From 82c40f18709484fd462643aa113a8ccf961b646a Mon Sep 17 00:00:00 2001
From: Felix Ernst <fe.a.ernst@gmail.com>
Date: Tue, 26 Oct 2021 17:28:09 +0200
Subject: [PATCH] Fix hamburger menu opening as a window on Wayland

Before this commit, if an app window is unfocused and the first
click on the window is the hamburger menu button, the menu would
appear displaced as a separate window on Wayland.

This commit fixes this by setting a sane transientParent for the
menu. This is slightly difficult because there can be any number
of hamburger buttons in any number of different windows so we need
to figure out spontaneously which button was pressed to open the
menu.

BUG: 442375
---
 src/khamburgermenuhelpers.cpp | 26 ++++++++++++++++++++++++--
 src/khamburgermenuhelpers_p.h |  2 +-
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/src/khamburgermenuhelpers.cpp b/src/khamburgermenuhelpers.cpp
index 88242aa5..d1ae2835 100644
--- a/src/khamburgermenuhelpers.cpp
+++ b/src/khamburgermenuhelpers.cpp
@@ -10,7 +10,10 @@
 #include "khamburgermenu.h"
 
 #include <QEvent>
+#include <QMenu>
+#include <QToolButton>
 #include <QWidget>
+#include <QWindow>
 
 ListenerContainer::ListenerContainer(KHamburgerMenuPrivate *hamburgerMenuPrivate)
     : QObject{hamburgerMenuPrivate},
@@ -28,13 +31,32 @@ bool AddOrRemoveActionListener::eventFilter(QObject * /*watched*/, QEvent *event
     return false;
 }
 
-bool ButtonPressListener::eventFilter(QObject * /*watched*/, QEvent *event)
+bool ButtonPressListener::eventFilter(QObject *watched, QEvent *event)
 {
     if (event->type() == QEvent::KeyPress || event->type() == QEvent::MouseButtonPress) {
         auto hamburgerMenuPrivate = static_cast<KHamburgerMenuPrivate *>(parent());
         auto q = static_cast<KHamburgerMenu *>(hamburgerMenuPrivate->q_ptr);
         Q_EMIT q->aboutToShowMenu();
-        hamburgerMenuPrivate->resetMenu();
+        hamburgerMenuPrivate->resetMenu(); // This menu never has a parent which can be
+        // problematic because it can lead to situations in which the QMenu itself is
+        // treated like its own window.
+        // To avoid this we set a sane transientParent() now even if it already has one
+        // because the menu might be opened from another window this time.
+        const auto watchedButton = qobject_cast<QToolButton *>(watched);
+        if (!watchedButton) {
+            return false;
+        }
+        auto menu = watchedButton->menu();
+        if (!menu) {
+            return false;
+        }
+        menu->winId(); // trigger being a native widget already, to ensure windowHandle created
+        // generic code if not known if the available parent widget is a native widget or not
+        auto parentWindowHandle = watchedButton->windowHandle();
+        if (!parentWindowHandle) {
+            parentWindowHandle = watchedButton->nativeParentWidget()->windowHandle();
+        }
+        menu->windowHandle()->setTransientParent(parentWindowHandle);
     }
     return false;
 }
diff --git a/src/khamburgermenuhelpers_p.h b/src/khamburgermenuhelpers_p.h
index f0d98790..4993ee61 100644
--- a/src/khamburgermenuhelpers_p.h
+++ b/src/khamburgermenuhelpers_p.h
@@ -80,7 +80,7 @@ class ButtonPressListener : public QObject
 protected:
     inline ButtonPressListener(QObject *parent) : QObject{parent} {   };
 
-    bool eventFilter(QObject * /*watched*/, QEvent *event) override;
+    bool eventFilter(QObject *watched, QEvent *event) override;
 
     friend class ListenerContainer;
 };
-- 
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