Extend QDeclarativeImageProvider to support QPixmap loading and

synchronous loading of QImages. (QPixmaps can only be created in the
main thread so they will always be loaded synchronously).

This changes request() to requestImage() and adds requestPixmap()
for pixmap support.

Task-number: QTBUG-11989
(cherry picked from commit a258456bcb35ec4211751a702ea94a1881d82a07)

5 files changed, 263 insertions, 46 deletions

diff --git a/src/declarative/qml/qdeclarativeengine.cpp b/src/declarative/qml/qdeclarativeengine.cpp
index 8b15ae9..c7fa3b3 100644
--- a/src/declarative/qml/qdeclarativeengine.cpp
+++ b/src/declarative/qml/qdeclarativeengine.cpp
@@ -620,24 +620,16 @@ QNetworkAccessManager *QDeclarativeEngine::networkAccessManager() const
 /*!
 
   Sets the \a provider to use for images requested via the \e
-  image: url scheme, with host \a providerId.
+  image: url scheme, with host \a providerId. The QDeclarativeEngine 
+  takes ownership of \a provider.
 
-  QDeclarativeImageProvider 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.
+  Image providers enable support for pixmap and threaded image
+  requests. See the QDeclarativeImageProvider documentation for details on
+  implementing and using image providers.
 
   Note that images loaded from a QDeclarativeImageProvider are cached
   by QPixmapCache, similar to any image loaded by QML.
 
-  The QDeclarativeEngine assumes ownership of the provider.
-
-  This example creates a provider with id \e colors:
-
-  \snippet examples/declarative/cppextensions/imageprovider/imageprovider.cpp 0
-
-  \snippet examples/declarative/cppextensions/imageprovider/imageprovider-example.qml 0
-
   \sa removeImageProvider()
 */
 void QDeclarativeEngine::addImageProvider(const QString &providerId, QDeclarativeImageProvider *provider)
@@ -671,16 +663,35 @@ void QDeclarativeEngine::removeImageProvider(const QString &providerId)
     delete d->imageProviders.take(providerId);
 }
 
+QDeclarativeImageProvider::ImageType QDeclarativeEnginePrivate::getImageProviderType(const QUrl &url)
+{
+    QMutexLocker locker(&mutex);
+    QDeclarativeImageProvider *provider = imageProviders.value(url.host());
+    if (provider)
+        return provider->imageType();
+    return static_cast<QDeclarativeImageProvider::ImageType>(-1);
+}
+
 QImage QDeclarativeEnginePrivate::getImageFromProvider(const QUrl &url, QSize *size, const QSize& req_size)
 {
     QMutexLocker locker(&mutex);
     QImage image;
     QDeclarativeImageProvider *provider = imageProviders.value(url.host());
     if (provider)
-        image = provider->request(url.path().mid(1), size, req_size);
+        image = provider->requestImage(url.path().mid(1), size, req_size);
     return image;
 }
 
+QPixmap QDeclarativeEnginePrivate::getPixmapFromProvider(const QUrl &url, QSize *size, const QSize& req_size)
+{
+    QMutexLocker locker(&mutex);
+    QPixmap pixmap;
+    QDeclarativeImageProvider *provider = imageProviders.value(url.host());
+    if (provider)
+        pixmap = provider->requestPixmap(url.path().mid(1), size, req_size);
+    return pixmap;
+}
+
 /*!
   Return the base URL for this engine.  The base URL is only used to
   resolve components when a relative URL is passed to the
diff --git a/src/declarative/qml/qdeclarativeengine_p.h b/src/declarative/qml/qdeclarativeengine_p.h
index cfa9d73..f457b53 100644
--- a/src/declarative/qml/qdeclarativeengine_p.h
+++ b/src/declarative/qml/qdeclarativeengine_p.h
@@ -64,6 +64,7 @@
 #include "qdeclarativecontext.h"
 #include "private/qdeclarativecontext_p.h"
 #include "qdeclarativeexpression.h"
+#include "qdeclarativeimageprovider.h"
 #include "private/qdeclarativeproperty_p.h"
 #include "private/qdeclarativepropertycache_p.h"
 #include "private/qdeclarativeobjectscriptclass_p.h"
@@ -233,7 +234,9 @@ public:
     mutable QDeclarativeNetworkAccessManagerFactory *networkAccessManagerFactory;
 
