From 0323825f76a52505eaaf820c9bea97cbe575bad1 Mon Sep 17 00:00:00 2001
From: Vlad Zahorodnii <vlad.zahorodnii@kde.org>
Date: Mon, 27 Apr 2020 13:49:36 +0300
Subject: [PATCH] [x11] Update X11 time stamp on Wayland

Assume that Xwayland's current X11 time stamp corresponds to the system
monotonic time. Unfortunately, we cannot make roundtrips to Xwayland and
we cannot query the time stamp asynchronously because it may introduce
regressions in the standalone X11 window manager.

Differential Revision: https://phabricator.kde.org/D29250
---
 platform.cpp                                  | 26 +++++++++++++++++++
 platform.h                                    |  8 ++----
 .../platforms/x11/standalone/x11_platform.cpp | 16 ------------
 .../platforms/x11/standalone/x11_platform.h   |  2 --
 4 files changed, 28 insertions(+), 24 deletions(-)

diff --git a/platform.cpp b/platform.cpp
index 257d9ea068..e986fd943b 100644
--- a/platform.cpp
+++ b/platform.cpp
@@ -37,6 +37,8 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include <KWayland/Server/outputconfiguration_interface.h>
 #include <KWayland/Server/outputchangeset.h>
 
+#include <QX11Info>
+
 namespace KWin
 {
 
@@ -501,8 +503,32 @@ OverlayWindow *Platform::createOverlayWindow()
     return nullptr;
 }
 
+static quint32 monotonicTime()
+{
+    timespec ts;
+
+    const int result = clock_gettime(CLOCK_MONOTONIC, &ts);
+    if (result)
+        qCWarning(KWIN_CORE, "Failed to query monotonic time: %s", strerror(errno));
+
+    return ts.tv_sec * 1000 + ts.tv_nsec / 1000000L;
+}
+
 void Platform::updateXTime()
 {
+    switch (kwinApp()->operationMode()) {
+    case Application::OperationModeX11:
+        kwinApp()->setX11Time(QX11Info::getTimestamp(), Application::TimestampUpdate::Always);
+        break;
+
+    case Application::OperationModeXwayland:
+        kwinApp()->setX11Time(monotonicTime(), Application::TimestampUpdate::Always);
+        break;
+
+    default:
+        // Do not update the current X11 time stamp if it's the Wayland only session.
+        break;
+    }
 }
 
 OutlineVisual *Platform::createOutline(Outline *outline)
diff --git a/platform.h b/platform.h
index d6da5c4e86..35d708fcb4 100644
--- a/platform.h
+++ b/platform.h
@@ -364,13 +364,9 @@ public:
     virtual OverlayWindow *createOverlayWindow();
 
     /**
-     * Allows a platform to update the X11 timestamp.
-     * Mostly for the X11 standalone platform to interact with QX11Info.
-     *
-     * Default implementation does nothing. This means code relying on the X timestamp being up to date,
-     * might not be working. E.g. synced X11 window resizing
+     * Queries the current X11 time stamp of the X server.
      */
-    virtual void updateXTime();
+    void updateXTime();
 
     /**
      * Creates the OutlineVisual for the given @p outline.
diff --git a/plugins/platforms/x11/standalone/x11_platform.cpp b/plugins/platforms/x11/standalone/x11_platform.cpp
index 92a8337912..7310d8df21 100644
--- a/plugins/platforms/x11/standalone/x11_platform.cpp
+++ b/plugins/platforms/x11/standalone/x11_platform.cpp
@@ -348,22 +348,6 @@ OverlayWindow *X11StandalonePlatform::createOverlayWindow()
     return new OverlayWindowX11();
 }
 
-/*
- Updates xTime(). This used to simply fetch current timestamp from the server,
- but that can cause xTime() to be newer than timestamp of events that are
- still in our events queue, thus e.g. making XSetInputFocus() caused by such
- event to be ignored. Therefore events queue is searched for first
- event with timestamp, and extra PropertyNotify is generated in order to make
- sure such event is found.
-*/
-void X11StandalonePlatform::updateXTime()
-{
-    // NOTE: QX11Info::getTimestamp does not yet search the event queue as the old
-    // solution did. This means there might be regressions currently. See the
-    // documentation above on how it should be done properly.
-    kwinApp()->setX11Time(QX11Info::getTimestamp(), Application::TimestampUpdate::Always);
-}
-
 OutlineVisual *X11StandalonePlatform::createOutline(Outline *outline)
 {
     // first try composited Outline
diff --git a/plugins/platforms/x11/standalone/x11_platform.h b/plugins/platforms/x11/standalone/x11_platform.h
index ac6fff0ac9..78a12704bf 100644
--- a/plugins/platforms/x11/standalone/x11_platform.h
+++ b/plugins/platforms/x11/standalone/x11_platform.h
@@ -62,8 +62,6 @@ public:
     void setupActionForGlobalAccel(QAction *action) override;
 
     OverlayWindow *createOverlayWindow() override;
-
-    void updateXTime() override;
     OutlineVisual *createOutline(Outline *outline) override;
     Decoration::Renderer *createDecorationRenderer(Decoration::DecoratedClientImpl *client) override;