wasm: add platform qsettings

Since the backend is async, the settings will not be ready to read/write
instantly as on other platforms, but only be ready after the
filesystem has been synced to the sandbox. This takes at least 250 to
500 ms. The QSettings status() or isWritable() can be used to discern when the
settings are ready for use.

This also fixes a crash in threaded wasm

Task-number: QTBUG-70002
Change-Id: I080bdb940aa8e9a126d7358b524f32477db151b6
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

6 files changed, 277 insertions, 38 deletions

diff --git a/src/corelib/io/io.pri b/src/corelib/io/io.pri
index fe81689932..c4c6f41387 100644
--- a/src/corelib/io/io.pri
+++ b/src/corelib/io/io.pri
@@ -136,6 +136,7 @@ qtConfig(settings) {
     } else: darwin:!nacl {
         SOURCES += io/qsettings_mac.cpp
     }
+    wasm : SOURCES += io/qsettings_wasm.cpp
 }
 
 win32 {
diff --git a/src/corelib/io/qsettings.cpp b/src/corelib/io/qsettings.cpp
index fc7122d904..dcc9340473 100644
--- a/src/corelib/io/qsettings.cpp
+++ b/src/corelib/io/qsettings.cpp
@@ -76,10 +76,6 @@
 #  include <ioLib.h>
 #endif
 
-#ifdef Q_OS_WASM
-#include <emscripten.h>
-#endif
-
 #include <algorithm>
 #include <stdlib.h>
 
@@ -295,7 +291,7 @@ after_loop:
 
 // see also qsettings_win.cpp, qsettings_winrt.cpp and qsettings_mac.cpp
 
-#if !defined(Q_OS_WIN) && !defined(Q_OS_MAC)
+#if !defined(Q_OS_WIN) && !defined(Q_OS_MAC) && !defined(Q_OS_WASM)
 QSettingsPrivate *QSettingsPrivate::create(QSettings::Format format, QSettings::Scope scope,
                                            const QString &organization, const QString &application)
 {
@@ -1185,7 +1181,9 @@ QConfFileSettingsPrivate::QConfFileSettingsPrivate(QSettings::Format format,
         confFiles.append(QConfFile::fromName(systemPath.path + orgFile, false));
     }
 
+#ifndef Q_OS_WASM // wasm needs to delay access until after file sync
     initAccess();
+#endif
 }
 
 QConfFileSettingsPrivate::QConfFileSettingsPrivate(const QString &fileName,
@@ -1548,13 +1546,6 @@ void QConfFileSettingsPrivate::syncConfFile(QConfFile *confFile)
                     perms |= QFile::ReadGroup | QFile::ReadOther;
                 QFile(confFile->name).setPermissions(perms);
             }
-#ifdef Q_OS_WASM
-        EM_ASM(
-            // Sync sandbox filesystem to persistent database filesystem. See QTBUG-70002
-            FS.syncfs(false, function(err) {
-            });
-        );
-#endif
         } else {
             setStatus(QSettings::AccessError);
         }
diff --git a/src/corelib/io/qsettings_p.h b/src/corelib/io/qsettings_p.h
index d18c96a06c..c30f099a72 100644
--- a/src/corelib/io/qsettings_p.h
+++ b/src/corelib/io/qsettings_p.h
@@ -57,6 +57,10 @@
 #include "QtCore/qiodevice.h"
 #include "QtCore/qstack.h"
 #include "QtCore/qstringlist.h"
+
+#include <QtCore/qvariant.h>
+#include "qsettings.h"
+
 #ifndef QT_NO_QOBJECT
 #include "private/qobject_p.h"
 #endif
@@ -253,6 +257,10 @@ protected:
     mutable QSettings::Status status;
 };
 
+#ifdef Q_OS_WASM
+class QWasmSettingsPrivate;
+#endif
+
 class QConfFileSettingsPrivate : public QSettingsPrivate
 {
 public:
@@ -281,7 +289,7 @@ public:
 
 private:
     void initFormat();
-    void initAccess();
+    virtual void initAccess();
     void syncConfFile(QConfFile *confFile);
     bool writeIniFile(QIODevice &device, const ParsedSettingsMap &map);
 #ifdef Q_OS_MAC
@@ -297,6 +305,9 @@ private:
     QString extension;
     Qt::CaseSensitivity caseSensitivity;
     int nextPosition;
+#ifdef Q_OS_WASM
+    friend class QWasmSettingsPrivate;
+#endif
 };
 