     QHash<QString,QDeclarativeImageProvider*> imageProviders;
+    QDeclarativeImageProvider::ImageType getImageProviderType(const QUrl &url);
     QImage getImageFromProvider(const QUrl &url, QSize *size, const QSize& req_size);
+    QPixmap getPixmapFromProvider(const QUrl &url, QSize *size, const QSize& req_size);
 
     mutable QMutex mutex;
 
diff --git a/src/declarative/qml/qdeclarativeimageprovider.cpp b/src/declarative/qml/qdeclarativeimageprovider.cpp
index f4a8588..f38da4e 100644
--- a/src/declarative/qml/qdeclarativeimageprovider.cpp
+++ b/src/declarative/qml/qdeclarativeimageprovider.cpp
@@ -43,35 +43,142 @@
 
 QT_BEGIN_NAMESPACE
 
+class QDeclarativeImageProviderPrivate
+{
+public:
+    QDeclarativeImageProvider::ImageType type;
+};
+
 /*!
     \class QDeclarativeImageProvider
     \since 4.7
-    \brief The QDeclarativeImageProvider class provides an interface for threaded image requests in QML.
+    \brief The QDeclarativeImageProvider class provides an interface for supporting pixmaps and threaded image requests in QML.
 
-    QDeclarativeImageProvider can be used by a QDeclarativeEngine to provide images to QML asynchronously.
-    The image request will be run in a low priority thread, allowing potentially costly image
-    loading to be done in the background, without affecting the performance of the UI.
+    QDeclarativeImageProvider is used to provide advanced image loading features
+    in QML applications. It allows images in QML to be:
 
-    See the QDeclarativeEngine::addImageProvider() documentation for an
-    example of how a custom QDeclarativeImageProvider can be constructed and used.
+    \list
+    \o Loaded using QPixmaps rather than actual image files
+    \o Loaded asynchronously in a separate thread, if imageType() is \l ImageType::Image
+    \endlist
 
-    \note the request() method may be called by multiple threads, so ensure the
-    implementation of this method is reentrant.
+    To specify that an image should be loaded by an image provider, use the
+    \bold {"image:"} scheme for the URL source of the image, followed by the 
+    identifiers of the image provider and the requested image. For example:
+   
+    \qml
+    Image { source: "image://myimageprovider/image.png" }
+    \endqml
+
+    This specifies that the image should be loaded by the image provider named 
+    "myimageprovider", and the image to be loaded is named "image.png". The QML engine 
+    invokes the appropriate image provider according to the providers that have
+    been registered through QDeclarativeEngine::addImageProvider().
+
+
+    \section2 An example
+
+    Here are two images. Their \c source values indicate they should be loaded by
+    an image provider named "colors", and the images to be loaded are "yellow"
+    and "red", respectively:
+
+    \snippet examples/declarative/cppextensions/imageprovider/imageprovider-example.qml 0
+ 
+    When these images are loaded by QML, it looks for a matching image provider
+    and calls its requestImage() or requestPixmap() method (depending on its
+    imageType()) to load the image. The method is called with the \c id 
+    parameter set to "yellow" for the first image, and "red" for the second.
+
+    Here is an image provider implementation that can load the images 
+    requested by the above QML. This implementation dynamically 
+    generates QPixmap images that are filled with the requested color:
+
+    \snippet examples/declarative/cppextensions/imageprovider/imageprovider.cpp 0
+    \codeline
+    \snippet examples/declarative/cppextensions/imageprovider/imageprovider.cpp 1
+
+    To make this provider accessible to QML, it is registered with the QML engine
+    with a "colors" identifier:
+
+    \code
+    int main(int argc, char *argv[]) 
+    {
+        ...
+
+        QDeclarativeEngine engine;
+        engine->addImageProvider(QLatin1String("colors"), new ColorPixmapProvider);
+
+        ...
+    }
+    \endcode
+
+    Now the images can be succesfully loaded in QML:
+
+    \image imageprovider.png
+
+    A complete example is available in Qt's 
+    \l {declarative/cppextensions/imageprovider}{examples/declarative/cppextensions/imageprovider}
+    directory. Note the example registers the provider via a \l{QDeclarativeExtensionPlugin}{plugin}
+    instead of registering it in the application \c main() function as shown above.
+
+
+    \section2 Asynchronous image loading
+
+    Image providers that support QImage loading automatically include support
+    for asychronous loading of images. To enable asynchronous loading for an
+    \l Image source, set \l Image::asynchronous to \c true. When this is enabled, 
+    the image request to the provider is run in a low priority thread,
+    allowing image loading to be executed in the background, and reducing the
+    performance impact on the user interface.
+
+    Asynchronous loading is not supported for image providers that provide
+    QPixmap rather than QImage values, as pixmaps can only be created in the
+    main thread. In this case, if \l {Image::}{asynchronous} is set to 
+    \c true, the value is ignored and the image is loaded
+    synchronously.
+   
+    \sa QDeclarativeEngine::addImageProvider()
+*/
+
+/*!
+    \enum QDeclarativeImageProvider::ImageType
+
+    Defines the type of image supported by this image provider.
 
