom-left. Similarly for v_spread.
+   * A side effect is that the left and right rule edges of the blob are
+   * set according to the tab vectors in this (not grid).
+   */
+  bool InsertBlob(bool h_spread, bool v_spread, BLOBNBOX *blob,
+                  BBGrid<BLOBNBOX, BLOBNBOX_CLIST, BLOBNBOX_C_IT> *grid);
+  // Calls SetBlobRuleEdges for all the blobs in the given block.
+  void SetBlockRuleEdges(TO_BLOCK *block);
+  // Sets the left and right rule and crossing_rules for the blobs in the given
+  // list by finding the next outermost tabvectors for each blob.
+  void SetBlobRuleEdges(BLOBNBOX_LIST *blobs);
+
+  // Returns the gutter width of the given TabVector between the given y limits.
+  // Also returns x-shift to be added to the vector to clear any intersecting
+  // blobs. The shift is deducted from the returned gutter.
+  // If ignore_unmergeables is true, then blobs of UnMergeableType are
+  // ignored as if they don't exist. (Used for text on image.)
+  // max_gutter_width is used as the maximum width worth searching for in case
+  // there is nothing near the TabVector.
+  int GutterWidth(int bottom_y, int top_y, const TabVector &v, bool ignore_unmergeables,
+                  int max_gutter_width, int *required_shift);
+  /**
+   * Find the gutter width and distance to inner neighbour for the given blob.
+   */
+  void GutterWidthAndNeighbourGap(int tab_x, int mean_height, int max_gutter, bool left,
+                                  BLOBNBOX *bbox, int *gutter_width, int *neighbour_gap);
+
+  /**
+   * Return the x-coord that corresponds to the right edge for the given
+   * box. If there is a rule line to the right that vertically overlaps it,
+   * then return the x-coord of the rule line, otherwise return the right
+   * edge of the page. For details see RightTabForBox below.
+   */
+  int RightEdgeForBox(const TBOX &box, bool crossing, bool extended);
+  /**
+   * As RightEdgeForBox, but finds the left Edge instead.
+   */
+  int LeftEdgeForBox(const TBOX &box, bool crossing, bool extended);
+
+  /**
+   * Return the TabVector that corresponds to the right edge for the given
+   * box. If there is a TabVector to the right that vertically overlaps it,
+   * then return it, otherwise return nullptr. Note that Right and Left refer
+   * to the position of the TabVector, not its type, ie RightTabForBox
+   * returns the nearest TabVector to the right of the box, regardless of
+   * its type.
+   * If a TabVector crosses right through the box (as opposed to grazing one
+   * edge or missing entirely), then crossing false will ignore such a line.
+   * Crossing true will return the line for BOTH left and right edges.
+   * If extended is true, then TabVectors are considered to extend to their
+   * extended_start/end_y, otherwise, just the startpt_ and endpt_.
+   * These functions make use of an internal iterator to the vectors_ list
+   * for speed when used repeatedly on neighbouring boxes. The caveat is
+   * that the iterator must be updated whenever the list is modified.
+   */
+  TabVector *RightTabForBox(const TBOX &box, bool crossing, bool extended);
+  /**
+   * As RightTabForBox, but finds the left TabVector instead.
+   */
+  TabVector *LeftTabForBox(const TBOX &box, bool crossing, bool extended);
+
+  /**
+   * Return true if the given width is close to one of the common
+   * widths in column_widths_.
+   */
+  bool CommonWidth(int width);
+  /**
+   * Return true if the sizes are more than a
+   * factor of 2 different.
+   */
+  static bool DifferentSizes(int size1, int size2);
+  /**
+   * Return true if the sizes are more than a
+   * factor of 5 different.
+   */
+  static bool VeryDifferentSizes(int size1, int size2);
+
+  /**
+   * Return a callback for testing CommonWidth.
+   */
+  WidthCallback WidthCB() {
+    return width_cb_;
+  }
+
+  /**
+   * Return the coords at which to draw the image backdrop.
+   */
+  const ICOORD &image_origin() const {
+    return image_origin_;
+  }
+
+protected:
+  /**
+// Accessors
+ */
+  TabVector_LIST *vectors() {
+    return &vectors_;
+  }
+  TabVector_LIST *dead_vectors() {
+    return &dead_vectors_;
+  }
+
+  /**
+   * Top-level function to find TabVectors in an input page block.
+   * Returns false if the detected skew angle is impossible.
+   * Applies the detected skew angle to deskew the tabs, blobs and part_grid.
