From 7eadca395996e29c020287a48700d4ce81080431 Mon Sep 17 00:00:00 2001
From: link2xt <link2xt@testrun.org>
Date: Sun, 30 Jan 2022 20:00:00 +0000
Subject: [PATCH] imap: do not synchronize Seen flags on unwatched folders

Synchronizing seen flags doubles the time required to scan all
folders. Delta Chat only marks messages as Seen on Inbox or DeltaChat,
so there is no need to check for Seen flag on other folders.
---
 CHANGELOG.md     |  2 ++
 src/imap.rs      |  3 ---
 src/scheduler.rs | 11 +++++++++++
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e5615201b..00417300b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,8 @@
 - remove direct dependency on `byteorder` crate #3031
 - make it possible to cancel message sending by removing the message #3034,
   this was previosuly removed in 1.71.0 #2939
+- synchronize Seen flags only on watched folders to speed up
+  folder scanning #3041
 
 ### Fixes
 - fix splitting off text from webxdc messages #3032
diff --git a/src/imap.rs b/src/imap.rs
index f68c10873..b36b448f8 100644
--- a/src/imap.rs
+++ b/src/imap.rs
@@ -464,9 +464,6 @@ impl Imap {
         self.delete_messages(context, watch_folder)
             .await
             .context("delete_messages")?;
-        self.sync_seen_flags(context, watch_folder)
-            .await
-            .context("sync_seen_flags")?;
 
         Ok(())
     }
diff --git a/src/scheduler.rs b/src/scheduler.rs
index 2cff9b7d5..fe1637a10 100644
--- a/src/scheduler.rs
+++ b/src/scheduler.rs
@@ -188,6 +188,17 @@ async fn fetch_idle(ctx: &Context, connection: &mut Imap, folder: Config) -> Int
                 return InterruptInfo::new(false);
             }
 
+            // Synchronize Seen flags.
+            if let Err(err) = connection
+                .sync_seen_flags(ctx, &watch_folder)
+                .await
+                .context("sync_seen_flags")
+            {
+                connection.trigger_reconnect(ctx).await;
+                warn!(ctx, "{:#}", err);
+                return InterruptInfo::new(false);
+            }
+
             connection.connectivity.set_connected(ctx).await;
 
             // idle