QWindowsTheme: Run SHGetFileInfo() in a thread.

Windows 10: SHGetFileInfo() (as called by item views on file system
models has been observed to trigger a WM_PAINT on the mainwindow
for totally obscure reasons, causing a recursive repaint. Suppress
this by running it via QThreadPool.

Task-number: QTBUG-45298
Task-number: QTBUG-48823
Task-number: QTCREATORBUG-14888
Change-Id: I7479102b9b8fb0771681260298c3d735e66f220f
Reviewed-by: Joerg Bornemann <joerg.bornemann@theqtcompany.com>

src/plugins/platforms/windows/qwindowstheme.cpp

@@ -122,6 +122,41 @@ static inline QColor getSysColor(int index)
     return COLORREFToQColor(GetSysColor(index));
 }
 
+#ifndef QT_NO_WINCE_SHELLSDK
+// QTBUG-48823/Windows 10: SHGetFileInfo() (as called by item views on file system
+// models has been observed to trigger a WM_PAINT on the mainwindow. Suppress the
+// behavior by running it in a thread.
+class ShGetFileInfoFunction
+{
+public:
+    explicit ShGetFileInfoFunction(const wchar_t *fn, DWORD a, SHFILEINFO *i, UINT f, bool *r) :
+        m_fileName(fn), m_attributes(a), m_flags(f), m_info(i), m_result(r) {}
+
+    void operator()() const { *m_result = SHGetFileInfo(m_fileName, m_attributes, m_info, sizeof(SHFILEINFO), m_flags); }
+
+private:
+    const wchar_t *m_fileName;
+    const DWORD m_attributes;
+    const UINT m_flags;
+    SHFILEINFO *const m_info;
+    bool *m_result;
+};
+
+static bool shGetFileInfoBackground(QWindowsThreadPoolRunner &r,
+                                    const wchar_t *fileName, DWORD attributes,
+                                    SHFILEINFO *info, UINT flags,
+                                    unsigned long  timeOutMSecs = 5000)
+{
+    bool result = false;
+    if (!r.run(ShGetFileInfoFunction(fileName, attributes, info, flags, &result), timeOutMSecs)) {
+        qWarning().noquote() << "ShGetFileInfoBackground() timed out for "
+            << QString::fromWCharArray(fileName);
+        return false;
+    }
+    return result;
+}
+#endif // !QT_NO_WINCE_SHELLSDK
+
 // from QStyle::standardPalette
 static inline QPalette standardPalette()
 {
@@ -690,23 +725,22 @@ QPixmap QWindowsTheme::fileIconPixmap(const QFileInfo &fileInfo, const QSizeF &s
     }
 
     SHFILEINFO info;
-    unsigned int flags =
+    const unsigned int flags =
 #ifndef Q_OS_WINCE
         SHGFI_ICON|iconSize|SHGFI_SYSICONINDEX|SHGFI_ADDOVERLAYS|SHGFI_OVERLAYINDEX;
 #else
         iconSize|SHGFI_SYSICONINDEX;
 #endif // Q_OS_WINCE
-    unsigned long val = 0;
+
+
 #if !defined(QT_NO_WINCE_SHELLSDK)
-    if (cacheableDirIcon && useDefaultFolderIcon) {
+    const bool val = cacheableDirIcon && useDefaultFolderIcon
-        flags |= SHGFI_USEFILEATTRIBUTES;
+        ? shGetFileInfoBackground(m_threadPoolRunner, L"dummy", FILE_ATTRIBUTE_DIRECTORY,
-        val = SHGetFileInfo(L"dummy",
+                                  &info, flags | SHGFI_USEFILEATTRIBUTES)
-                            FILE_ATTRIBUTE_DIRECTORY,
+        : shGetFileInfoBackground(m_threadPoolRunner, reinterpret_cast<const wchar_t *>(filePath.utf16()), 0,
-                            &info, sizeof(SHFILEINFO), flags);
+                                  &info, flags);
-    } else {
+#else
-        val = SHGetFileInfo(reinterpret_cast<const wchar_t *>(filePath.utf16()), 0,
+    const bool val = false;
-                            &info, sizeof(SHFILEINFO), flags);
-    }
 #endif // !QT_NO_WINCE_SHELLSDK
 
