From c16a8e09d7e80b2130a0ba041b62b956b8c8ceb3 Mon Sep 17 00:00:00 2001
From: Xaver Hugl <xaver.hugl@gmail.com>
Date: Mon, 28 Mar 2022 18:08:59 +0200
Subject: [PATCH] waylandserver: only signal lockScreenShown once it has
 actually been shown

When the system goes to suspend and screen locking for suspend is enabled,
suspend is inhibited until ScreenLocker::KSldApp::self()->lockScreenShown()
gets called, in order to make sure that the lockscreen is shown before the
system goes to standby, and thus also when the system wakes (instead of
potentially sensitive user information).
However, signalling that when the lockscreen gets mapped can't work reliably,
as it's then a matter of timing whether or not KWin actually presents an
image with the lockscreen before suspending. To fix that, this commit replaces
that logic with only calling lockScreenShown once every output actually got a
lockscreen presented.
---
 src/wayland_server.cpp | 29 +++++++++++++++++++++++------
 src/wayland_server.h   | 10 ++++++++++
 2 files changed, 33 insertions(+), 6 deletions(-)

diff --git a/src/wayland_server.cpp b/src/wayland_server.cpp
index 2ab63149dd..677799afff 100644
--- a/src/wayland_server.cpp
+++ b/src/wayland_server.cpp
@@ -581,12 +581,6 @@ void WaylandServer::initScreenLocker()
 
     ScreenLocker::KSldApp::self()->setGreeterEnvironment(kwinApp()->processStartupEnvironment());
 
-    connect(this, &WaylandServer::shellClientAdded, this, [](AbstractClient *client) {
-        if (client->isLockScreen()) {
-            ScreenLocker::KSldApp::self()->lockScreenShown();
-        }
-    });
-
     connect(ScreenLocker::KSldApp::self(), &ScreenLocker::KSldApp::aboutToLock, this, [this, screenLockerApp]() {
         if (m_screenLockerClientConnection) {
             // Already sent data to KScreenLocker.
@@ -598,6 +592,8 @@ void WaylandServer::initScreenLocker()
         }
         ScreenLocker::KSldApp::self()->setWaylandFd(clientFd);
 
+        new LockScreenPresentationWatcher(this);
+
         const QVector<SeatInterface *> seatIfaces = m_display->seats();
         for (auto *seat : seatIfaces) {
             connect(seat, &KWaylandServer::SeatInterface::timestampChanged,
@@ -794,4 +790,25 @@ QString WaylandServer::socketName() const
     return QString();
 }
 
+#if KWIN_BUILD_SCREENLOCKER
+WaylandServer::LockScreenPresentationWatcher::LockScreenPresentationWatcher(WaylandServer *server)
+{
+    connect(server, &WaylandServer::shellClientAdded, this, [this](AbstractClient *client) {
+        if (client->isLockScreen()) {
+            connect(client->output()->renderLoop(), &RenderLoop::framePresented, this, [this, client]() {
+                // only signal lockScreenShown once all outputs have been presented at least once
+                m_signaledOutputs << client->output();
+                if (m_signaledOutputs.size() == kwinApp()->platform()->enabledOutputs().size()) {
+                    ScreenLocker::KSldApp::self()->lockScreenShown();
+                    delete this;
+                }
+            });
+        }
+    });
+    QTimer::singleShot(1000, this, [this]() {
+        ScreenLocker::KSldApp::self()->lockScreenShown();
+        delete this;
+    });
+}
+#endif
 }
diff --git a/src/wayland_server.h b/src/wayland_server.h
index e1d740549d..a20ba65e27 100644
--- a/src/wayland_server.h
+++ b/src/wayland_server.h
@@ -252,6 +252,16 @@ private:
     void handleOutputRemoved(AbstractOutput *output);
     void handleOutputEnabled(AbstractOutput *output);
     void handleOutputDisabled(AbstractOutput *output);
+
+    class LockScreenPresentationWatcher : public QObject
+    {
+    public:
+        LockScreenPresentationWatcher(WaylandServer *server);
+
+    private:
+        QSet<AbstractOutput *> m_signaledOutputs;
+    };
+
     KWaylandServer::Display *m_display = nullptr;
     KWaylandServer::CompositorInterface *m_compositor = nullptr;
     KWaylandServer::SeatInterface *m_seat = nullptr;