[geary] Shift special folder priorities when synchronizing account

[Jim Nelson <jnelson src gnome org>]

commit ab310a3702eb99524b93cbaa97373b603ffdbe1a
Author: Jim Nelson <jim yorba org>
Date:   Fri Jul 18 16:21:15 2014 -0700

    Shift special folder priorities when synchronizing account
    
    This patch solves two issues: (a) sometimes messages stick around in
    conversations too long because Geary hasn't synchronized with Trash
    (therefore realizing they should be blacklisted), and (b) All Mail can
    take a long time to synchronize because of its bulk size.
    
    This patch moves Trash (and Sent Mail) higher up in priority and moves
    All Mail and Archive down to reflect these issues.

 .../imap-engine-account-synchronizer.vala          |   29 +++++++++++++------
 1 files changed, 20 insertions(+), 9 deletions(-)
---
diff --git a/src/engine/imap-engine/imap-engine-account-synchronizer.vala 
b/src/engine/imap-engine/imap-engine-account-synchronizer.vala
index 071cc72..5b8ef8b 100644
--- a/src/engine/imap-engine/imap-engine-account-synchronizer.vala
+++ b/src/engine/imap-engine/imap-engine-account-synchronizer.vala
@@ -175,8 +175,7 @@ private class Geary.ImapEngine.AccountSynchronizer : Geary.BaseObject {
     }
     
     // This is used to ensure that certain special folders get prioritized over others, so folders
-    // important to the user (i.e. Inbox) and folders handy for pulling all mail (i.e. All Mail) go
-    // first while less-used folders (Trash, Spam) are fetched last
+    // important to the user (i.e. Inbox) go first while less-used folders (Spam) are fetched last
     private static int bg_queue_comparator(MinimalFolder a, MinimalFolder b) {
         if (a == b)
             return 0;
@@ -190,9 +189,24 @@ private class Geary.ImapEngine.AccountSynchronizer : Geary.BaseObject {
     }
     
     // Lower the score, the higher the importance.
+    //
+    // Some explanation is due here.  It may seem odd to place TRASH, SENT, and DRAFTS so high, but
+    // there's a method to the madness.  In particular, because Geary can produce a lot of drafts
+    // during composition, it's important to synchronize with Trash so discarded drafts don't wind
+    // up included in conversations until, eventually, the Trash is synchronized.  (Recall that
+    // Spam and Trash are blacklisted in conversations and searching.)  Since Drafts is open while
+    // writing them, it's not vital to keep it absolutely high, but Trash is usually not open,
+    // so it should be.
+    //
+    // All Mail is important, but synchronizing with it can be hard on the system because of the
+    // sheer amount of messages, and so it's placed lower to put it off until the more active
+    // folders are finished.
     private static int score_folder(Folder a) {
         switch (a.special_folder_type) {
             case SpecialFolderType.INBOX:
+                return -70;
+            
+            case SpecialFolderType.TRASH:
                 return -60;
             
             case SpecialFolderType.SENT:
@@ -201,22 +215,19 @@ private class Geary.ImapEngine.AccountSynchronizer : Geary.BaseObject {
             case SpecialFolderType.DRAFTS:
                 return -40;
             
-            case SpecialFolderType.ALL_MAIL:
-            case SpecialFolderType.ARCHIVE:
+            case SpecialFolderType.FLAGGED:
                 return -30;
             
-            case SpecialFolderType.FLAGGED:
+            case SpecialFolderType.IMPORTANT:
                 return -20;
             
-            case SpecialFolderType.IMPORTANT:
+            case SpecialFolderType.ALL_MAIL:
+            case SpecialFolderType.ARCHIVE:
                 return -10;
             
             case SpecialFolderType.SPAM:
                 return 10;
             
-            case SpecialFolderType.TRASH:
-                return 20;
-            
             default:
                 return 0;
         }