From c9ba8760deec4b2f5c245e9120d59b622b383ceb Mon Sep 17 00:00:00 2001
From: Volker Hilsheimer <volker.hilsheimer@qt.io>
Date: Tue, 15 Apr 2025 12:58:40 +0200
Subject: [PATCH] Widget effects DRY: replace manual pointer handling with
 unique_ptr

Instead of repeatedly resetting of the static pointers after (or before)
calling deleteLater(), use a unique_ptr with a custom deleter.

Since we use deleteLater(), nothing will happen if one of those widgets
does leak to the point where static objects are destroyed; we'd at most
call deleteLater() at this point, which won't do anything (if we enqueue
a DeferredDelete event at all, then it will never be processed).

Pick-to: 6.8
Task-number: QTBUG-135976
Change-Id: I36a4780093eafd064dcb1a72696c1d9b21483b77
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>
(cherry picked from commit b50a2761e735208eeb62042ecfaba7a76e580454)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 src/widgets/widgets/qeffects.cpp | 36 ++++++++++++++++----------------
 1 file changed, 18 insertions(+), 18 deletions(-)

diff --git a/src/widgets/widgets/qeffects.cpp b/src/widgets/widgets/qeffects.cpp
index 74ac24a2b0a..50c09ec4daf 100644
--- a/src/widgets/widgets/qeffects.cpp
+++ b/src/widgets/widgets/qeffects.cpp
@@ -19,6 +19,15 @@
 
 QT_BEGIN_NAMESPACE
 
+struct DeleteLater
+{
+    void operator()(QObject *o) const
+    {
+        if (o)
+            o->deleteLater();
+    }
+};
+
 /*
   Internal class QAlphaWidget.
 
@@ -58,7 +67,7 @@ private:
     QElapsedTimer checkTime;
 };
 
-static QAlphaWidget* q_blend = nullptr;
+static std::unique_ptr<QAlphaWidget, DeleteLater> q_blend;
 
 /*
   Constructs a QAlphaWidget.
@@ -227,8 +236,7 @@ void QAlphaWidget::render()
         anim.stop();
         qApp->removeEventFilter(this);
         widget->setWindowOpacity(1);
-        q_blend = 0;
-        deleteLater();
+        q_blend.reset();
     } else {
         widget->setWindowOpacity(alpha);
     }
@@ -248,8 +256,7 @@ void QAlphaWidget::render()
                 lower();
             }
         }
-        q_blend = nullptr;
-        deleteLater();
+        q_blend.reset();
     } else {
         alphaBlend();
         pm = QPixmap::fromImage(mixedImage);
@@ -341,7 +348,7 @@ private:
     QPixmap pm;
 };
 
-static QRollEffect* q_roll = nullptr;
+static std::unique_ptr<QRollEffect, DeleteLater> q_roll;
 
 /*
   Construct a QRollEffect widget.
@@ -513,8 +520,7 @@ void QRollEffect::scroll()
                 lower();
             }
         }
-        q_roll = nullptr;
-        deleteLater();
+        q_roll.reset();
     }
 }
 
@@ -524,10 +530,7 @@ void QRollEffect::scroll()
 */
 void qScrollEffect(QWidget* w, QEffects::DirFlags orient, int time)
 {
-    if (q_roll) {
-        q_roll->deleteLater();
-        q_roll = nullptr;
-    }
+    q_roll.reset();
 
     if (!w)
         return;
@@ -537,7 +540,7 @@ void qScrollEffect(QWidget* w, QEffects::DirFlags orient, int time)
     Qt::WindowFlags flags = Qt::ToolTip;
 
     // those can be popups - they would steal the focus, but are disabled
-    q_roll = new QRollEffect(w, flags, orient);
+    q_roll.reset(new QRollEffect(w, flags, orient));
     q_roll->run(time);
 }
 
@@ -546,10 +549,7 @@ void qScrollEffect(QWidget* w, QEffects::DirFlags orient, int time)
 */
 void qFadeEffect(QWidget* w, int time)
 {
-    if (q_blend) {
-        q_blend->deleteLater();
-        q_blend = nullptr;
-    }
+    q_blend.reset();
 
     if (!w)
         return;
@@ -560,7 +560,7 @@ void qFadeEffect(QWidget* w, int time)
     Qt::WindowFlags flags = Qt::ToolTip;
 
     // those can be popups - they would steal the focus, but are disabled
-    q_blend = new QAlphaWidget(w, flags);
+    q_blend.reset(new QAlphaWidget(w, flags));
 
     q_blend->run(time);
 }