     // Even if GetFileInfo returns a valid result, hIcon can be empty in some cases

src/plugins/platforms/windows/qwindowstheme.h

@@ -34,6 +34,7 @@
 #ifndef QWINDOWSTHEME_H
 #define QWINDOWSTHEME_H
 
+#include "qwindowsthreadpoolrunner.h"
 #include <qpa/qplatformtheme.h>
 
 QT_BEGIN_NAMESPACE
@@ -74,6 +75,7 @@ private:
     static QWindowsTheme *m_instance;
     QPalette *m_palettes[NPalettes];
     QFont *m_fonts[NFonts];
+    mutable QWindowsThreadPoolRunner m_threadPoolRunner;
 };
 
 QT_END_NAMESPACE

src/plugins/platforms/windows/qwindowsthreadpoolrunner.h

@@ -0,0 +1,116 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the plugins of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL21$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 or version 3 as published by the Free
+** Software Foundation and appearing in the file LICENSE.LGPLv21 and
+** LICENSE.LGPLv3 included in the packaging of this file. Please review the
+** following information to ensure the GNU Lesser General Public License
+** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** As a special exception, The Qt Company gives you certain additional
+** rights. These rights are described in The Qt Company LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QWINDOWSTHREADPOOLRUNNER_H
+#define QWINDOWSTHREADPOOLRUNNER_H
+
+#include <QtCore/QMutex>
+#include <QtCore/QRunnable>
+#include <QtCore/QThreadPool>
+#include <QtCore/QWaitCondition>
+
+QT_BEGIN_NAMESPACE
+
+/*!
+    \class QWindowsThreadPoolRunner
+    \brief Runs a task in the global instance of QThreadPool
+
+    QThreadPool does not provide a method to wait on a single task, so this needs
+    to be done by using QWaitCondition/QMutex.
+
+    \internal
+    \ingroup qt-lighthouse-win
+*/
+class QWindowsThreadPoolRunner
+{
+    Q_DISABLE_COPY(QWindowsThreadPoolRunner)
+
+#ifndef QT_NO_THREAD
+    template <class RunnableFunction> // nested class implementing QRunnable to execute a function.
+    class Runnable : public QRunnable
+    {
+    public:
+        explicit Runnable(QMutex *m, QWaitCondition *c, RunnableFunction f)
+            : m_mutex(m), m_condition(c), m_function(f) {}
+
+        void run() Q_DECL_OVERRIDE
+        {
+            m_function();
+            m_mutex->lock();
+            m_condition->wakeAll();
+            m_mutex->unlock();
+        }
+
+    private:
+        QMutex *m_mutex;
+        QWaitCondition *m_condition;
+        RunnableFunction m_function;
+    }; // class Runnable
+
+public:
+    QWindowsThreadPoolRunner() {}
+
+    template <class Function>
+    bool run(Function f, unsigned long timeOutMSecs = 5000)
+    {
+        QThreadPool *pool = QThreadPool::globalInstance();
+        Q_ASSERT(pool);
+        Runnable<Function> *runnable = new Runnable<Function>(&m_mutex, &m_condition, f);
+        m_mutex.lock();
+        pool->start(runnable);
+        const bool ok = m_condition.wait(&m_mutex, timeOutMSecs);
+        m_mutex.unlock();
+        if (!ok)
+            pool->cancel(runnable);
+        return ok;
+    }
+
+private:
+    QMutex m_mutex;
+    QWaitCondition m_condition;
+#else // !QT_NO_THREAD
+public:
+    QWindowsThreadPoolRunner() {}
+
+    template <class Function>
+    bool run(Function f, unsigned long /* timeOutMSecs */ = 5000)
+    {
+        f();
+        return true;
+    }
+#endif // QT_NO_THREAD
+};
+
+QT_END_NAMESPACE
+
+#endif // QWINDOWSTHREADPOOLRUNNER_H

src/plugins/platforms/windows/windows.pri

@@ -63,7 +63,8 @@ HEADERS += \
     $$PWD/qplatformfunctions_wince.h \
     $$PWD/qwindowsnativeimage.h \
     $$PWD/qwindowsnativeinterface.h \
-    $$PWD/qwindowsopengltester.h
+    $$PWD/qwindowsopengltester.h \
+    $$PWD/qwindowsthreadpoolrunner.h
 
 INCLUDEPATH += $$PWD