[PATCH] Pivot table: New feature to suppress the display of rows/cols which are empty.

[John Darrington]

This change adds a feature to the pivot table implementation such that columns
and/or rows which are completely empty (except for the headings) are not
rendered.

* src/output/pivot-output.c (pivot_table_submit_layer): Keep an array recording
the occupancy of each row and column. (compose_headings): Use it to hide empty
rows/columns.
* src/output/pivot-table.h [struct pivot_table]: New members hide_empty_columns,
hide_empty_rows.
---
 src/output/pivot-output.c | 83 ++++++++++++++++++++++++++++++-----------------
 src/output/pivot-table.h  |  2 ++
 2 files changed, 56 insertions(+), 29 deletions(-)

diff --git a/src/output/pivot-output.c b/src/output/pivot-output.c
index 69a6f7fec..27ece3dc4 100644
--- a/src/output/pivot-output.c
+++ b/src/output/pivot-output.c
@@ -22,6 +22,7 @@
 
 #include "data/settings.h"
 #include "libpspp/assertion.h"
+#include "libpspp/sparse-array.h"
 #include "libpspp/pool.h"
 #include "output/tab.h"
 #include "output/table.h"
@@ -190,7 +191,8 @@ compose_headings (struct tab_table *t,
                   struct footnote **footnotes,
                   enum settings_value_show show_values,
                   enum settings_value_show show_variables,
-                  bool rotate_inner_labels, bool rotate_outer_labels)
+                  bool rotate_inner_labels, bool rotate_outer_labels,
+                  const struct sparse_array *occupied)
 {
   enum table_axis b = !a;
   int b_size = a_axis->label_depth;
@@ -213,7 +215,7 @@ compose_headings (struct tab_table *t,
             {
               const struct pivot_category *c = find_category (
                 d, dim_index, column_enumeration + x1 * stride, row_ofs);
-              if (!c)
+              if (!c || !sparse_array_get (occupied, x1))
                 {
                   x1++;
                   continue;
@@ -363,6 +365,50 @@ pivot_table_submit_layer (const struct pivot_table *pt,
       free (content);
     }
 
+  size_t *dindexes = xcalloc (pt->n_dimensions, sizeof *dindexes);
+  size_t y = 0;
+  struct sparse_array *occupied_rows = sparse_array_create (1);
+  struct sparse_array *occupied_columns = sparse_array_create (1);
+  PIVOT_ENUMERATION_FOR_EACH (pindexes[PIVOT_AXIS_ROW], row_enumeration,
+                              &pt->axes[PIVOT_AXIS_ROW])
+    {
+      size_t x = 0;
+      if (! pt->hide_empty_rows)
+        sparse_array_insert (occupied_rows, y);
+
+      PIVOT_ENUMERATION_FOR_EACH (pindexes[PIVOT_AXIS_COLUMN],
+                                  column_enumeration,
+                                  &pt->axes[PIVOT_AXIS_COLUMN])
+        {
+          if (! pt->hide_empty_columns)
+            {
+              if (! sparse_array_get (occupied_columns, x))
+                sparse_array_insert (occupied_columns, x);
+            }
+          pivot_table_convert_indexes_ptod (pt, pindexes, dindexes);
+          const struct pivot_value *value = pivot_table_get (pt, dindexes);
+          if (value)
+          {
+            if (! sparse_array_get (occupied_columns, x))
+              sparse_array_insert (occupied_columns, x);
+
+            if (! sparse_array_get (occupied_rows, y))
+              sparse_array_insert (occupied_rows, y);
+          }
+          fill_cell (table,
+                     x + stub[H], y + stub[V],
+                     x + stub[H], y + stub[V],
+                     &pt->areas[PIVOT_AREA_DATA], PIVOT_AREA_DATA,
+                     value, footnotes,
+                     pt->show_values, pt->show_variables, false);
+
+          x++;
+        }
+
+      y++;
+    }
+  free (dindexes);
+
   compose_headings (table,
                     &pt->axes[PIVOT_AXIS_COLUMN], H, &pt->axes[PIVOT_AXIS_ROW],
                     pt->borders,
@@ -375,7 +421,8 @@ pivot_table_submit_layer (const struct pivot_table *pt,
                     PIVOT_AREA_COLUMN_LABELS,
                     &pt->areas[PIVOT_AREA_CORNER], footnotes,
                     pt->show_values, pt->show_variables,
-                    pt->rotate_inner_column_labels, false);
+                    pt->rotate_inner_column_labels, false,
+                    occupied_columns);
 
   compose_headings (table,
                     &pt->axes[PIVOT_AXIS_ROW], V, &pt->axes[PIVOT_AXIS_COLUMN],
@@ -389,33 +436,11 @@ pivot_table_submit_layer (const struct pivot_table *pt,
                     PIVOT_AREA_ROW_LABELS,
                     &pt->areas[PIVOT_AREA_CORNER], footnotes,
                     pt->show_values, pt->show_variables,
-                    false, pt->rotate_outer_row_labels);
+                    false, pt->rotate_outer_row_labels,
+                    occupied_rows);
 
-  size_t *dindexes = xcalloc (pt->n_dimensions, sizeof *dindexes);
-  size_t y = 0;
-  PIVOT_ENUMERATION_FOR_EACH (pindexes[PIVOT_AXIS_ROW], row_enumeration,
-                              &pt->axes[PIVOT_AXIS_ROW])
-    {
-      size_t x = 0;
-      PIVOT_ENUMERATION_FOR_EACH (pindexes[PIVOT_AXIS_COLUMN],
-                                  column_enumeration,
-                                  &pt->axes[PIVOT_AXIS_COLUMN])
-        {
-          pivot_table_convert_indexes_ptod (pt, pindexes, dindexes);
-          const struct pivot_value *value = pivot_table_get (pt, dindexes);
-          fill_cell (table,
-                     x + stub[H], y + stub[V],
-                     x + stub[H], y + stub[V],
-                     &pt->areas[PIVOT_AREA_DATA], PIVOT_AREA_DATA,
-                     value, footnotes,
-                     pt->show_values, pt->show_variables, false);
-
-          x++;
-        }
-
-      y++;
-    }
-  free (dindexes);
+  sparse_array_destroy (occupied_rows);
+  sparse_array_destroy (occupied_columns);
 
   if (pt->corner_text && stub[H] && stub[V])
     fill_cell (table, 0, 0, stub[H] - 1, stub[V] - 1,
diff --git a/src/output/pivot-table.h b/src/output/pivot-table.h
index 6104cb131..1164abb1d 100644
--- a/src/output/pivot-table.h
+++ b/src/output/pivot-table.h
@@ -371,6 +371,8 @@ struct pivot_table
     bool row_labels_in_corner;
     bool show_grid_lines;
     bool omit_empty;
+    bool hide_empty_columns;
+    bool hide_empty_rows;
     size_t *current_layer; /* axis[PIVOT_AXIS_LAYER]->n_dimensions elements. */
     char *table_look;
     enum settings_value_show show_values;
-- 
2.11.0