From 296ede3aab2c0cc1acd28a2adb3017ac74d7ed6b Mon Sep 17 00:00:00 2001
From: Marc Mutz <marc.mutz@qt.io>
Date: Tue, 13 Feb 2024 14:24:22 +0100
Subject: [PATCH] QGuiApplication: replace a QSet with QMinimalVarLengthFlatSet

The number of windows in a windowing system is clearly small, even
smaller the number of windows that should be affected by a single
touch event, so QSet is overkill. Use the recently-added
QMinimalVarLengthFlatSet instead, backed by a QVLA<16>. Even though
insertion and lookup are now logarithmic instead of constant-time, the
saved memory allocations will make up for it.

Change-Id: Ie33ecf4a155e58db597c67ed9c78549255c48b99
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
---
 src/gui/kernel/qguiapplication.cpp | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/gui/kernel/qguiapplication.cpp b/src/gui/kernel/qguiapplication.cpp
index d8977a5e90e..e86b94ac4d5 100644
--- a/src/gui/kernel/qguiapplication.cpp
+++ b/src/gui/kernel/qguiapplication.cpp
@@ -25,6 +25,7 @@
 #include <QtCore/QVariant>
 #include <QtCore/private/qcoreapplication_p.h>
 #include <QtCore/private/qabstracteventdispatcher_p.h>
+#include <QtCore/private/qminimalflatset_p.h>
 #include <QtCore/qmutex.h>
 #include <QtCore/private/qthread_p.h>
 #include <QtCore/private/qlocking_p.h>
@@ -2931,17 +2932,16 @@ void QGuiApplicationPrivate::processTouchEvent(QWindowSystemInterfacePrivate::To
         // Send the TouchCancel to all windows with active touches and clean up.
         QTouchEvent touchEvent(QEvent::TouchCancel, device, e->modifiers);
         touchEvent.setTimestamp(e->timestamp);
-        QSet<QWindow *> windowsNeedingCancel;
+        QMinimalVarLengthFlatSet<QWindow *, 16> windowsNeedingCancel;
 
         for (auto &epd : devPriv->activePoints.values()) {
             if (QWindow *w = QMutableEventPoint::window(epd.eventPoint))
                 windowsNeedingCancel.insert(w);
         }
 
-        for (QSet<QWindow *>::const_iterator winIt = windowsNeedingCancel.constBegin(),
-            winItEnd = windowsNeedingCancel.constEnd(); winIt != winItEnd; ++winIt) {
-            QGuiApplication::sendSpontaneousEvent(*winIt, &touchEvent);
-        }
+        for (QWindow *w : windowsNeedingCancel)
+            QGuiApplication::sendSpontaneousEvent(w, &touchEvent);
+
         if (!self->synthesizedMousePoints.isEmpty() && !e->synthetic()) {
             for (QHash<QWindow *, SynthesizedMouseData>::const_iterator synthIt = self->synthesizedMousePoints.constBegin(),
                  synthItEnd = self->synthesizedMousePoints.constEnd(); synthIt != synthItEnd; ++synthIt) {