 QT_END_NAMESPACE
diff --git a/src/corelib/io/qsettings_wasm.cpp b/src/corelib/io/qsettings_wasm.cpp
new file mode 100644
index 0000000000..8d8f4b505c
--- /dev/null
+++ b/src/corelib/io/qsettings_wasm.cpp
@@ -0,0 +1,259 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtCore module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** 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 https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://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 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qsettings.h"
+#ifndef QT_NO_SETTINGS
+
+#include "qsettings_p.h"
+#ifndef QT_NO_QOBJECT
+#include "qcoreapplication.h"
+#include <QFile>
+#endif // QT_NO_QOBJECT
+#include <QDebug>
+
+#include <QFileInfo>
+#include <QDir>
+#include <emscripten.h>
+
+QT_BEGIN_NAMESPACE
+
+static bool isReadReady = false;
+
+class QWasmSettingsPrivate : public QConfFileSettingsPrivate
+{
+public:
+    QWasmSettingsPrivate(QSettings::Scope scope, const QString &organization,
+                        const QString &application);
+    ~QWasmSettingsPrivate();
+
+    bool get(const QString &key, QVariant *value) const override;
+    QStringList children(const QString &prefix, ChildSpec spec) const override;
+    void clear() override;
+    void sync() override;
+    void flush() override;
+    bool isWritable() const override;
+
+    void syncToLocal(const char *data, int size);
+    void loadLocal(const QByteArray &filename);
+    void setReady();
+    void initAccess() override;
+
+private:
+    QString databaseName;
+    QString id;
+};
+
+static void QWasmSettingsPrivate_onLoad(void *userData, void *dataPtr, int size)
+{
+    QWasmSettingsPrivate *wasm = reinterpret_cast<QWasmSettingsPrivate *>(userData);
+
+    QFile file(wasm->fileName());
+    QFileInfo fileInfo(wasm->fileName());
+    QDir dir(fileInfo.path());
+    if (!dir.exists())
+        dir.mkpath(fileInfo.path());
+
+    if (file.open(QFile::WriteOnly)) {
+        file.write(reinterpret_cast<char *>(dataPtr), size);
+        file.close();
+        wasm->setReady();
+    }
+}
+
+static void QWasmSettingsPrivate_onError(void *userData)
+{
+    QWasmSettingsPrivate *wasm = reinterpret_cast<QWasmSettingsPrivate *>(userData);
+    if (wasm)
+        wasm->setStatus(QSettings::AccessError);
+}
+
+static void QWasmSettingsPrivate_onStore(void *userData)
+{
+    QWasmSettingsPrivate *wasm = reinterpret_cast<QWasmSettingsPrivate *>(userData);
+    if (wasm)
+        wasm->setStatus(QSettings::NoError);
+}
+
+static void QWasmSettingsPrivate_onCheck(void *userData, int exists)
+{
+    QWasmSettingsPrivate *wasm = reinterpret_cast<QWasmSettingsPrivate *>(userData);
+    if (wasm) {
+        if (exists)
+            wasm->loadLocal(wasm->fileName().toLocal8Bit());
+        else
+            wasm->setReady();
+    }
+}
+
+QSettingsPrivate *QSettingsPrivate::create(QSettings::Format format,
+                                           QSettings::Scope scope,
+                                           const QString &organization,
+                                           const QString &application)
+{
+    Q_UNUSED(format)
+    if (organization == QLatin1String("Qt"))
+    {
+        QString organizationDomain = QCoreApplication::organizationDomain();
+        QString applicationName = QCoreApplication::applicationName();
+
+        QSettingsPrivate *newSettings;
+        newSettings = new QWasmSettingsPrivate(scope, organizationDomain, applicationName);
+
+        newSettings->beginGroupOrArray(QSettingsGroup(normalizedKey(organization)));
+        if (!application.isEmpty())
+            newSettings->beginGroupOrArray(QSettingsGroup(normalizedKey(application)));
+
+        return newSettings;
+    }
+    return new QWasmSettingsPrivate(scope, organization, application);
+}
+
+QWasmSettingsPrivate::QWasmSettingsPrivate(QSettings::Scope scope, const QString &organization,
+                                           const QString &application)
+    : QConfFileSettingsPrivate(QSettings::NativeFormat, scope, organization, application)
+{
+    setStatus(QSettings::AccessError); // access error until sandbox gets loaded
+    databaseName = organization;
+    id = application;
+
+    emscripten_idb_async_exists("/home/web_user",
+                                fileName().toLocal8Bit(),
+                                reinterpret_cast<void*>(this),
+                                QWasmSettingsPrivate_onCheck,
+                                QWasmSettingsPrivate_onError);
+}
+
+QWasmSettingsPrivate::~QWasmSettingsPrivate()
+{
+}
+
+ void QWasmSettingsPrivate::initAccess()
+{
+     if (isReadReady)
+         QConfFileSettingsPrivate::initAccess();
+}
+
+bool QWasmSettingsPrivate::get(const QString &key, QVariant *value) const
+{
+    if (isReadReady)
+        return QConfFileSettingsPrivate::get(key, value);
+
+    return false;
+}
+
+QStringList QWasmSettingsPrivate::children(const QString &prefix, ChildSpec spec) const
+{
+    return QConfFileSettingsPrivate::children(prefix, spec);
+}
+
+void QWasmSettingsPrivate::clear()
+{
+    QConfFileSettingsPrivate::clear();
+    emscripten_idb_async_delete("/home/web_user",
+                                fileName().toLocal8Bit(),
+                                reinterpret_cast<void*>(this),
+                                QWasmSettingsPrivate_onStore,
+                                QWasmSettingsPrivate_onError);
+}
+
+void QWasmSettingsPrivate::sync()
+{
+    QConfFileSettingsPrivate::sync();
+
+    QFile file(fileName());
+    if (file.open(QFile::ReadOnly)) {
+        QByteArray dataPointer = file.readAll();
+
+        emscripten_idb_async_store("/home/web_user",
+                                  fileName().toLocal8Bit(),
+                                   reinterpret_cast<void *>(dataPointer.data()),
+                                   dataPointer.length(),
+                                   reinterpret_cast<void*>(this),
+                                   QWasmSettingsPrivate_onStore,
+                                   QWasmSettingsPrivate_onError);
+    }
+}
+
+void QWasmSettingsPrivate::flush()
+{
+    sync();
+}
+
+bool QWasmSettingsPrivate::isWritable() const
+{
+    return isReadReady && QConfFileSettingsPrivate::isWritable();
+}
+
+void QWasmSettingsPrivate::syncToLocal(const char *data, int size)
+{
+    QFile file(fileName());
+
+    if (file.open(QFile::WriteOnly)) {
+        file.write(data, size + 1);
+        QByteArray data = file.readAll();
+
+        emscripten_idb_async_store("/home/web_user",
+                                   fileName().toLocal8Bit(),
+                                   reinterpret_cast<void *>(data.data()),
+                                   data.length(),
+                                   reinterpret_cast<void*>(this),
+                                   QWasmSettingsPrivate_onStore,
+                                   QWasmSettingsPrivate_onError);
+        setReady();
+    }
+}
+
+void QWasmSettingsPrivate::loadLocal(const QByteArray &filename)
+{
+    emscripten_idb_async_load("/home/web_user",
+                              filename.data(),
+                              reinterpret_cast<void*>(this),
+                              QWasmSettingsPrivate_onLoad,
+                              QWasmSettingsPrivate_onError);
+}
+
+void QWasmSettingsPrivate::setReady()
+{
+    isReadReady = true;
+    setStatus(QSettings::NoError);
+    QConfFileSettingsPrivate::initAccess();
+}
+
+QT_END_NAMESPACE
+#endif // QT_NO_SETTINGS
diff --git a/src/corelib/kernel/qcoreapplication.cpp b/src/corelib/kernel/qcoreapplication.cpp
index e25049f821..70f0a5ad4c 100644
--- a/src/corelib/kernel/qcoreapplication.cpp
+++ b/src/corelib/kernel/qcoreapplication.cpp
@@ -121,7 +121,6 @@
 #endif
 
