Add QmlImageProvider to allow asynchronous access to images.

Setting an image source to image://providerid/imageid will pass the
request for imageid to the provider registered for providerid.
QmlImageProvider::request() is run in a low priority thread, so the
main thread is not blocked while the image is loaded/rendered.

Reviewed-by: Aaron Kennedy

7 files changed, 250 insertions, 23 deletions

diff --git a/src/declarative/qml/qml.pri b/src/declarative/qml/qml.pri
index cd2fbff..021ef9e 100644
--- a/src/declarative/qml/qml.pri
+++ b/src/declarative/qml/qml.pri
@@ -50,6 +50,7 @@ SOURCES += \
     $$PWD/qmltypenamescriptclass.cpp \
     $$PWD/qmllistscriptclass.cpp \
     $$PWD/qmlworkerscript.cpp \
+    $$PWD/qmlimageprovider.cpp \
     $$PWD/qmlnetworkaccessmanagerfactory.cpp
 HEADERS += \
     $$PWD/qmlparser_p.h \
@@ -117,6 +118,7 @@ HEADERS += \
     $$PWD/qmlworkerscript_p.h \
     $$PWD/qmlscriptclass_p.h \
     $$PWD/qmlguard_p.h \
+    $$PWD/qmlimageprovider.h \
     $$PWD/qmlnetworkaccessmanagerfactory.h
 QT += sql
 include(parser/parser.pri)
diff --git a/src/declarative/qml/qmlengine.cpp b/src/declarative/qml/qmlengine.cpp
index cdbe5f3..4edab4d 100644
--- a/src/declarative/qml/qmlengine.cpp
+++ b/src/declarative/qml/qmlengine.cpp
@@ -65,6 +65,7 @@
 #include "qmlcomponent_p.h"
 #include "qmlscriptclass_p.h"
 #include "qmlnetworkaccessmanagerfactory.h"
+#include "qmlimageprovider.h"
 
 #include <qfxperf_p_p.h>
 
@@ -85,6 +86,7 @@
 #include <QtCore/qthread.h>
 #include <QtCore/qcoreapplication.h>
 #include <QtCore/qdir.h>
+#include <QtCore/qmutex.h>
 #include <QtGui/qcolor.h>
 #include <QtGui/qvector3d.h>
 #include <QtGui/qsound.h>
@@ -424,6 +426,7 @@ QmlContext *QmlEngine::rootContext()
 void QmlEngine::setNetworkAccessManagerFactory(QmlNetworkAccessManagerFactory *factory)
 {
     Q_D(QmlEngine);
+    QMutexLocker locker(&d->mutex);
     d->networkAccessManagerFactory = factory;
 }
 
@@ -438,17 +441,24 @@ QmlNetworkAccessManagerFactory *QmlEngine::networkAccessManagerFactory() const
     return d->networkAccessManagerFactory;
 }
 
+QNetworkAccessManager *QmlEnginePrivate::createNetworkAccessManager(QObject *parent) const
+{
+    QMutexLocker locker(&mutex);
+    QNetworkAccessManager *nam;
+    if (networkAccessManagerFactory) {
+        nam = networkAccessManagerFactory->create(parent);
+    } else {
+        nam = new QNetworkAccessManager(parent);
+    }
+
+    return nam;
+}
+
 QNetworkAccessManager *QmlEnginePrivate::getNetworkAccessManager() const
 {
     Q_Q(const QmlEngine);
-
-    if (!networkAccessManager) {
-        if (networkAccessManagerFactory) {
-            networkAccessManager = networkAccessManagerFactory->create(const_cast<QmlEngine*>(q));
-        } else {
-            networkAccessManager = new QNetworkAccessManager(const_cast<QmlEngine*>(q));
-        }
-    }
+    if (!networkAccessManager)
+        networkAccessManager = createNetworkAccessManager(const_cast<QmlEngine*>(q));
     return networkAccessManager;
 }
 
@@ -470,6 +480,69 @@ QNetworkAccessManager *QmlEngine::networkAccessManager() const
 }
 
