[geary] Don't launch multiple list ops when changing folders: Bug #712977

[Jim Nelson <jnelson src gnome org>]

commit cec8b3f350c34da8c104ce25de9578a631ad3ec1
Author: Jim Nelson <jim yorba org>
Date:   Wed Jan 21 16:30:25 2015 -0800

    Don't launch multiple list ops when changing folders: Bug #712977
    
    Clearing the ConversationListStore caused multiple selection-changed
    notifications to the ConversationListView, whose signals in turn
    caused I/O in the GearyController.  This stops that process in its
    tracks.

 .../conversation-list/conversation-list-store.vala |    5 +++++
 .../conversation-list/conversation-list-view.vala  |   13 +++++++++++++
 2 files changed, 18 insertions(+), 0 deletions(-)
---
diff --git a/src/client/conversation-list/conversation-list-store.vala 
b/src/client/conversation-list/conversation-list-store.vala
index 2444f7c..179937b 100644
--- a/src/client/conversation-list/conversation-list-store.vala
+++ b/src/client/conversation-list/conversation-list-store.vala
@@ -38,6 +38,7 @@ public class ConversationListStore : Gtk.ListStore {
     public string? account_owner_email { get; set; default = null; }
     public Geary.ProgressMonitor preview_monitor { get; private set; default = 
         new Geary.SimpleProgressMonitor(Geary.ProgressType.ACTIVITY); }
+    public bool is_clearing { get; private set; default = false; }
     
     private Geary.App.ConversationMonitor conversation_monitor;
     private Geary.Folder? current_folder = null;
@@ -70,6 +71,8 @@ public class ConversationListStore : Gtk.ListStore {
     }
     
     private void on_conversation_monitor_changed() {
+        is_clearing = true;
+        
         if (conversation_monitor != null) {
             conversation_monitor.scan_completed.disconnect(on_scan_completed);
             conversation_monitor.conversations_added.disconnect(on_conversations_added);
@@ -93,6 +96,8 @@ public class ConversationListStore : Gtk.ListStore {
             conversation_monitor.conversation_trimmed.connect(on_conversation_trimmed);
             conversation_monitor.email_flags_changed.connect(on_email_flags_changed);
         }
+        
+        is_clearing = false;
     }
     
     public void set_current_folder(Geary.Folder? current_folder, Cancellable? cancellable_folder) {
diff --git a/src/client/conversation-list/conversation-list-view.vala 
b/src/client/conversation-list/conversation-list-view.vala
index bdc1370..08cf5f1 100644
--- a/src/client/conversation-list/conversation-list-view.vala
+++ b/src/client/conversation-list/conversation-list-view.vala
@@ -314,6 +314,19 @@ public class ConversationListView : Gtk.TreeView {
     // Gtk.TreeSelection can fire its "changed" signal even when nothing's changed, so look for that
     // and prevent to avoid subscribers from doing the same things multiple times
     private void on_selection_changed() {
+        // if the ConversationListStore is clearing, then this is called repeatedly as the elements
+        // are removed, causing signals to fire and a flurry of I/O that is immediately cancelled
+        // this prevents that, merely firing the signal once to indicate all selections are
+        // dropped while clearing
+        if (conversation_list_store.is_clearing) {
+            if (selected.size > 0) {
+                selected.clear();
+                conversations_selected(selected.read_only_view);
+            }
+            
+            return;
+        }
+        
         List<Gtk.TreePath> paths = get_all_selected_paths();
         if (paths.length() == 0) {
             // only notify if this is different than what was previously reported