From 6210b6bb8af128c8e93c77330af80185d8ac3bec Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20Gr=C3=A4=C3=9Flin?= <mgraesslin@kde.org>
Date: Wed, 21 May 2014 08:10:07 +0200
Subject: [PATCH 1/1] Ensure the xcb connection gets flushed before the event
 dispatcher blocks

This is a workaround for Qt versions which do not yet have the change
https://codereview.qt-project.org/85654

It is important to have this workaround as applications can get stalled
when a framework uses xcb and doesn't flush the connection manually.

BUG: 334858
REVIEW: 118234
---
 src/platformtheme/CMakeLists.txt               | 19 +++++++++++++++
 src/platformtheme/config-platformtheme.h.cmake |  1 +
 src/platformtheme/main.cpp                     | 33 ++++++++++++++++++++++++++
 3 files changed, 53 insertions(+)
 create mode 100644 src/platformtheme/config-platformtheme.h.cmake

diff --git a/src/platformtheme/CMakeLists.txt b/src/platformtheme/CMakeLists.txt
index da77cf8..8a3b1b4 100644
--- a/src/platformtheme/CMakeLists.txt
+++ b/src/platformtheme/CMakeLists.txt
@@ -1,3 +1,18 @@
+if(NOT APPLE)
+  find_package(XCB COMPONENTS XCB)
+  set_package_properties(XCB PROPERTIES
+    TYPE RECOMMENDED
+    PURPOSE "Required for flushing the XCB connection on the X11 Platform"
+  )
+  set(HAVE_X11 ${XCB_XCB_FOUND})
+  if (XCB_XCB_FOUND)
+    find_package(Qt5 ${REQUIRED_QT_VERSION} CONFIG REQUIRED X11Extras)
+  endif()
+else()
+    set(HAVE_X11 FALSE)
+endif()
+
+configure_file(config-platformtheme.h.cmake ${CMAKE_CURRENT_BINARY_DIR}/config-platformtheme.h )
 
 set(platformtheme_SRCS
     kdeplatformtheme.cpp
@@ -30,4 +45,8 @@ target_link_libraries(KDEPlatformTheme
         KF5::Notifications
 )
 
+if(HAVE_X11)
+  target_link_libraries(KDEPlatformTheme PRIVATE Qt5::X11Extras XCB::XCB)
+endif()
+
 install(TARGETS KDEPlatformTheme DESTINATION ${QT_PLUGIN_INSTALL_DIR}/platformthemes)
diff --git a/src/platformtheme/config-platformtheme.h.cmake b/src/platformtheme/config-platformtheme.h.cmake
new file mode 100644
index 0000000..89858d1
--- /dev/null
+++ b/src/platformtheme/config-platformtheme.h.cmake
@@ -0,0 +1 @@
+#cmakedefine01 HAVE_X11
diff --git a/src/platformtheme/main.cpp b/src/platformtheme/main.cpp
index 21d9aa0..d2c2bb1 100644
--- a/src/platformtheme/main.cpp
+++ b/src/platformtheme/main.cpp
@@ -22,6 +22,14 @@
 
 #include "kdeplatformtheme.h"
 
+#include <config-platformtheme.h>
+#if HAVE_X11
+#include <QCoreApplication>
+#include <QAbstractEventDispatcher>
+#include <QX11Info>
+#include <xcb/xcb.h>
+#endif
+
 class KdePlatformThemePlugin : public QPlatformThemePlugin
 {
     Q_OBJECT
@@ -34,8 +42,33 @@ public:
     {
         Q_UNUSED(key)
         Q_UNUSED(paramList)
+        // Must be done after we have an event-dispatcher. By posting a method invocation
+        // we are sure that by the time the method is called we have an event-dispatcher.
+        QMetaObject::invokeMethod(this, "setupXcbFlush", Qt::QueuedConnection);
         return new KdePlatformTheme;
     }
+
+public Q_SLOTS:
+    void setupXcbFlush();
 };
 
+void KdePlatformThemePlugin::setupXcbFlush()
+{
+#if HAVE_X11
+    // this is a workaround for BUG 334858
+    // it ensures that the xcb connection gets flushed before the EventDispatcher
+    // is going to block. Qt does not guarantee this in all cases.
+    // For Qt this issue is addressed in https://codereview.qt-project.org/85654
+    // TODO: remove again once we depend on a Qt version with the patch.
+    if (!QX11Info::isPlatformX11()) {
+        return;
+    }
+    connect(QCoreApplication::eventDispatcher(), &QAbstractEventDispatcher::aboutToBlock,
+        []() {
+            xcb_flush(QX11Info::connection());
+        }
+    );
+#endif
+}
+
 #include "main.moc"
-- 
1.9.3