Merge branch 'item-offset' into 'main'

Keep offsets for items

See merge request GNOME/pango!451

7 files changed, 138 insertions, 55 deletions

diff --git a/pango/itemize.c b/pango/itemize.c
index 27a9865d..11bc2513 100644
--- a/pango/itemize.c
+++ b/pango/itemize.c
@@ -32,6 +32,7 @@
 #include "pango-script-private.h"
 #include "pango-emoji-private.h"
 #include "pango-attributes-private.h"
+#include "pango-item-private.h"
 
 
 /* {{{ Font cache */
@@ -700,7 +701,7 @@ itemize_state_add_character (ItemizeState *state,
         break;
     }
 
-  state->item->analysis.flags = state->centered_baseline ? PANGO_ANALYSIS_FLAG_CENTERED_BASELINE : 0;
+  state->item->analysis.flags |= state->centered_baseline ? PANGO_ANALYSIS_FLAG_CENTERED_BASELINE : 0;
 
   state->item->analysis.script = state->script;
   state->item->analysis.language = state->derived_lang;
@@ -1021,21 +1022,26 @@ itemize_state_finish (ItemizeState *state)
 /* }}} */
 /* {{{ Public API */
 
-/* Like pango_itemize, but takes a font description */
+/* Like pango_itemize_with_base_dir, but takes a font description */
 GList *
 pango_itemize_with_font (PangoContext               *context,
+                         PangoDirection              base_dir,
                          const char                 *text,
                          int                         start_index,
                          int                         length,
+                         PangoAttrList              *attrs,
+                         PangoAttrIterator          *cached_iter,
                          const PangoFontDescription *desc)
 {
   ItemizeState state;
+  GList *items;
+  int char_offset;
 
-  if (length == 0)
+  if (length == 0 || g_utf8_get_char (text + start_index) == '\0')
     return NULL;
 
-  itemize_state_init (&state, context, text, context->base_dir, start_index, length,
-                      NULL, NULL, desc);
+  itemize_state_init (&state, context, text, base_dir, start_index, length,
+                      attrs, cached_iter, desc);
 
   do
     itemize_state_process_run (&state);
@@ -1043,7 +1049,18 @@ pango_itemize_with_font (PangoContext               *context,
 
   itemize_state_finish (&state);
 
-  return g_list_reverse (state.result);
+  items = g_list_reverse (state.result);
+
+  /* Compute the char offset for each item */
+  char_offset = 0;
+  for (GList *l = items; l; l = l->next)
+    {
+      PangoItemPrivate *item = l->data;
+      item->char_offset = char_offset;
+      char_offset += item->num_chars;
+    }
+
+  return items;
 }
 
 /**
@@ -1079,26 +1096,15 @@ pango_itemize_with_base_dir (PangoContext      *context,
                              PangoAttrList     *attrs,
                              PangoAttrIterator *cached_iter)
 {
-  ItemizeState state;
-
   g_return_val_if_fail (context != NULL, NULL);
   g_return_val_if_fail (start_index >= 0, NULL);
   g_return_val_if_fail (length >= 0, NULL);
   g_return_val_if_fail (length == 0 || text != NULL, NULL);
 
-  if (length == 0 || g_utf8_get_char (text + start_index) == '\0')
-    return NULL;
-
-  itemize_state_init (&state, context, text, base_dir, start_index, length,
-                      attrs, cached_iter, NULL);
-
-  do
-    itemize_state_process_run (&state);
-  while (itemize_state_next (&state));
-
-  itemize_state_finish (&state);
-
-  return g_list_reverse (state.result);
+  return pango_itemize_with_font (context, base_dir,
+                                  text, start_index, length,
+                                  attrs, cached_iter,
+                                  NULL);
 }
 
 /**
@@ -1142,8 +1148,10 @@ pango_itemize (PangoContext      *context,
   g_return_val_if_fail (length >= 0, NULL);
   g_return_val_if_fail (length == 0 || text != NULL, NULL);
 
-  return pango_itemize_with_base_dir (context, context->base_dir,
-                                      text, start_index, length, attrs, cached_iter);
+  return pango_itemize_with_font (context, context->base_dir,
+                                  text, start_index, length,
+                                  attrs, cached_iter,
+                                  NULL);
 }
 
 /* }}} */
diff --git a/pango/pango-context-private.h b/pango/pango-context-private.h
index 240c07d4..d65406e1 100644
--- a/pango/pango-context-private.h
+++ b/pango/pango-context-private.h
@@ -51,9 +51,12 @@ struct _PangoContext
 };
 
