From 9ff1d7f8140de1224bb37fba0cb266a58f37e66d Mon Sep 17 00:00:00 2001
From: David Tardon <dtardon@redhat.com>
Date: Thu, 5 May 2016 15:53:06 +0200
Subject: [PATCH] improve perf. of VCL event dispatch

Anectodal evidence: for removal of 32 slides from 64 slide presentation,
time spent in Window::CallEventListeners has been cut down from 70% to
19% of the total time.

Change-Id: Ic8fbb44fa935f068e1b18235592dec0d7e71aec7
---
 vcl/inc/window.h             |  2 ++
 vcl/source/window/event.cxx  | 13 ++++++++++++-
 vcl/source/window/window.cxx |  1 +
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/vcl/inc/window.h b/vcl/inc/window.h
index e06a6b1..302e9d0 100644
--- a/vcl/inc/window.h
+++ b/vcl/inc/window.h
@@ -201,6 +201,8 @@ public:
     VclPtr<vcl::Window> mpLastFocusWindow;
     VclPtr<vcl::Window> mpDlgCtrlDownWindow;
     std::vector<Link<VclWindowEvent&,void>> maEventListeners;
+    int mnEventListenersIteratingCount;
+    std::set<Link<VclWindowEvent&,void>> maEventListenersDeleted;
     std::vector<Link<VclWindowEvent&,void>> maChildEventListeners;
     int mnChildEventListenersIteratingCount;
     std::set<Link<VclWindowEvent&,void>> maChildEventListenersDeleted;
diff --git a/vcl/source/window/event.cxx b/vcl/source/window/event.cxx
index cb39104..68e822b 100644
--- a/vcl/source/window/event.cxx
+++ b/vcl/source/window/event.cxx
@@ -216,11 +216,22 @@ void Window::CallEventListeners( sal_uLong nEvent, void* pData )
     {
         // Copy the list, because this can be destroyed when calling a Link...
         std::vector<Link<VclWindowEvent&,void>> aCopy( mpWindowImpl->maEventListeners );
+        // we use an iterating counter/flag and a set of deleted Link's to avoid O(n^2) behaviour
+        mpWindowImpl->mnEventListenersIteratingCount++;
+        auto& rWindowImpl = *mpWindowImpl;
+        comphelper::ScopeGuard aGuard(
+            [&rWindowImpl]()
+            {
+                rWindowImpl.mnEventListenersIteratingCount--;
+                if (rWindowImpl.mnEventListenersIteratingCount == 0)
+                    rWindowImpl.maEventListenersDeleted.clear();
+            }
+        );
         for ( Link<VclWindowEvent&,void>& rLink : aCopy )
         {
             if (xWindow->IsDisposed()) break;
             // check this hasn't been removed in some re-enterancy scenario fdo#47368
-            if( std::find(mpWindowImpl->maEventListeners.begin(), mpWindowImpl->maEventListeners.end(), rLink) != mpWindowImpl->maEventListeners.end() )
+            if( rWindowImpl.maEventListenersDeleted.find(rLink) == rWindowImpl.maEventListenersDeleted.end() )
                 rLink.Call( aEvent );
         }
     }
diff --git a/vcl/source/window/window.cxx b/vcl/source/window/window.cxx
index f245c47..d1c1ffe 100644
--- a/vcl/source/window/window.cxx
+++ b/vcl/source/window/window.cxx
@@ -615,6 +615,7 @@ WindowImpl::WindowImpl( WindowType nType )
     mpNextOverlap                       = nullptr;                      // next overlap window of frame
     mpLastFocusWindow                   = nullptr;                      // window for focus restore
     mpDlgCtrlDownWindow                 = nullptr;                      // window for dialog control
+    mnEventListenersIteratingCount = 0;
     mnChildEventListenersIteratingCount = 0;
     mpUserData                          = nullptr;                      // user data
     mpCursor                            = nullptr;                      // cursor
-- 
2.7.4