[pango/pango2] linebreaker: Apply show flags to line separators

[Matthias Clasen <matthiasc src gnome org>]

commit ea6a2d9bb5a33c92c982151fb8737104710cbc93
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun Jul 3 10:44:19 2022 -0400

    linebreaker: Apply show flags to line separators
    
    We only want line separators at the line end
    to be visible when the show flags say so. This
    was not working before, because the shaping always
    marks LS as unknown glyph.

 pango2/pango-line-breaker.c | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)
---
diff --git a/pango2/pango-line-breaker.c b/pango2/pango-line-breaker.c
index 6f068a9f2..cd17968e9 100644
--- a/pango2/pango-line-breaker.c
+++ b/pango2/pango-line-breaker.c
@@ -16,7 +16,7 @@
 
 #include <hb-ot.h>
 
-#if 0
+#if 1
 # define DEBUG1(...) g_debug (__VA_ARGS__)
 #else
 # define DEBUG1(...) do { } while (0)
@@ -1700,6 +1700,23 @@ add_missing_hyphen (Pango2LineBreaker *self,
   line->hyphenated = (item->analysis.flags & PANGO2_ANALYSIS_FLAG_NEED_HYPHEN) != 0;
 }
 
+static Pango2ShowFlags
+find_show_flags (const Pango2Analysis *analysis)
+{
+  GSList *l;
+  Pango2ShowFlags flags = 0;
+
+  for (l = analysis->extra_attrs; l; l = l->next)
+    {
+      Pango2Attribute *attr = l->data;
+
+      if (attr->type == PANGO2_ATTR_SHOW)
+        flags |= attr->int_value;
+    }
+
+  return flags;
+}
+
 static void
 zero_line_final_space (Pango2LineBreaker *self,
                        Pango2Line        *line)
@@ -1720,8 +1737,13 @@ zero_line_final_space (Pango2LineBreaker *self,
 
   if (glyphs->glyphs[glyph].glyph == PANGO2_GET_UNKNOWN_GLYPH (0x2028))
     {
-      DEBUG1 ("zero final space: visible space");
-      return; /* this LS is visible */
+      Pango2ShowFlags show_flags = find_show_flags (&item->analysis);
+
+      if ((show_flags & PANGO2_SHOW_LINE_BREAKS) != 0)
+        {
+          DEBUG1 ("zero final space: visible LS");
+          return; /* this LS is visible */
+        }
     }
 
   /* if the final char of line forms a cluster, and it's