St: avoid blocking IO to resolve relative urls

realpath() does a series of lstat() on each path component to resolve
symbolic links, but we just want to get an absolute path, and we don't
really care if it is physical or not. Going through a GFile does the
canonicalization we need, and is a lot faster.

https://bugzilla.gnome.org/show_bug.cgi?id=687881

src/st/st-theme-node.c

@@ -1738,15 +1738,19 @@ _st_theme_node_ensure_background (StThemeNode *node)
               else if (term->type == TERM_URI)
                 {
                   CRStyleSheet *base_stylesheet;
+                  GFile *file;
 
                   if (decl->parent_statement != NULL)
                     base_stylesheet = decl->parent_statement->parent_sheet;
                   else
                     base_stylesheet = NULL;
 
-                  node->background_image = _st_theme_resolve_url (node->theme,
+                  file = _st_theme_resolve_url (node->theme,
                                                 base_stylesheet,
                                                 term->content.str->stryng->str);
+
+                  node->background_image = g_strdup (g_file_get_path (file));
+                  g_object_unref (file);
                 }
             }
         }
@@ -1843,6 +1847,7 @@ _st_theme_node_ensure_background (StThemeNode *node)
           if (decl->value->type == TERM_URI)
             {
               CRStyleSheet *base_stylesheet;
+              GFile *file;
 
               if (decl->parent_statement != NULL)
                 base_stylesheet = decl->parent_statement->parent_sheet;
@@ -1850,9 +1855,12 @@ _st_theme_node_ensure_background (StThemeNode *node)
                 base_stylesheet = NULL;
 
               g_free (node->background_image);
-              node->background_image = _st_theme_resolve_url (node->theme,
+              file = _st_theme_resolve_url (node->theme,
                                             base_stylesheet,
                                             decl->value->content.str->stryng->str);
+
+              node->background_image = g_strdup (g_file_get_path (file));
+              g_object_unref (file);
             }
           else if (term_is_inherit (decl->value))
             {
@@ -2668,6 +2676,7 @@ st_theme_node_get_border_image (StThemeNode *node)
           int border_bottom;
           int border_left;
 
+          GFile *file;
           char *filename;
 
           /* Support border-image: none; to suppress a previously specified border image */
@@ -2746,7 +2755,10 @@ st_theme_node_get_border_image (StThemeNode *node)
           else
             base_stylesheet = NULL;
 
-          filename = _st_theme_resolve_url (node->theme, base_stylesheet, url);
+          file = _st_theme_resolve_url (node->theme, base_stylesheet, url);
+          filename = g_strdup (g_file_get_path (file));
+          g_object_unref (file);
+
           if (filename == NULL)
             goto next_property;
 

src/st/st-theme-private.h

@@ -29,8 +29,8 @@ G_BEGIN_DECLS
 GPtrArray *_st_theme_get_matched_properties (StTheme       *theme,
                                              StThemeNode   *node);
 
-/* Resolve an URL from the stylesheet to a filename */
+/* Resolve an URL from the stylesheet to a file */
-char *_st_theme_resolve_url (StTheme      *theme,
+GFile *_st_theme_resolve_url (StTheme      *theme,
                               CRStyleSheet *base_stylesheet,
                               const char   *url);
 

src/st/st-theme.c

@@ -849,9 +849,16 @@ add_matched_properties (StTheme      *a_this,
                 char *filename = NULL;
 
                 if (import_rule->url->stryng && import_rule->url->stryng->str)
-                  filename = _st_theme_resolve_url (a_this,
+                  {
+                    GFile *file;
+
+                    file = _st_theme_resolve_url (a_this,
                                                   a_nodesheet,
                                                   import_rule->url->stryng->str);
+                    filename = g_strdup (g_file_get_path (file));
+
+                    g_object_unref (file);
+                  }
 
                 if (filename)
                   import_rule->sheet = parse_stylesheet (filename, NULL);
@@ -999,84 +1006,41 @@ _st_theme_get_matched_properties (StTheme        *theme,
  * local filename, if possible. The resolution here is distinctly lame and
  * will fail on many examples.
  */
-char *
+GFile *
 _st_theme_resolve_url (StTheme      *theme,
                        CRStyleSheet *base_stylesheet,
                        const char   *url)
 {
+  char *scheme;
+  GFile *stylesheet, *resource;
+
+  if ((scheme = g_uri_parse_scheme (url)))
+    {
+      g_free (scheme);
+      resource = g_file_new_for_uri (url);
+    }
+  else if (base_stylesheet != NULL)
+    {
       const char *base_filename = NULL;
       char *dirname;
-  char *filename;
-  char *canonicalized_path;
-
-  /* Handle absolute file:/ URLs */
-  if (g_str_has_prefix (url, "file:") ||
-      g_str_has_prefix (url, "File:") ||
-      g_str_has_prefix (url, "FILE:"))
-    {
-      GError *error = NULL;
-      char *filename;
-
-      filename = g_filename_from_uri (url, NULL, &error);
-      if (filename == NULL)
-        {
-          g_warning ("%s", error->message);
-          g_error_free (error);
-        }
-
-      return filename;
-    }
-
-  /* Guard against http:/ URLs */
-
-  if (g_str_has_prefix (url, "http:") ||
-      g_str_has_prefix (url, "Http:") ||
-      g_str_has_prefix (url, "HTTP:"))
-    {
-      g_warning ("Http URL '%s' in theme stylesheet is not supported", url);
-      return NULL;
-    }
-
-  /* Assume anything else is a relative URL, and "resolve" it
-   */
-  if (url[0] == '/')
-    {
-      canonicalized_path = realpath (url, NULL);
-      if (g_mem_is_system_malloc ())
-        {
-          filename = canonicalized_path;
-        }
-      else
-        {
-          filename = g_strdup (canonicalized_path);
-          free (canonicalized_path);
-        }
-      return filename;
-    }
 
       base_filename = g_hash_table_lookup (theme->filenames_by_stylesheet, base_stylesheet);
 
-  if (base_filename == NULL)
+      /* This is an internal function, if we get here with
-    {
+         a bad @base_stylesheet we have a problem. */
-      g_warning ("Can't get base to resolve url '%s'", url);
+      g_assert (base_filename);
-      return NULL;
-    }
 
       dirname = g_path_get_dirname (base_filename);
-  filename = g_build_filename (dirname, url, NULL);
+      stylesheet = g_file_new_for_path (dirname);
-  canonicalized_path = realpath (filename, NULL);
+      resource = g_file_resolve_relative_path (stylesheet, url);
-  g_free (dirname);
-  g_free (filename);
 
-  if (g_mem_is_system_malloc ())
+      g_object_unref (stylesheet);
-    {
+      g_free (dirname);
-      filename = canonicalized_path;
     }
   else
     {
-      filename = g_strdup (canonicalized_path);
+      resource = g_file_new_for_path (url);
-      free (canonicalized_path);
     }
 
-  return filename;
+  return resource;
 }