 GList *         pango_itemize_with_font (PangoContext               *context,
+                                         PangoDirection              base_dir,
                                          const char                 *text,
                                          int                         start_index,
                                          int                         length,
+                                         PangoAttrList              *attrs,
+                                         PangoAttrIterator          *cached_iter,
                                          const PangoFontDescription *desc);
 
 
diff --git a/pango/pango-context.c b/pango/pango-context.c
index d76b0ae2..2301138f 100644
--- a/pango/pango-context.c
+++ b/pango/pango-context.c
@@ -712,7 +712,10 @@ pango_context_get_metrics (PangoContext               *context,
 
   sample_str = pango_language_get_sample_string (language);
   text_len = strlen (sample_str);
-  items = pango_itemize_with_font (context, sample_str, 0, text_len, desc);
+  items = pango_itemize_with_font (context, context->base_dir,
+                                   sample_str, 0, text_len,
+                                   NULL, NULL,
+                                   desc);
 
   update_metrics_from_items (metrics, language, sample_str, text_len, items);
 
diff --git a/pango/pango-item-private.h b/pango/pango-item-private.h
new file mode 100644
index 00000000..8bb7e1cd
--- /dev/null
+++ b/pango/pango-item-private.h
@@ -0,0 +1,73 @@
+/* Pango
+ *
+ * Copyright (C) 2021 Matthias Clasen
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#ifndef __PANGO_ITEM_PRIVATE_H__
+#define __PANGO_ITEM_PRIVATE_H__
+
+#include <pango/pango-item.h>
+
+G_BEGIN_DECLS
+
+/**
+ * We have to do some extra work for adding the char_offset field
+ * to PangoItem to preserve ABI in the face of pango's open-coded
+ * structs.
+ *
+ * Internally, pango uses the PangoItemPrivate type, and we use
+ * a bit in the PangoAnalysis flags to indicate whether we are
+ * dealing with a PangoItemPrivate struct or not.
+ */
+
+#define PANGO_ANALYSIS_FLAG_HAS_CHAR_OFFSET (1 << 7)
+
+typedef struct _PangoItemPrivate PangoItemPrivate;
+
+#ifdef __x86_64__
+
+struct _PangoItemPrivate
+{
+  int offset;
+  int length;
+  int num_chars;
+  int char_offset;
+  PangoAnalysis analysis;
+};
+
+#else
+
+struct _PangoItemPrivate
+{
+  int offset;
+  int length;
+  int num_chars;
+  PangoAnalysis analysis;
+  int char_offset;
+}
+
+#endif
+
+G_STATIC_ASSERT (offsetof (PangoItem, offset) == offsetof (PangoItemPrivate, offset));
+G_STATIC_ASSERT (offsetof (PangoItem, length) == offsetof (PangoItemPrivate, length));
+G_STATIC_ASSERT (offsetof (PangoItem, num_chars) == offsetof (PangoItemPrivate, num_chars));
+G_STATIC_ASSERT (offsetof (PangoItem, analysis) == offsetof (PangoItemPrivate, analysis));
+
+G_END_DECLS
+
+#endif /* __PANGO_ITEM_PRIVATE_H__ */
diff --git a/pango/pango-item.c b/pango/pango-item.c
index ce38e6d2..484d5f1f 100644
--- a/pango/pango-item.c
+++ b/pango/pango-item.c
@@ -21,7 +21,7 @@
 
 #include "config.h"
 #include "pango-attributes.h"
-#include "pango-item.h"
+#include "pango-item-private.h"
 #include "pango-impl-utils.h"
 
 /**
@@ -35,9 +35,11 @@
 PangoItem *
 pango_item_new (void)
 {
-  PangoItem *result = g_slice_new0 (PangoItem);
+  PangoItemPrivate *result = g_slice_new0 (PangoItemPrivate);
 
-  return result;
+  result->analysis.flags |= PANGO_ANALYSIS_FLAG_HAS_CHAR_OFFSET;
+
+  return (PangoItem *)result;
 }
 
 /**
@@ -57,11 +59,13 @@ pango_item_copy (PangoItem *item)
   if (item == NULL)
     return NULL;
 
-  result = g_slice_new (PangoItem);
+  result = pango_item_new ();
 
   result->offset = item->offset;
   result->length = item->length;
   result->num_chars = item->num_chars;
+  if (item->analysis.flags & PANGO_ANALYSIS_FLAG_HAS_CHAR_OFFSET)
+    ((PangoItemPrivate *)result)->char_offset = ((PangoItemPrivate *)item)->char_offset;
 
   result->analysis = item->analysis;
   if (result->analysis.font)
@@ -101,7 +105,10 @@ pango_item_free (PangoItem *item)
   if (item->analysis.font)
     g_object_unref (item->analysis.font);
 
