[geary/wip/conversation-polish: 4/22] Display loading indicator for long-running local ConversationEmail loads

[Michael Gratton <mjog src gnome org>]

commit 46ebfa38df690e77f0140349839ccb235ece93c1
Author: Michael Gratton <mike vee net>
Date:   Wed Jan 23 16:09:23 2019 +1100

    Display loading indicator for long-running local ConversationEmail loads
    
    Even though it's a local load, ConversationEmail's initial mody load can
    take some time if its EmailStore or target folder's replay queue is
    busy, as is the case at application start up at least.

 src/client/conversation-viewer/conversation-email.vala | 12 ++++++++++++
 1 file changed, 12 insertions(+)
---
diff --git a/src/client/conversation-viewer/conversation-email.vala 
b/src/client/conversation-viewer/conversation-email.vala
index 41df0869..1593c19c 100644
--- a/src/client/conversation-viewer/conversation-email.vala
+++ b/src/client/conversation-viewer/conversation-email.vala
@@ -37,6 +37,9 @@ public class ConversationEmail : Gtk.Box, Geary.BaseInterface {
         Geary.Email.REQUIRED_FOR_MESSAGE
     );
 
+    // Time to wait loading the body before showing the progress meter
+    private const int BODY_LOAD_TIMEOUT_MSEC = 250;
+
 
     /**
      * Iterator that returns all message views in an email view.
@@ -299,6 +302,9 @@ public class ConversationEmail : Gtk.Box, Geary.BaseInterface {
 
     private Configuration config;
 
+    private Geary.TimeoutManager body_loading_timeout;
+
+
     /** Determines if all message's web views have finished loading. */
     private Geary.Nonblocking.Spinlock message_bodies_loaded_lock =
         new Geary.Nonblocking.Spinlock();
@@ -523,6 +529,10 @@ public class ConversationEmail : Gtk.Box, Geary.BaseInterface {
 
         this.primary_message.infobars.add(this.not_saved_infobar);
 
+        this.body_loading_timeout = new Geary.TimeoutManager.milliseconds(
+            BODY_LOAD_TIMEOUT_MSEC, this.primary_message.start_progress_pulse
+        );
+
         pack_start(this.primary_message, true, true, 0);
         update_email_state();
     }
@@ -564,6 +574,7 @@ public class ConversationEmail : Gtk.Box, Geary.BaseInterface {
 
         bool loaded = this.email.fields.fulfills(REQUIRED_FOR_LOAD);
         if (!loaded) {
+            this.body_loading_timeout.start();
             try {
                 this.email = yield this.email_store.fetch_email_async(
                     this.email.id,
@@ -577,6 +588,7 @@ public class ConversationEmail : Gtk.Box, Geary.BaseInterface {
                 // download it in the background.
                 this.fetch_body_remote.begin();
             }
+            this.body_loading_timeout.reset();
         }
 
         if (loaded) {