[evolution] Add e_mail_part_id_has_substr().

[Matthew Barnes <mbarnes src gnome org>]

commit 5ad0b6d8f7ee9244eb328b5951b98f8945e7b3cf
Author: Matthew Barnes <mbarnes redhat com>
Date:   Sat May 18 11:10:22 2013 -0400

    Add e_mail_part_id_has_substr().

 em-format/e-mail-part.h                            |    2 ++
 .../e-mail-display-popup-prefer-plain.c            |    3 ++-
 modules/prefer-plain/e-mail-parser-prefer-plain.c  |    2 +-
 3 files changed, 5 insertions(+), 2 deletions(-)
---
diff --git a/em-format/e-mail-part.h b/em-format/e-mail-part.h
index 769d5bb..c67cb83 100644
--- a/em-format/e-mail-part.h
+++ b/em-format/e-mail-part.h
@@ -103,6 +103,8 @@ gboolean    e_mail_part_id_has_prefix       (EMailPart *part,
                                                 const gchar *prefix);
 gboolean       e_mail_part_id_has_suffix       (EMailPart *part,
                                                 const gchar *suffix);
+gboolean       e_mail_part_id_has_substr       (EMailPart *part,
+                                                const gchar *substr);
 void           e_mail_part_update_validity     (EMailPart *part,
                                                 CamelCipherValidity *validity,
                                                 guint32 validity_type);
diff --git a/modules/prefer-plain/e-mail-display-popup-prefer-plain.c 
b/modules/prefer-plain/e-mail-display-popup-prefer-plain.c
index 3935263..91df97c 100644
--- a/modules/prefer-plain/e-mail-display-popup-prefer-plain.c
+++ b/modules/prefer-plain/e-mail-display-popup-prefer-plain.c
@@ -315,7 +315,8 @@ mail_display_popup_prefer_plain_update_actions (EMailDisplayPopupExtension *exte
                EMailPart *p = link->data;
 
                if (e_mail_part_id_has_prefix (p, prefix) &&
-                   (strstr (p->id, "text_html") || strstr (p->id, "plain_text"))) {
+                   (e_mail_part_id_has_substr (p, "text_html") ||
+                    e_mail_part_id_has_substr (p, "plain_text"))) {
                        const gchar *p_id;
 
                        p_id = e_mail_part_get_id (p);
diff --git a/modules/prefer-plain/e-mail-parser-prefer-plain.c 
b/modules/prefer-plain/e-mail-parser-prefer-plain.c
index 8282b02..c09c70d 100644
--- a/modules/prefer-plain/e-mail-parser-prefer-plain.c
+++ b/modules/prefer-plain/e-mail-parser-prefer-plain.c
@@ -275,7 +275,7 @@ empe_prefer_plain_parse (EMailParserExtension *extension,
                        for (link = head; link != NULL; link = g_list_next (link)) {
                                EMailPart *mail_part = link->data;
 
-                               if (strstr (mail_part->id, ".text_html") != NULL) {
+                               if (e_mail_part_id_has_substr (mail_part, ".text_html")) {
                                        has_html = TRUE;
                                        break;
                                }