From 61e6e8dfc9b39c85a4e2865012c1e47723717376 Mon Sep 17 00:00:00 2001
From: Heather Anderson <heath@odysseus.anderson.name>
Date: Wed, 22 Apr 2020 23:16:51 -0700
Subject: [PATCH] Restructure ContextAwareProfile from a (thread-blocking)
 polling to a threadsafe-notification

---
 .../ui/src/ui/types/ContextAwareProfile.cpp   | 65 +++++++++++++++----
 .../ui/src/ui/types/ContextAwareProfile.h     | 40 ++++++++++--
 2 files changed, 89 insertions(+), 16 deletions(-)

diff --git a/libraries/ui/src/ui/types/ContextAwareProfile.cpp b/libraries/ui/src/ui/types/ContextAwareProfile.cpp
index f74e8754c9..d5b8d958b6 100644
--- a/libraries/ui/src/ui/types/ContextAwareProfile.cpp
+++ b/libraries/ui/src/ui/types/ContextAwareProfile.cpp
@@ -20,20 +20,62 @@
 
 static const QString RESTRICTED_FLAG_PROPERTY = "RestrictFileAccess";
 
-ContextAwareProfile::ContextAwareProfile(QQmlContext* context) :
-    ContextAwareProfileParent(context), _context(context) { 
-    assert(context);
+QMutex RestrictedContextMonitor::gl_monitorMapProtect;
+RestrictedContextMonitor::TMonitorMap RestrictedContextMonitor::gl_monitorMap;
+
+RestrictedContextMonitor::~RestrictedContextMonitor() {
+    gl_monitorMapProtect.lock();
+    TMonitorMap::iterator lookup = gl_monitorMap.find(context);
+    if (lookup != gl_monitorMap.end()) {
+        gl_monitorMap.erase(lookup);
+    }
+    gl_monitorMapProtect.unlock();
 }
 
+RestrictedContextMonitor::TSharedPtr RestrictedContextMonitor::getMonitor(QQmlContext* context, bool createIfMissing) {
+    TSharedPtr monitor;
+
+    gl_monitorMapProtect.lock();
+    TMonitorMap::const_iterator lookup = gl_monitorMap.find(context);
+    if (lookup != gl_monitorMap.end()) {
+        monitor = lookup->second.lock();
+        assert(monitor);
+    } else if(createIfMissing) {
+        monitor = std::make_shared<RestrictedContextMonitor>(context);
+        monitor->selfPtr = monitor;
+        gl_monitorMap.insert(TMonitorMap::value_type(context, monitor));
+    }
+    gl_monitorMapProtect.unlock();
+    return monitor;
+}
+
+ContextAwareProfile::ContextAwareProfile(QQmlContext* context) : ContextAwareProfileParent(context), _context(context) {
+    assert(context);
+
+    _monitor = RestrictedContextMonitor::getMonitor(context, true);
+    assert(_monitor);
+    connect(_monitor.get(), &RestrictedContextMonitor::onIsRestrictedChanged, this, &ContextAwareProfile::onIsRestrictedChanged);
+    if (_monitor->isUninitialized) {
+        _monitor->isRestricted = isRestrictedGetProperty();
+        _monitor->isUninitialized = false;
+    }
+    _isRestricted.store(_monitor->isRestricted ? 1 : 0);
+}
 
 void ContextAwareProfile::restrictContext(QQmlContext* context, bool restrict) {
+    RestrictedContextMonitor::TSharedPtr monitor = RestrictedContextMonitor::getMonitor(context, false);
+
     context->setContextProperty(RESTRICTED_FLAG_PROPERTY, restrict);
+    if (monitor && monitor->isRestricted != restrict) {
+        monitor->isRestricted = restrict;
+        monitor->onIsRestrictedChanged(restrict);
+    }
 }
 
