[qpa] Prevent crash due to Surface getting null

Summary:
This is a regression due to changes in Breeze to support Qt 5.8+ behavior
change. KWin's own QPA operates like < Qt 5.7 and breeze was programmed
against that. Due to that it can happen now that Breeze hits code paths
in which KWin does not have a surface.

To trigger one only needed to open the user actions menu twice.

This change adds a test case which simulates the problem and fixes all
crashes happening in the code path.

Most likely shadows are now broken for KWin's own windows, this change is
only to prevent the crash and thus is for 5.10 branch, while shadow
fixing will go to master branch.

BUG: 382063
FIXED-IN: 5.10.4

Test Plan: New test case

Reviewers: #kwin, #plasma

Subscribers: plasma-devel, kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D6533

autotests/integration/CMakeLists.txt

@@ -45,6 +45,7 @@ integrationTest(NAME testPointerConstraints SRCS pointer_constraints_test.cpp)
 integrationTest(NAME testKeyboardLayout SRCS keyboard_layout_test.cpp)
 integrationTest(NAME testKeymapCreationFailure SRCS keymap_creation_failure_test.cpp)
 integrationTest(NAME testShowingDesktop SRCS showing_desktop_test.cpp)
+integrationTest(NAME testDontCrashUseractionsMenu SRCS dont_crash_useractions_menu.cpp)
 
 if (XCB_ICCCM_FOUND)
     integrationTest(NAME testMoveResize SRCS move_resize_window_test.cpp LIBS XCB::ICCCM)

autotests/integration/dont_crash_useractions_menu.cpp

@@ -0,0 +1,114 @@
+/********************************************************************
+KWin - the KDE window manager
+This file is part of the KDE project.
+
+Copyright (C) 2017 Martin Flöser <mgraesslin@kde.org>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*********************************************************************/
+#include "kwin_wayland_test.h"
+#include "cursor.h"
+#include "keyboard_input.h"
+#include "platform.h"
+#include "pointer_input.h"
+#include "shell_client.h"
+#include "screens.h"
+#include "useractions.h"
+#include "wayland_server.h"
+#include "workspace.h"
+
+#include <KWayland/Client/compositor.h>
+#include <KWayland/Client/keyboard.h>
+#include <KWayland/Client/pointer.h>
+#include <KWayland/Client/shell.h>
+#include <KWayland/Client/seat.h>
+#include <KWayland/Client/shm_pool.h>
+#include <KWayland/Client/surface.h>
+#include <KWayland/Client/touch.h>
+
+#include <linux/input.h>
+
+using namespace KWin;
+using namespace KWayland::Client;
+
+static const QString s_socketName = QStringLiteral("wayland_test_kwin_dont_crash_useractions_menu-0");
+
+class TestDontCrashUseractionsMenu : public QObject
+{
+    Q_OBJECT
+private Q_SLOTS:
+    void initTestCase();
+    void init();
+    void cleanup();
+
+    void testShowHideShowUseractionsMenu();
+};
+
+void TestDontCrashUseractionsMenu::initTestCase()
+{
+    qRegisterMetaType<KWin::ShellClient*>();
+    qRegisterMetaType<KWin::AbstractClient*>();
+    QSignalSpy workspaceCreatedSpy(kwinApp(), &Application::workspaceCreated);
+    QVERIFY(workspaceCreatedSpy.isValid());
+    kwinApp()->platform()->setInitialWindowSize(QSize(1280, 1024));
+    QMetaObject::invokeMethod(kwinApp()->platform(), "setOutputCount", Qt::DirectConnection, Q_ARG(int, 2));
+    QVERIFY(waylandServer()->init(s_socketName.toLocal8Bit()));
+
+    kwinApp()->start();
+    QVERIFY(workspaceCreatedSpy.wait());
+    QCOMPARE(screens()->count(), 2);
+    QCOMPARE(screens()->geometry(0), QRect(0, 0, 1280, 1024));
+    QCOMPARE(screens()->geometry(1), QRect(1280, 0, 1280, 1024));
+    waylandServer()->initWorkspace();
+}
+
+void TestDontCrashUseractionsMenu::init()
+{
+    QVERIFY(Test::setupWaylandConnection());
+
+    screens()->setCurrent(0);
+    KWin::Cursor::setPos(QPoint(1280, 512));
+}
+
+void TestDontCrashUseractionsMenu::cleanup()
+{
+    Test::destroyWaylandConnection();
+}
+
+void TestDontCrashUseractionsMenu::testShowHideShowUseractionsMenu()
+{
+    // this test creates the condition of BUG 382063
+    QScopedPointer<Surface> surface1(Test::createSurface());
+    QScopedPointer<QObject> shellSurface1(Test::createShellSurface(Test::ShellSurfaceType::WlShell, surface1.data()));
+    auto client = Test::renderAndWaitForShown(surface1.data(), QSize(100, 50), Qt::blue);
+    QVERIFY(client);
+
+    workspace()->showWindowMenu(QRect(), client);
+    auto userActionsMenu = workspace()->userActionsMenu();
+    QTRY_VERIFY(userActionsMenu->isShown());
+    QVERIFY(userActionsMenu->hasClient());
+
+    kwinApp()->platform()->keyboardKeyPressed(KEY_ESC, 0);
+    kwinApp()->platform()->keyboardKeyReleased(KEY_ESC, 1);
+    QTRY_VERIFY(!userActionsMenu->isShown());
+    QVERIFY(!userActionsMenu->hasClient());
+
+    // and show again, this triggers BUG 382063
+    workspace()->showWindowMenu(QRect(), client);
+    QTRY_VERIFY(userActionsMenu->isShown());
+    QVERIFY(userActionsMenu->hasClient());
+}
+
+WAYLANDTEST_MAIN(TestDontCrashUseractionsMenu)
+#include "dont_crash_useractions_menu.moc"

plugins/qpa/backingstore.cpp

@@ -74,6 +74,9 @@ void BackingStore::flush(QWindow *window, const QRegion &region, const QPoint &o
     Q_UNUSED(region)
     Q_UNUSED(offset)
     auto s = static_cast<Window *>(window->handle())->surface();
+    if (!s) {
+        return;
+    }
     s->attachBuffer(m_buffer);
     // TODO: proper damage region
     s->damage(QRect(QPoint(0, 0), m_backBuffer.size()));

plugins/qpa/nativeinterface.cpp

@@ -73,7 +73,9 @@ void *NativeInterface::nativeResourceForWindow(const QByteArray &resource, QWind
     }
     if (r == s_surfaceKey && window) {
         if (auto handle = window->handle()) {
-            return static_cast<wl_surface*>(*static_cast<Window*>(handle)->surface());
+            if (auto surface = static_cast<Window*>(handle)->surface()) {
+                return static_cast<wl_surface*>(*surface);
+            }
         }
     }
     return nullptr;