[pango/fix-nested-attributes] Fix attr iterators with overlapping attributes

[Matthias Clasen <matthiasc src gnome org>]

commit 54b593ec3e7829583ce2fec3fe22dff512db07fb
Author: Matthias Clasen <mclasen redhat com>
Date:   Thu Sep 17 08:24:48 2020 -0400

    Fix attr iterators with overlapping attributes
    
    This broke when PangoAttrIterator was changed to
    use an array for the stack of current attributes, in
    dec6c0868ef2c36. We were not always walking the array
    in the right order. The first attribute to check is
    at the *end* of the array.
    
    This showed up as misrendering in epsilon_0 example
    in gtk3-demo's text view markup demo.
    
    Test included.

 pango/pango-attributes.c | 17 ++++-----
 tests/testattributes.c   | 89 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 95 insertions(+), 11 deletions(-)
---
diff --git a/pango/pango-attributes.c b/pango/pango-attributes.c
index 12942043..4f96135b 100644
--- a/pango/pango-attributes.c
+++ b/pango/pango-attributes.c
@@ -2003,7 +2003,7 @@ pango_attr_iterator_range (PangoAttrIterator *iterator,
 gboolean
 pango_attr_iterator_next (PangoAttrIterator *iterator)
 {
-  guint i;
+  int i;
 
   g_return_val_if_fail (iterator != NULL, FALSE);
 
@@ -2016,19 +2016,14 @@ pango_attr_iterator_next (PangoAttrIterator *iterator)
 
   if (iterator->attribute_stack)
     {
-      for (i = 0; i < iterator->attribute_stack->len; i++)
+      for (i = iterator->attribute_stack->len - 1; i>= 0; i--)
         {
           const PangoAttribute *attr = g_ptr_array_index (iterator->attribute_stack, i);
 
           if (attr->end_index == iterator->start_index)
-            {
-              g_ptr_array_remove_index (iterator->attribute_stack, i); /* Can't use index_fast :( */;
-              i--;
-            }
+            g_ptr_array_remove_index (iterator->attribute_stack, i); /* Can't use index_fast :( */
           else
-            {
-              iterator->end_index = MIN (iterator->end_index, attr->end_index);
-            }
+            iterator->end_index = MIN (iterator->end_index, attr->end_index);
         }
     }
 
@@ -2136,14 +2131,14 @@ PangoAttribute *
 pango_attr_iterator_get (PangoAttrIterator *iterator,
                         PangoAttrType      type)
 {
-  guint i;
+  int i;
 
   g_return_val_if_fail (iterator != NULL, NULL);
 
   if (!iterator->attribute_stack)
     return NULL;
 
-  for (i = 0; i < iterator->attribute_stack->len; i++)
+  for (i = iterator->attribute_stack->len - 1; i>= 0; i--)
     {
       PangoAttribute *attr = g_ptr_array_index (iterator->attribute_stack, i);
 
diff --git a/tests/testattributes.c b/tests/testattributes.c
index 8db42b4a..6131f38c 100644
--- a/tests/testattributes.c
+++ b/tests/testattributes.c
@@ -944,6 +944,94 @@ test_merge2 (void)
   pango_attr_list_unref (list);
 }
 
+/* This only prints rise, size and scale, which are the
+ * only relevant attributes in the test that uses this
+ * function.
+ */
+static void
+print_tags_for_attributes (PangoAttrIterator *iter,
+                           GString           *s)
+{
+  PangoAttribute *attr;
+
+  attr = pango_attr_iterator_get (iter, PANGO_ATTR_RISE);
+  if (attr)
+    g_string_append_printf (s, "[%d, %d]rise=%d\n",
+                            attr->start_index, attr->end_index,
+                            ((PangoAttrInt*)attr)->value);
+
+  attr = pango_attr_iterator_get (iter, PANGO_ATTR_SIZE);
+  if (attr)
+    g_string_append_printf (s, "[%d, %d]size=%d\n",
+                            attr->start_index, attr->end_index,
+                            ((PangoAttrInt*)attr)->value);
+
+  attr = pango_attr_iterator_get (iter, PANGO_ATTR_SCALE);
+  if (attr)
+    g_string_append_printf (s, "[%d, %d]scale=%f\n",
+                            attr->start_index, attr->end_index,
+                            ((PangoAttrFloat*)attr)->value);
+}
+
+static void
+test_iter_epsilon_zero (void)
+{
+  const char *markup = "𝜀<span rise=\"-6000\" size=\"x-small\" font_desc=\"italic\">0</span> = 𝜔<span 
rise=\"8000\" size=\"smaller\">𝜔<span rise=\"14000\" size=\"smaller\">𝜔<span rise=\"20000\">.<span 
rise=\"23000\">.<span rise=\"26000\">.</span></span></span></span></span>";
+  PangoAttrList *attributes;
+  PangoAttrIterator *attr;
+  char *text;
+  GError *error = NULL;
+  GString *s;
+
+  s = g_string_new ("");
+
+  pango_parse_markup (markup, -1, 0, &attributes, &text, NULL, &error);
+  g_assert_no_error (error);
+  g_assert_cmpstr (text, ==, "𝜀0 = 𝜔𝜔𝜔...");
+
+  attr = pango_attr_list_get_iterator (attributes);
+  do
+    {
+      int start, end;
+
+      pango_attr_iterator_range (attr, &start, &end);
+
+      g_string_append_printf (s, "range: [%d, %d]\n", start, end);
+
+      print_tags_for_attributes (attr, s);
+    }
+  while (pango_attr_iterator_next (attr));
+
+  g_assert_cmpstr (s->str, ==,
+                   "range: [0, 4]\n"
+                   "range: [4, 5]\n"
+                   "[4, 5]rise=-6000\n"
+                   "[4, 5]scale=0.694444\n"
+                   "range: [5, 12]\n"
+                   "range: [12, 16]\n"
+                   "[12, 23]rise=8000\n"
+                   "[12, 23]scale=0.833333\n"
+                   "range: [16, 20]\n"
+                   "[16, 23]rise=14000\n"
+                   "[16, 23]scale=0.694444\n"
+                   "range: [20, 21]\n"
+                   "[20, 23]rise=20000\n"
+                   "[16, 23]scale=0.694444\n"
+                   "range: [21, 22]\n"
+                   "[21, 23]rise=23000\n"
+                   "[16, 23]scale=0.694444\n"
+                   "range: [22, 23]\n"
+                   "[22, 23]rise=26000\n"
+                   "[16, 23]scale=0.694444\n"
+                   "range: [23, 2147483647]\n");
+
+  g_free (text);
+  pango_attr_list_unref (attributes);
+  pango_attr_iterator_destroy (attr);
+
+  g_string_free (s, TRUE);
+}
+
 int
 main (int argc, char *argv[])
 {
@@ -966,6 +1054,7 @@ main (int argc, char *argv[])
   g_test_add_func ("/attributes/iter/get", test_iter_get);
   g_test_add_func ("/attributes/iter/get_font", test_iter_get_font);
   g_test_add_func ("/attributes/iter/get_attrs", test_iter_get_attrs);
+  g_test_add_func ("/attributes/iter/epsilon_zero", test_iter_epsilon_zero);
 
   return g_test_run ();
 }