-bool ContextAwareProfile::isRestrictedInternal() {
+bool ContextAwareProfile::isRestrictedGetProperty() {
     if (QThread::currentThread() != thread()) {
         bool restrictedResult = false;
-        BLOCKING_INVOKE_METHOD(this, "isRestrictedInternal", Q_RETURN_ARG(bool, restrictedResult));
+        BLOCKING_INVOKE_METHOD(this, "isRestrictedGetProperty", Q_RETURN_ARG(bool, restrictedResult));
         return restrictedResult;
     }
 
@@ -47,11 +89,10 @@ bool ContextAwareProfile::isRestrictedInternal() {
     return true;
 }
 
-bool ContextAwareProfile::isRestricted() {
-    auto now = usecTimestampNow();
-    if (now > _cacheExpiry) {
-        _cachedValue = isRestrictedInternal();
-        _cacheExpiry = now + MAX_CACHE_AGE;
-    }
-    return _cachedValue;
+void ContextAwareProfile::onIsRestrictedChanged(bool newValue) {
+    _isRestricted.store(newValue ? 1 : 0);
+}
+
+bool ContextAwareProfile::isRestricted() {
+    return _isRestricted.load() != 0;
 }
diff --git a/libraries/ui/src/ui/types/ContextAwareProfile.h b/libraries/ui/src/ui/types/ContextAwareProfile.h
index 3192d2be54..30bdad4b78 100644
--- a/libraries/ui/src/ui/types/ContextAwareProfile.h
+++ b/libraries/ui/src/ui/types/ContextAwareProfile.h
@@ -12,6 +12,7 @@
 #define hifi_ContextAwareProfile_h
 
 #include <QtCore/QtGlobal>
+#include <QtCore/QMutex>
 
 #if !defined(Q_OS_ANDROID)
 #include <QtWebEngine/QQuickWebEngineProfile>
@@ -30,12 +31,39 @@ using RequestInterceptorParent = QObject;
 
 class QQmlContext;
 
+class RestrictedContextMonitor : public QObject {
+    Q_OBJECT
+public:
+    typedef std::shared_ptr<RestrictedContextMonitor> TSharedPtr;
+    typedef std::weak_ptr<RestrictedContextMonitor> TWeakPtr;
+
+    inline RestrictedContextMonitor(QQmlContext* c) : context(c) {}
+    ~RestrictedContextMonitor();
+
+    static TSharedPtr getMonitor(QQmlContext* context, bool createIfMissing);
+
+signals:
+    void onIsRestrictedChanged(bool newValue);
+
+public:
+    TWeakPtr selfPtr;
+    QQmlContext* context{ nullptr };
+    bool isRestricted{ true };
+    bool isUninitialized{ true };
+
+private:
+    typedef std::map<QQmlContext*, TWeakPtr> TMonitorMap;
+
+    static QMutex gl_monitorMapProtect;
+    static TMonitorMap gl_monitorMap;
+};
+
 class ContextAwareProfile : public ContextAwareProfileParent {
     Q_OBJECT
 public:
     static void restrictContext(QQmlContext* context, bool restrict = true);
     bool isRestricted();
-    Q_INVOKABLE bool isRestrictedInternal();
+    Q_INVOKABLE bool isRestrictedGetProperty();
 protected:
 
     class RequestInterceptor : public RequestInterceptorParent {
@@ -48,9 +76,13 @@ protected:
 
     ContextAwareProfile(QQmlContext* parent);
     QQmlContext* _context{ nullptr };
-    bool _cachedValue{ false };
-    quint64 _cacheExpiry{ 0 };
-    constexpr static quint64 MAX_CACHE_AGE = MSECS_PER_SECOND;
+    QAtomicInt _isRestricted{ 0 };
+
+private slots:
+    void onIsRestrictedChanged(bool newValue);
+
+private:
+    RestrictedContextMonitor::TSharedPtr _monitor;
 };
 
 #endif // hifi_FileTypeProfile_h