[evolution] Provide descriptive error message when an e-mail is not available in offline

[Milan Crha <mcrha src gnome org>]

commit a5513b3ea6ea52c4625edfd2b86eff9823c39e4c
Author: Milan Crha <mcrha redhat com>
Date:   Thu Nov 6 10:36:42 2014 +0100

    Provide descriptive error message when an e-mail is not available in offline

 mail/e-mail-reader.c |   16 ++++++++++++----
 mail/mail.error.xml  |    8 ++++++++
 2 files changed, 20 insertions(+), 4 deletions(-)
---
diff --git a/mail/e-mail-reader.c b/mail/e-mail-reader.c
index 202ec2d..033c2fb 100644
--- a/mail/e-mail-reader.c
+++ b/mail/e-mail-reader.c
@@ -2981,10 +2981,18 @@ exit:
                preview_pane = e_mail_reader_get_preview_pane (reader);
                web_view = e_preview_pane_get_web_view (preview_pane);
 
-               e_alert_submit (
-                       E_ALERT_SINK (web_view),
-                       "mail:no-retrieve-message",
-                       error->message, NULL);
+               if (g_error_matches (error, CAMEL_SERVICE_ERROR, CAMEL_SERVICE_ERROR_UNAVAILABLE) &&
+                   CAMEL_IS_OFFLINE_FOLDER (folder) &&
+                   camel_service_get_connection_status (CAMEL_SERVICE (camel_folder_get_parent_store 
(folder))) != CAMEL_SERVICE_CONNECTED)
+                       e_alert_submit (
+                               E_ALERT_SINK (web_view),
+                               "mail:no-retrieve-message-offline",
+                               NULL);
+               else
+                       e_alert_submit (
+                               E_ALERT_SINK (web_view),
+                               "mail:no-retrieve-message",
+                               error->message, NULL);
        }
 
        g_clear_error (&error);
diff --git a/mail/mail.error.xml b/mail/mail.error.xml
index c248a1a..7c1b51d 100644
--- a/mail/mail.error.xml
+++ b/mail/mail.error.xml
@@ -476,6 +476,14 @@ An mbox account will be created to preserve the old mbox folders. You can delete
     <_secondary xml:space="preserve">{0}</_secondary>
   </error>
 
+  <error id="no-retrieve-message-offline" type="warning">
+    <_primary>Message is not available in offline.</_primary>
+    <_secondary>This can be due to the message not being downloaded yet. The folder, or the account, can be 
marked
+for offline synchronization. Then, once the account is online again, use File-&gt;Download
+Messages for Offline Usage, when this folder is selected, to make sure that all the messages
+in the folder will be available in offline.</_secondary>
+  </error>
+
   <error id="folder-open" type="error">
     <_primary>Failed to open folder.</_primary>
     <_secondary>The reported error was &quot;{0}&quot;.</_secondary>