+   * tabfind_aligned_gap_fraction should be the value of parameter
+   * textord_tabfind_aligned_gap_fraction
+   */
+  bool FindTabVectors(TabVector_LIST *hlines, BLOBNBOX_LIST *image_blobs, TO_BLOCK *block,
+                      int min_gutter_width, double tabfind_aligned_gap_fraction,
+                      ColPartitionGrid *part_grid, FCOORD *deskew, FCOORD *reskew);
+
+  // Top-level function to not find TabVectors in an input page block,
+  // but setup for single column mode.
+  void DontFindTabVectors(BLOBNBOX_LIST *image_blobs, TO_BLOCK *block, FCOORD *deskew,
+                          FCOORD *reskew);
+
+  // Cleans up the lists of blobs in the block ready for use by TabFind.
+  // Large blobs that look like text are moved to the main blobs list.
+  // Main blobs that are superseded by the image blobs are deleted.
+  void TidyBlobs(TO_BLOCK *block);
+
+  // Helper function to setup search limits for *TabForBox.
+  void SetupTabSearch(int x, int y, int *min_key, int *max_key);
+
+  /**
+   * Display the tab vectors found in this grid.
+   */
+  ScrollView *DisplayTabVectors(ScrollView *tab_win);
+
+  // First part of FindTabVectors, which may be used twice if the text
+  // is mostly of vertical alignment.  If find_vertical_text flag is
+  // true, this finds vertical textlines in possibly rotated blob space.
+  // In other words, when the page has mostly vertical lines and is rotated,
+  // setting this to true will find horizontal lines on the page.
+  // tabfind_aligned_gap_fraction should be the value of parameter
+  // textord_tabfind_aligned_gap_fraction
+  ScrollView *FindInitialTabVectors(BLOBNBOX_LIST *image_blobs, int min_gutter_width,
+                                    double tabfind_aligned_gap_fraction, TO_BLOCK *block);
+
+  // Apply the given rotation to the given list of blobs.
+  static void RotateBlobList(const FCOORD &rotation, BLOBNBOX_LIST *blobs);
+
+  // Flip the vertical and horizontal lines and rotate the grid ready
+  // for working on the rotated image.
+  // The min_gutter_width will be adjusted to the median gutter width between
+  // vertical tabs to set a better threshold for tabboxes in the 2nd pass.
+  void ResetForVerticalText(const FCOORD &rotate, const FCOORD &rerotate,
+                            TabVector_LIST *horizontal_lines, int *min_gutter_width);
+
+  // Clear the grid and get rid of the tab vectors, but not separators,
+  // ready to start again.
+  void Reset();
+
+  // Reflect the separator tab vectors and the grids in the y-axis.
+  // Can only be called after Reset!
+  void ReflectInYAxis();
+
+private:
+  // For each box in the grid, decide whether it is a candidate tab-stop,
+  // and if so add it to the left and right tab boxes.
+  // tabfind_aligned_gap_fraction should be the value of parameter
+  // textord_tabfind_aligned_gap_fraction
+  ScrollView *FindTabBoxes(int min_gutter_width, double tabfind_aligned_gap_fraction);
+
+  // Return true if this box looks like a candidate tab stop, and set
+  // the appropriate tab type(s) to TT_UNCONFIRMED.
+  // tabfind_aligned_gap_fraction should be the value of parameter
+  // textord_tabfind_aligned_gap_fraction
+  bool TestBoxForTabs(BLOBNBOX *bbox, int min_gutter_width, double tabfind_aligned_gap_fraction);
+
+  // Returns true if there is nothing in the rectangle of width min_gutter to
+  // the left of bbox.
+  bool ConfirmRaggedLeft(BLOBNBOX *bbox, int min_gutter);
+  // Returns true if there is nothing in the rectangle of width min_gutter to
+  // the right of bbox.
+  bool ConfirmRaggedRight(BLOBNBOX *bbox, int min_gutter);
+  // Returns true if there is nothing in the given search_box that vertically
+  // overlaps target_box other than target_box itself.
+  bool NothingYOverlapsInBox(const TBOX &search_box, const TBOX &target_box);
+
+  // Fills the list of TabVector with the tabstops found in the grid,
+  // and estimates the logical vertical direction.
+  void FindAllTabVectors(int min_gutter_width);
+  // Helper for FindAllTabVectors finds the vectors of a particular type.
+  int FindTabVectors(int search_size_multiple, TabAlignment alignment, int min_gutter_width,
+                     TabVector_LIST *vectors, int *vertical_x, int *vertical_y);
+  // Finds a vector corresponding to a tabstop running through the
+  // given box of the given alignment type.
+  // search_size_multiple is a multiple of height used to control
+  // the size of the search.
+  // vertical_x and y are updated with an estimate of the real
+  // vertical direction. (skew finding.)
+  // Returns nullptr if no decent tabstop can be found.