 #ifdef Q_OS_WASM
-#include <emscripten.h>
 #include <emscripten/val.h>
 #endif
 
@@ -497,13 +496,6 @@ QCoreApplicationPrivate::QCoreApplicationPrivate(int &aargc, char **aargv, uint
 
 QCoreApplicationPrivate::~QCoreApplicationPrivate()
 {
-#ifdef Q_OS_WASM
-    EM_ASM(
-        // unmount persistent directory as IDBFS
-        // see also QTBUG-70002
-        FS.unmount('/home/web_user');
-    );
-#endif
 #ifndef QT_NO_QOBJECT
     cleanupThreadData();
 #endif
@@ -795,17 +787,8 @@ void QCoreApplicationPrivate::init()
     Q_ASSERT_X(!QCoreApplication::self, "QCoreApplication", "there should be only one application object");
     QCoreApplication::self = q;
 
-#ifdef Q_OS_WASM
-    EM_ASM(
-        // mount and sync persistent filesystem to sandbox
-        FS.mount(IDBFS, {}, '/home/web_user');
-        FS.syncfs(true, function(err) {
-            if (err)
-                Module.print(err);
-        });
-    );
-
 #if QT_CONFIG(thread)
+#ifdef Q_OS_WASM
     QThreadPrivate::idealThreadCount = emscripten::val::global("navigator")["hardwareConcurrency"].as<int>();
 #endif
 #endif
diff --git a/src/gui/kernel/qguiapplication.cpp b/src/gui/kernel/qguiapplication.cpp
index 4bb2507521..f1d90f9caa 100644
--- a/src/gui/kernel/qguiapplication.cpp
+++ b/src/gui/kernel/qguiapplication.cpp
@@ -1715,13 +1715,7 @@ QGuiApplicationPrivate::~QGuiApplicationPrivate()
         qt_gl_set_global_share_context(0);
     }
 #endif
-#ifdef Q_OS_WASM
-    EM_ASM(
-        // unmount persistent directory as IDBFS
-        // see QTBUG-70002
-        FS.unmount('/home/web_user');
-    );
-#endif
+
     platform_integration->destroy();
 
     delete platform_theme;