-  g_slice_free (PangoItem, item);
+  if (item->analysis.flags & PANGO_ANALYSIS_FLAG_HAS_CHAR_OFFSET)
+    g_slice_free (PangoItemPrivate, (PangoItemPrivate *)item);
+  else
+    g_slice_free (PangoItem, item);
 }
 
 G_DEFINE_BOXED_TYPE (PangoItem, pango_item,
@@ -151,6 +158,8 @@ pango_item_split (PangoItem *orig,
   orig->offset += split_index;
   orig->length -= split_index;
   orig->num_chars -= split_offset;
+  if (orig->analysis.flags & PANGO_ANALYSIS_FLAG_HAS_CHAR_OFFSET)
+    ((PangoItemPrivate *)orig)->char_offset += split_offset;
 
   return new_item;
 }
diff --git a/pango/pango-item.h b/pango/pango-item.h
index 9e0596f2..8122be19 100644
--- a/pango/pango-item.h
+++ b/pango/pango-item.h
@@ -100,6 +100,7 @@ struct _PangoAnalysis
  * @offset: byte offset of the start of this item in text.
  * @length: length of this item in bytes.
  * @num_chars: number of Unicode characters in the item.
+ * @char_offset: character offset of the start of this item in text. Since 1.50
  * @analysis: analysis results for the item.
  *
  * The `PangoItem` structure stores information about a segment of text.
@@ -109,9 +110,9 @@ struct _PangoAnalysis
  */
 struct _PangoItem
 {
-  gint offset;
-  gint length;
-  gint num_chars;
+  int offset;
+  int length;
+  int num_chars;
   PangoAnalysis analysis;
 };
 
diff --git a/pango/pango-layout.c b/pango/pango-layout.c
index ac396ba0..c721b41b 100644
--- a/pango/pango-layout.c
+++ b/pango/pango-layout.c
@@ -76,7 +76,7 @@
 #include "config.h"
 #include "pango-glyph.h"                /* For pango_shape() */
 #include "pango-break.h"
-#include "pango-item.h"
+#include "pango-item-private.h"
 #include "pango-engine.h"
 #include "pango-impl-utils.h"
 #include "pango-glyph-item.h"
@@ -5932,18 +5932,11 @@ justify_clusters (PangoLayoutLine *line,
 
           dir = run->item->analysis.level % 2 == 0 ? +1 : -1;
 
-          /* We need character offset of the start of the run.  We don't have this.
-           * Compute by counting from the beginning of the line.  The naming is
-           * confusing.  Note that:
-           *
-           * run->item->offset        is byte offset of start of run in layout->text.
-           * state->line_start_index  is byte offset of start of line in layout->text.
-           * state->line_start_offset is character offset of start of line in layout->text.
+          /* Note: we simply assert here, since our items are all internally
+           * created. If that ever changes, we need to add a fallback here.
            */
-          g_assert (run->item->offset >= state->line_start_index);
-          offset = state->line_start_offset
-                 + pango_utf8_strlen (text + state->line_start_index,
-                                      run->item->offset - state->line_start_index);
+          g_assert (run->item->analysis.flags & PANGO_ANALYSIS_FLAG_HAS_CHAR_OFFSET);
+          offset = ((PangoItemPrivate *)run->item)->char_offset;
 
           for (have_cluster = dir > 0 ?
                  pango_glyph_item_iter_init_start (&cluster_iter, run, text) :
@@ -6077,18 +6070,11 @@ justify_words (PangoLayoutLine *line,
           gboolean have_cluster;
           int offset;
 
-          /* We need character offset of the start of the run.  We don't have this.
-           * Compute by counting from the beginning of the line.  The naming is
-           * confusing.  Note that:
-           *
-           * run->item->offset        is byte offset of start of run in layout->text.
-           * state->line_start_index  is byte offset of start of line in layout->text.
-           * state->line_start_offset is character offset of start of line in layout->text.
+          /* Note: we simply assert here, since our items are all internally
+           * created. If that ever changes, we need to add a fallback here.
            */
-          g_assert (run->item->offset >= state->line_start_index);
-          offset = state->line_start_offset
-                 + pango_utf8_strlen (text + state->line_start_index,
-                                      run->item->offset - state->line_start_index);
+          g_assert (run->item->analysis.flags & PANGO_ANALYSIS_FLAG_HAS_CHAR_OFFSET);
+          offset = ((PangoItemPrivate *)run->item)->char_offset;
 
           for (have_cluster = pango_glyph_item_iter_init_start (&cluster_iter, run, text);
                have_cluster;