 /*!
+    Sets the \a provider to use for images requested via the \e image: url
+    scheme, with host \a providerId.
+
+    QmlImageProvider allows images to be provided to QML asynchronously.
+    The image request will be run in a low priority thread.  This allows
+    potentially costly image loading to be done in the background, without
+    affecting the performance of the UI.
+
+    Note that images loaded from a QmlImageProvider are cached by
+    QPixmapCache, similar to any image loaded by QML.
+
+    The QmlEngine assumes ownership of the provider.
+
+    This example creates a provider with id \e colors:
+
+    \snippet examples/declarative/imageprovider/main.cpp 0
+
+    \snippet examples/declarative/imageprovider/view.qml 0
+
+    \sa removeImageProvider()
+*/
+void QmlEngine::addImageProvider(const QString &providerId, QmlImageProvider *provider)
+{
+    Q_D(QmlEngine);
+    QMutexLocker locker(&d->mutex);
+    d->imageProviders.insert(providerId, provider);
+}
+
+/*!
+    Returns the QmlImageProvider set for \a providerId.
+*/
+QmlImageProvider *QmlEngine::imageProvider(const QString &providerId) const
+{
+    Q_D(const QmlEngine);
+    QMutexLocker locker(&d->mutex);
+    return d->imageProviders.value(providerId);
+}
+
+/*!
+    Removes the QmlImageProvider for \a providerId.
+
+    Returns the provider if it was found; otherwise returns 0.
+
+    \sa addImageProvider()
+*/
+void QmlEngine::removeImageProvider(const QString &providerId)
+{
+    Q_D(QmlEngine);
+    QMutexLocker locker(&d->mutex);
+    delete d->imageProviders.take(providerId);
+}
+
+QImage QmlEnginePrivate::getImageFromProvider(const QUrl &url)
+{
+    QMutexLocker locker(&mutex);
+    QImage image;
+    QmlImageProvider *provider = imageProviders.value(url.host());
+    if (provider)
+        image = provider->request(url.path().mid(1));
+    return image;
+}
+
+/*!
     Return the base URL for this engine.  The base URL is only used to resolve
     components when a relative URL is passed to the QmlComponent constructor.
 
diff --git a/src/declarative/qml/qmlengine.h b/src/declarative/qml/qmlengine.h
index 7ee014a..a59a1ba 100644
--- a/src/declarative/qml/qmlengine.h
+++ b/src/declarative/qml/qmlengine.h
@@ -62,6 +62,7 @@ class QmlType;
 class QUrl;
 class QScriptEngine;
 class QScriptContext;
+class QmlImageProvider;
 class QNetworkAccessManager;
 class QmlNetworkAccessManagerFactory;
 class Q_DECLARATIVE_EXPORT QmlEngine : public QObject
@@ -83,6 +84,10 @@ public:
 
     QNetworkAccessManager *networkAccessManager() const;
 
+    void addImageProvider(const QString &id, QmlImageProvider *);
+    QmlImageProvider *imageProvider(const QString &id) const;
+    void removeImageProvider(const QString &id);
+
     void setOfflineStoragePath(const QString& dir);
     QString offlineStoragePath() const;
 
diff --git a/src/declarative/qml/qmlengine_p.h b/src/declarative/qml/qmlengine_p.h
index 13ed5ef..87864b7 100644
--- a/src/declarative/qml/qmlengine_p.h
+++ b/src/declarative/qml/qmlengine_p.h
@@ -75,6 +75,7 @@
 #include <QtCore/qlist.h>
 #include <QtCore/qpair.h>
 #include <QtCore/qstack.h>
+#include <QtCore/qmutex.h>
 #include <QtScript/qscriptengine.h>
 
 #include <private/qobject_p.h>
@@ -211,10 +212,16 @@ public:
 
     bool inBeginCreate;
 
+    QNetworkAccessManager *createNetworkAccessManager(QObject *parent) const;
     QNetworkAccessManager *getNetworkAccessManager() const;
     mutable QNetworkAccessManager *networkAccessManager;
     mutable QmlNetworkAccessManagerFactory *networkAccessManagerFactory;
 
+    QHash<QString,QmlImageProvider*> imageProviders;
+    QImage getImageFromProvider(const QUrl &url);
+
+    mutable QMutex mutex;
+
     QmlCompositeTypeManager typeManager;
     QStringList fileImportPath;
     QString offlineStoragePath;
diff --git a/src/declarative/qml/qmlimageprovider.cpp b/src/declarative/qml/qmlimageprovider.cpp
new file mode 100644
index 0000000..ebb8656
--- /dev/null
+++ b/src/declarative/qml/qmlimageprovider.cpp
@@ -0,0 +1,68 @@
+/****************************************************************************
+**
+** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the QtDeclarative module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the Technology Preview License Agreement accompanying
+** this package.
+**
+** 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 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain additional
+** rights.  These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qmlimageprovider.h"
+
+QT_BEGIN_NAMESPACE
+
+/*!
+    \class QmlImageProvider
+    \brief The QmlImageProvider class provides an interface for threaded image requests.
+
+    Note: the request() method may be called by multiple threads, so ensure the
+    implementation of this method is reentrant.
+
+    \sa QmlEngine::addImageProvider()
+*/
+QmlImageProvider::~QmlImageProvider()
+{
+}
+
+/*!
+    \fn QImage QmlImageProvider::request(const QString &id)
+
+    Implement this method to return the image with \a id.
+
+    Note: this method may be called by multiple threads, so ensure the
+    implementation of this method is reentrant.
+*/
+
+QT_END_NAMESPACE
diff --git a/src/declarative/qml/qmlimageprovider.h b/src/declarative/qml/qmlimageprovider.h
new file mode 100644
index 0000000..9804815
--- /dev/null
+++ b/src/declarative/qml/qmlimageprovider.h
@@ -0,0 +1,64 @@
+/****************************************************************************
+**
+** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the QtDeclarative module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the Technology Preview License Agreement accompanying
+** this package.
+**
+** 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 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain additional
+** rights.  These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QMLIMAGEPROVIDER_H
+#define QMLIMAGEPROVIDER_H
+
+#include <QtGui/qimage.h>
+
+QT_BEGIN_HEADER
+
+QT_BEGIN_NAMESPACE
+
+QT_MODULE(Declarative)
+
+class Q_DECLARATIVE_EXPORT QmlImageProvider
+{
+public:
+    virtual ~QmlImageProvider();
+    virtual QImage request(const QString &id) = 0;
+};
+
+QT_END_NAMESPACE
+
+QT_END_HEADER
+
+#endif // QMLIMAGEPROVIDER
diff --git a/src/declarative/util/qmlpixmapcache.cpp b/src/declarative/util/qmlpixmapcache.cpp
index c03b5df..623aaf0 100644
--- a/src/declarative/util/qmlpixmapcache.cpp
+++ b/src/declarative/util/qmlpixmapcache.cpp
@@ -41,11 +41,13 @@
 