-    \sa QDeclarativeEngine::addImageProvider(), {declarative/cppextensions/imageprovider}{ImageProvider example}
+    \value Image The Image Provider provides QImage images. The 
+        requestImage() method will be called for all image requests.
+    \value Pixmap The Image Provider provides QPixmap images. The 
+        requestPixmap() method will be called for all image requests.
 */
 
 /*!
-  Destroys the image provider.
- */
+    Creates an image provider that will provide images of the given \a type.
+*/
+QDeclarativeImageProvider::QDeclarativeImageProvider(ImageType type)
+    : d(new QDeclarativeImageProviderPrivate)
+{
+    d->type = type;
+}
+
+/*!
+   \internal
+*/
 QDeclarativeImageProvider::~QDeclarativeImageProvider()
 {
+    delete d;
 }
 
 /*!
-    \fn QImage QDeclarativeImageProvider::request(const QString &id, QSize *size, const QSize& requestedSize)
+    Returns the image type supported by this provider.
+*/
+QDeclarativeImageProvider::ImageType QDeclarativeImageProvider::imageType() const
+{
+    return d->type;
+}
 
-    Implement this method to return the image with \a id.
+/*!
+    Implement this method to return the image with \a id. The default 
+    implementation returns an empty image.
 
     If \a requestedSize is a valid size, the image returned should be of that size.
 
@@ -80,5 +187,36 @@ QDeclarativeImageProvider::~QDeclarativeImageProvider()
     \note this method may be called by multiple threads, so ensure the
     implementation of this method is reentrant.
 */
+QImage QDeclarativeImageProvider::requestImage(const QString &id, QSize *size, const QSize& requestedSize)
+{
+    Q_UNUSED(id);
+    Q_UNUSED(size);
+    Q_UNUSED(requestedSize);
+    if (d->type == Image)
+        qWarning("ImageProvider supports Image type but has not implemented requestImage()");
+    return QImage();
+}
+
+/*!
+    Implement this method to return the pixmap with \a id. The default
+    implementation returns an empty pixmap.
+
+    If \a requestedSize is a valid size, the image returned should be of that size.
+
+    In all cases, \a size must be set to the original size of the image.
+
+    \note this method may be called by multiple threads, so ensure the
+    implementation of this method is reentrant.
+*/
+QPixmap QDeclarativeImageProvider::requestPixmap(const QString &id, QSize *size, const QSize& requestedSize)
+{
+    Q_UNUSED(id);
+    Q_UNUSED(size);
+    Q_UNUSED(requestedSize);
+    if (d->type == Pixmap)
+        qWarning("ImageProvider supports Pixmap type but has not implemented requestPixmap()");
+    return QPixmap();
+}
 
 QT_END_NAMESPACE
+
diff --git a/src/declarative/qml/qdeclarativeimageprovider.h b/src/declarative/qml/qdeclarativeimageprovider.h
index cc9c9af..5a72943 100644
--- a/src/declarative/qml/qdeclarativeimageprovider.h
+++ b/src/declarative/qml/qdeclarativeimageprovider.h
@@ -43,6 +43,7 @@
 #define QDECLARATIVEIMAGEPROVIDER_H
 
 #include <QtGui/qimage.h>
+#include <QtGui/qpixmap.h>
 
 QT_BEGIN_HEADER
 
@@ -50,11 +51,26 @@ QT_BEGIN_NAMESPACE
 
 QT_MODULE(Declarative)
 
+class QDeclarativeImageProviderPrivate;
+
 class Q_DECLARATIVE_EXPORT QDeclarativeImageProvider
 {
 public:
+    enum ImageType {
+        Image,
+        Pixmap
+    };
+
+    QDeclarativeImageProvider(ImageType type);
     virtual ~QDeclarativeImageProvider();
-    virtual QImage request(const QString &id, QSize *size, const QSize& requestedSize) = 0;
+
+    ImageType imageType() const;
+
+    virtual QImage requestImage(const QString &id, QSize *size, const QSize& requestedSize);
+    virtual QPixmap requestPixmap(const QString &id, QSize *size, const QSize& requestedSize);
+
+private:
+    QDeclarativeImageProviderPrivate *d;
 };
 
