[gimp] app: fix AppStream tag localization.

[Jehan <jehanp src gnome org>]

commit 68cea846587f3ebe71cff746913b55359882a1ba
Author: Jehan <jehan girinstud io>
Date:   Fri Oct 23 00:24:16 2020 +0200

    app: fix AppStream tag localization.
    
    As AppStream docs says, <description> "tag should be translated
    by-paragraph" in upstream metadata, which is what we have always done
    (i.e. <_p> tags which becomes <p xml:lang="xy">).
    
    Unfortunately as_app_get_description() is optimized to work for
    Collection Metadata where the 'tag is translated "as a whole"' (again
    cf. specs) for faster parsing. So we were ending up with a text mixing
    the original and all localized texts.
    I have opened a bug report to appstream-glib:
    https://github.com/hughsie/appstream-glib/issues/381
    
    While waiting for this to be fixed (i.e. when the function will handle
    both cases accordingly to the metadata source), this code makes my own
    locale extraction (defaulting to original text which is assumed to be
    the previous same level tag with no xml:lang if no tag with the exact
    lang attribute was found).

 app/core/gimpextension.c | 102 +++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 95 insertions(+), 7 deletions(-)
---
diff --git a/app/core/gimpextension.c b/app/core/gimpextension.c
index dfc1674f55..60a80dbf05 100644
--- a/app/core/gimpextension.c
+++ b/app/core/gimpextension.c
@@ -75,6 +75,10 @@ typedef struct
   gboolean  numbered_list;
   gint      list_num;
   gboolean  unnumbered_list;
+
+  const gchar *lang;
+  GString     *original;
+  gint         foreign_level;
 } ParseState;
 
 
@@ -111,6 +115,9 @@ static void         appstream_text_characters      (GMarkupParseContext  *contex
                                                     gsize                 text_len,
                                                     gpointer              user_data,
                                                     GError              **error);
+static const gchar* gimp_extension_get_tag_lang    (const gchar         **attribute_names,
+                                                    const gchar         **attribute_values);
+
 
 G_DEFINE_TYPE_WITH_PRIVATE (GimpExtension, gimp_extension, GIMP_TYPE_OBJECT)
 
@@ -343,10 +350,13 @@ gimp_extension_get_markup_description (GimpExtension *extension)
   GError        *error  = NULL;
   ParseState     state;
 
-  state.level = 0;
-  state.text = g_string_new (NULL);
+  state.level           = 0;
+  state.foreign_level   = -1;
+  state.text            = g_string_new (NULL);
   state.numbered_list   = FALSE;
   state.unnumbered_list = FALSE;
+  state.lang            = g_getenv ("LANGUAGE");
+  state.original        = NULL;
 
   xml_parser  = gimp_xml_parser_new (&appstream_text_parser, &state);
   description = gimp_extension_get_description (extension);
@@ -356,6 +366,14 @@ gimp_extension_get_markup_description (GimpExtension *extension)
       g_printerr ("%s: %s\n", G_STRFUNC, error->message);
       g_error_free (error);
     }
+
+  /* Append possibly last original text without proper localization. */
+  if (state.original)
+    {
+      g_string_append (state.text, state.original->str);
+      g_string_free (state.original, TRUE);
+    }
+
   markup = g_string_free (state.text, FALSE);
   gimp_xml_parser_free (xml_parser);
 
@@ -880,10 +898,47 @@ appstream_text_start_element (GMarkupParseContext  *context,
                               gpointer              user_data,
                               GError              **error)
 {
-  ParseState *state = user_data;
+  ParseState  *state  = user_data;
+  GString     *output = state->text;
+  const gchar *tag_lang;
 
   state->level++;
 
+  if (state->foreign_level >= 0)
+    return;
+
+  tag_lang = gimp_extension_get_tag_lang (attribute_names, attribute_values);
+  if ((state->lang == NULL && tag_lang == NULL) ||
+      g_strcmp0 (tag_lang, state->lang) == 0)
+    {
+      /* Current tag is our current language. */
+      if (state->original)
+        g_string_free (state->original, TRUE);
+      state->original = NULL;
+
+      output = state->text;
+    }
+  else if (tag_lang == NULL)
+    {
+      /* Current tag is the original language (and we want a
+       * localization).
+       */
+      if (state->original)
+        {
+          g_string_append (state->text, state->original->str);
+          g_string_free (state->original, TRUE);
+        }
+      state->original = g_string_new (NULL);
+
+      output = state->original;
+    }
+  else
+    {
+      /* Current tag is an unrelated language */
+      state->foreign_level = state->level;
+      return;
+    }
+
   if ((state->numbered_list || state->unnumbered_list) &&
       (g_strcmp0 (element_name, "ul") == 0 ||
        g_strcmp0 (element_name, "ol") == 0))
@@ -904,10 +959,10 @@ appstream_text_start_element (GMarkupParseContext  *context,
     {
       state->list_num++;
       if (state->numbered_list)
-        g_string_append_printf (state->text, "\n %d. ",
+        g_string_append_printf (output, "\n %d. ",
                                 state->list_num);
       else if (state->unnumbered_list)
-        g_string_append (state->text, "\n * ");
+        g_string_append (output, "\n * ");
       else
         g_set_error (error, GIMP_ERROR, GIMP_FAILED,
                      _("<li> must be inside <ol> or <ul> tags."));
@@ -931,7 +986,13 @@ appstream_text_end_element (GMarkupParseContext  *context,
 
   if (g_strcmp0 (element_name, "p") == 0)
     {
-      g_string_append (state->text, "\n\n");
+      if (state->foreign_level < 0)
+        {
+          if (state->original)
+            g_string_append (state->original, "\n\n");
+          else
+            g_string_append (state->text, "\n\n");
+        }
     }
   else if (g_strcmp0 (element_name, "ul") == 0 ||
            g_strcmp0 (element_name, "ol") == 0)
@@ -939,6 +1000,9 @@ appstream_text_end_element (GMarkupParseContext  *context,
       state->numbered_list   = FALSE;
       state->unnumbered_list = FALSE;
     }
+
+  if (state->foreign_level > state->level)
+    state->foreign_level = -1;
 }
 
 static void
@@ -950,5 +1014,29 @@ appstream_text_characters (GMarkupParseContext  *context,
 {
   ParseState *state = user_data;
 
-  g_string_append (state->text, text);
+  if (state->foreign_level < 0)
+    {
+      if (state->original)
+        g_string_append (state->original, text);
+      else
+        g_string_append (state->text, text);
+    }
+}
+
+static const gchar *
+gimp_extension_get_tag_lang (const gchar **attribute_names,
+                             const gchar **attribute_values)
+{
+  while (*attribute_names)
+    {
+      if (! strcmp (*attribute_names, "xml:lang"))
+        {
+          return *attribute_values;
+        }
+
+      attribute_names++;
+      attribute_values++;
+    }
+
+  return NULL;
 }