 #include "qmlpixmapcache_p.h"
 #include "qmlnetworkaccessmanagerfactory.h"
+#include "qmlimageprovider.h"
 
 #include "qfxperf_p_p.h"
 
 #include <qmlengine.h>
 #include <private/qmlglobal_p.h>
+#include <private/qmlengine_p.h>
 
 #include <QCoreApplication>
 #include <QImageReader>
@@ -82,7 +84,7 @@ class QmlImageReaderEvent : public QEvent
 public:
     enum ReadError { NoError, Loading, Decoding };
 
-    QmlImageReaderEvent(QmlImageReaderEvent::ReadError err, const QString &errStr, QImage &img)
+    QmlImageReaderEvent(QmlImageReaderEvent::ReadError err, const QString &errStr, const QImage &img)
         : QEvent(QEvent::User), error(err), errorString(errStr), image(img) {}
 
     ReadError error;
@@ -143,13 +145,8 @@ private slots:
 
 private:
     QNetworkAccessManager *networkAccessManager() {
-        if (!accessManager) {
-            if (engine && engine->networkAccessManagerFactory()) {
-                accessManager = engine->networkAccessManagerFactory()->create(this);
-            } else {
-                accessManager = new QNetworkAccessManager(this);
-            }
-        }
+        if (!accessManager)
+            accessManager = QmlEnginePrivate::get(engine)->createNetworkAccessManager(this);
         return accessManager;
     }
 
@@ -197,21 +194,32 @@ bool QmlImageRequestHandler::event(QEvent *event)
                 break;
             }
 
-            QmlPixmapReply *runningJob = reader->jobs.takeFirst();
+            QmlPixmapReply *runningJob = reader->jobs.takeLast();
             runningJob->addRef();
             runningJob->setLoading();
             QUrl url = runningJob->url();
             reader->mutex.unlock();
 
             // fetch
-            QNetworkRequest req(url);
-            req.setAttribute(QNetworkRequest::HttpPipeliningAllowedAttribute, true);
-            QNetworkReply *reply = networkAccessManager()->get(req);
+            if (url.scheme() == QLatin1String("image")) {
+                QImage image = QmlEnginePrivate::get(engine)->getImageFromProvider(url);
+                QmlImageReaderEvent::ReadError errorCode = QmlImageReaderEvent::NoError;
+                QString errorStr;
+                if (image.isNull()) {
+                    errorCode = QmlImageReaderEvent::Loading;
+                    errorStr = QLatin1String("Failed to get image from provider: ") + url.toString();
+                }
+                QCoreApplication::postEvent(runningJob, new QmlImageReaderEvent(errorCode, errorStr, image));
+            } else {
+                QNetworkRequest req(url);
+                req.setAttribute(QNetworkRequest::HttpPipeliningAllowedAttribute, true);
+                QNetworkReply *reply = networkAccessManager()->get(req);
 
-            QMetaObject::connect(reply, replyDownloadProgress, runningJob, downloadProgress);
-            QMetaObject::connect(reply, replyFinished, this, thisNetworkRequestDone);
+                QMetaObject::connect(reply, replyDownloadProgress, runningJob, downloadProgress);
+                QMetaObject::connect(reply, replyFinished, this, thisNetworkRequestDone);
 
-            replies.insert(reply, runningJob);
+                replies.insert(reply, runningJob);
+            }
         }
         return true;
     }