 QT_END_NAMESPACE
diff --git a/src/declarative/util/qdeclarativepixmapcache.cpp b/src/declarative/util/qdeclarativepixmapcache.cpp
index fdc2455..3f496b3 100644
--- a/src/declarative/util/qdeclarativepixmapcache.cpp
+++ b/src/declarative/util/qdeclarativepixmapcache.cpp
@@ -736,6 +736,58 @@ void QDeclarativePixmapData::removeFromCache()
     }
 }
 
+static QDeclarativePixmapData* createPixmapDataSync(QDeclarativeEngine *engine, const QUrl &url, const QSize &requestSize, bool *ok)
+{
+    if (url.scheme() == QLatin1String("image")) {
+        QSize readSize;
+        QDeclarativeEnginePrivate *ep = QDeclarativeEnginePrivate::get(engine);
+        QDeclarativeImageProvider::ImageType imageType = ep->getImageProviderType(url);
+
+        switch (imageType) {
+            case QDeclarativeImageProvider::Image:
+            {
+                QImage image = ep->getImageFromProvider(url, &readSize, requestSize);
+                if (!image.isNull()) {
+                    *ok = true;
+                    return new QDeclarativePixmapData(url, QPixmap::fromImage(image), readSize, requestSize);
+                }
+            }
+            case QDeclarativeImageProvider::Pixmap:
+            {
+                QPixmap pixmap = ep->getPixmapFromProvider(url, &readSize, requestSize);
+                if (!pixmap.isNull()) {
+                    *ok = true;
+                    return new QDeclarativePixmapData(url, pixmap, readSize, requestSize);
+                }
+            }
+        }
+
+        // no matching provider, or provider has bad image type, or provider returned null image
+        return new QDeclarativePixmapData(url, requestSize,
+            QDeclarativePixmap::tr("Failed to get image from provider: %1").arg(url.toString()));
+    }
+
+    QString localFile = QDeclarativeEnginePrivate::urlToLocalFileOrQrc(url);
+    if (localFile.isEmpty()) 
+        return 0;
+
+    QFile f(localFile);
+    QSize readSize;
+    QString errorString;
+
+    if (f.open(QIODevice::ReadOnly)) {
+        QImage image;
+        if (readImage(url, &f, &image, &errorString, &readSize, requestSize)) {
+            *ok = true;
+            return new QDeclarativePixmapData(url, QPixmap::fromImage(image), readSize, requestSize);
+        }
+    } else {
+        errorString = QDeclarativePixmap::tr("Cannot open: %1").arg(url.toString());
+    }
+    return new QDeclarativePixmapData(url, requestSize, errorString);
+}
+
+
 struct QDeclarativePixmapNull {
     QUrl url;
     QPixmap pixmap;
@@ -893,27 +945,24 @@ void QDeclarativePixmap::load(QDeclarativeEngine *engine, const QUrl &url, const
     QHash<QDeclarativePixmapKey, QDeclarativePixmapData *>::Iterator iter = store->m_cache.find(key);
 
     if (iter == store->m_cache.end()) {
-        if (!async) {
-            QString localFile = QDeclarativeEnginePrivate::urlToLocalFileOrQrc(url);
-            if (!localFile.isEmpty()) {
-                QFile f(localFile);
-                QSize readSize;
-                QString errorString;
-
-                if (f.open(QIODevice::ReadOnly)) {
-                    QImage image;
-                    if (readImage(url, &f, &image, &errorString, &readSize, requestSize)) {
-                        d = new QDeclarativePixmapData(url, QPixmap::fromImage(image), readSize, requestSize);
-                        d->addToCache();
-                        return;
-                    } 
-                } else {
-                    errorString = tr("Cannot open: %1").arg(url.toString());
-                }
+        if (async) {
+            if (url.scheme() == QLatin1String("image") 
+                    && QDeclarativeEnginePrivate::get(engine)->getImageProviderType(url) == QDeclarativeImageProvider::Pixmap) {
+                qWarning().nospace() << "Pixmaps must be loaded synchronously, ignoring asynchronous property for Image with source: "
+                        << url.toString();
+                async = false;
+            }
+        }
 
-                d = new QDeclarativePixmapData(url, requestSize, errorString);
+        if (!async) {
+            bool ok = false;
+            d = createPixmapDataSync(engine, url, requestSize, &ok);
+            if (ok) {
+                d->addToCache();
                 return;
             }
+            if (d)  // loadable, but encountered error while loading
+                return;
         } 
 
         if (!engine)