[geary/cherry-pick-99730af3] Merge branch 'mjog/766-search-deadlock' into 'mainline'

[Michael Gratton <mjog src gnome org>]

commit 9fa35a4442188f8471b026b721fbf6a7bbfcd7e9
Author: Michael Gratton <mike vee net>
Date:   Sat Apr 4 02:27:12 2020 +0000

    Merge branch 'mjog/766-search-deadlock' into 'mainline'
    
    ConversationWebView: Avoid a deadlock cancelling search highlighting
    
    Closes #766
    
    See merge request GNOME/geary!486
    
    (cherry picked from commit 99730af3cea7f2ba0dbe8aa33636672843a06e69)
    
    ee2c66a3 ConversationWebView: Avoid a deadlock cancelling search highlighting

 src/client/conversation-viewer/conversation-web-view.vala | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
---
diff --git a/src/client/conversation-viewer/conversation-web-view.vala 
b/src/client/conversation-viewer/conversation-web-view.vala
index d22a836e..9832efa5 100644
--- a/src/client/conversation-viewer/conversation-web-view.vala
+++ b/src/client/conversation-viewer/conversation-web-view.vala
@@ -128,7 +128,10 @@ public class ConversationWebView : ClientWebView {
                 callback();
             });
         ulong cancelled_handler = cancellable.cancelled.connect(() => {
-                callback();
+                // Do this at idle since per the docs for
+                // GLib.Cancellable.disconnect, disconnecting a
+                // handler from within a handler causes a deadlock.
+                GLib.Idle.add(() => callback());
             });
 
         controller.search(