+  TabVector *FindTabVector(int search_size_multiple, int min_gutter_width, TabAlignment alignment,
+                           BLOBNBOX *bbox, int *vertical_x, int *vertical_y);
+
+  // Set the vertical_skew_ member from the given vector and refit
+  // all vectors parallel to the skew vector.
+  void SetVerticalSkewAndParallelize(int vertical_x, int vertical_y);
+
+  // Sort all the current vectors using the vertical_skew_ vector.
+  void SortVectors();
+
+  // Evaluate all the current tab vectors.
+  void EvaluateTabs();
+
+  // Trace textlines from one side to the other of each tab vector, saving
+  // the most frequent column widths found in a list so that a given width
+  // can be tested for being a common width with a simple callback function.
+  void ComputeColumnWidths(ScrollView *tab_win, ColPartitionGrid *part_grid);
+
+  // Finds column width and:
+  //   if col_widths is not null (pass1):
+  //     pair-up tab vectors with existing ColPartitions and accumulate widths.
+  //   else (pass2):
+  //     find the largest real partition width for each recorded column width,
+  //     to be used as the minimum acceptable width.
+  void ApplyPartitionsToColumnWidths(ColPartitionGrid *part_grid, STATS *col_widths);
+
+  // Helper makes the list of common column widths in column_widths_ from the
+  // input col_widths. Destroys the content of col_widths by repeatedly
+  // finding the mode and erasing the peak.
+  void MakeColumnWidths(int col_widths_size, STATS *col_widths);
+
+  // Mark blobs as being in a vertical text line where that is the case.
+  void MarkVerticalText();
+
+  // Returns the median gutter width between pairs of matching tab vectors
+  // assuming they are sorted left-to-right.  If there are too few data
+  // points (< kMinLinesInColumn), then 0 is returned.
+  int FindMedianGutterWidth(TabVector_LIST *tab_vectors);
+
+  // Find the next adjacent (to left or right) blob on this text line,
+  // with the constraint that it must vertically significantly overlap
+  // the [top_y, bottom_y] range.
+  // If ignore_images is true, then blobs with aligned_text() < 0 are treated
+  // as if they do not exist.
+  BLOBNBOX *AdjacentBlob(const BLOBNBOX *bbox, bool look_left, bool ignore_images,
+                         double min_overlap_fraction, int gap_limit, int top_y, int bottom_y);
+
+  // Add a bi-directional partner relationship between the left
+  // and the right. If one (or both) of the vectors is a separator,
+  // extend a nearby extendable vector or create a new one of the
+  // correct type, using the given left or right blob as a guide.
+  void AddPartnerVector(BLOBNBOX *left_blob, BLOBNBOX *right_blob, TabVector *left,
+                        TabVector *right);
+
+  /**
+   * Remove separators and unused tabs from the main vectors_ list
+   * to the dead_vectors_ list.
+   */
+  void CleanupTabs();
+
+  /**
+   * Deskew the tab vectors and blobs, computing the rotation and resetting
+   * the storked vertical_skew_. The deskew inverse is returned in reskew.
+   * Returns false if the detected skew angle is impossible.
+   */
+  bool Deskew(TabVector_LIST *hlines, BLOBNBOX_LIST *image_blobs, TO_BLOCK *block, FCOORD *deskew,
+              FCOORD *reskew);
+
+  // Compute the rotation required to deskew, and its inverse rotation.
+  void ComputeDeskewVectors(FCOORD *deskew, FCOORD *reskew);
+
+  /**
+   * Compute and apply constraints to the end positions of TabVectors so
+   * that where possible partners end at the same y coordinate.
+   */
+  void ApplyTabConstraints();
+
+protected:
+  ICOORD vertical_skew_; ///< Estimate of true vertical in this image.
+  int resolution_;       ///< Of source image in pixels per inch.
+private:
+  ICOORD image_origin_;         ///< Top-left of image in deskewed coords
+  TabVector_LIST vectors_;      ///< List of rule line and tabstops.
+  TabVector_IT v_it_;           ///< Iterator for searching vectors_.
+  TabVector_LIST dead_vectors_; ///< Separators and unpartnered tab vectors.
+  // List of commonly occurring width ranges with x=min and y=max.
+  ICOORDELT_LIST column_widths_; ///< List of commonly occurring width ranges.
+  /** Callback to test an int for being a common width. */
+  WidthCallback width_cb_;
+  // Sets of bounding boxes that are candidate tab stops.
+  std::vector<BLOBNBOX *> left_tab_boxes_;
+  std::vector<BLOBNBOX *> right_tab_boxes_;
+};
+
+} // namespace tesseract.
+
+#endif // TESSERACT_TEXTORD_TABFIND_H_