Added support in qimagereader to base plugin selection on stream content

Reviewed-by: Trond

2 files changed, 49 insertions, 10 deletions

diff --git a/src/gui/image/qimagereader.cpp b/src/gui/image/qimagereader.cpp
index 41df852..5cd768f 100644
--- a/src/gui/image/qimagereader.cpp
+++ b/src/gui/image/qimagereader.cpp
@@ -195,7 +195,9 @@ static const _qt_BuiltInFormatStruct _qt_BuiltInFormats[] = {
 };
 
 static QImageIOHandler *createReadHandlerHelper(QIODevice *device,
-                                                const QByteArray &format, bool autoDetectImageFormat)
+                                                const QByteArray &format,
+                                                bool autoDetectImageFormat,
+                                                bool ignoresFormatAndExtension)
 {
     if (!autoDetectImageFormat && format.isEmpty())
         return 0;
@@ -217,7 +219,7 @@ static QImageIOHandler *createReadHandlerHelper(QIODevice *device,
 
 #if !defined (QT_NO_LIBRARY) && !defined(QT_NO_SETTINGS)
     int suffixPluginIndex = -1;
-    if (device && format.isEmpty() && autoDetectImageFormat) {
+    if (device && format.isEmpty() && autoDetectImageFormat && !ignoresFormatAndExtension) {
         // if there's no format, see if \a device is a file, and if so, find
         // the file suffix and find support for that format among our plugins.
         // this allows plugins to override our built-in handlers.
@@ -241,6 +243,9 @@ static QImageIOHandler *createReadHandlerHelper(QIODevice *device,
 
     QByteArray testFormat = !form.isEmpty() ? form : suffix;
 
+    if (ignoresFormatAndExtension)
+        testFormat = QByteArray();
+
 #if !defined (QT_NO_LIBRARY) && !defined(QT_NO_SETTINGS)
     if (suffixPluginIndex != -1) {
         // check if the plugin that claims support for this format can load
@@ -258,7 +263,7 @@ static QImageIOHandler *createReadHandlerHelper(QIODevice *device,
             device->seek(pos);
     }
 
-    if (!handler && !testFormat.isEmpty() && autoDetectImageFormat) {
+    if (!handler && !testFormat.isEmpty() && autoDetectImageFormat && !ignoresFormatAndExtension) {
         // check if any plugin supports the format (they are not allowed to
         // read from the device yet).
         const qint64 pos = device ? device->pos() : 0;
@@ -315,7 +320,7 @@ static QImageIOHandler *createReadHandlerHelper(QIODevice *device,
     }
 
 #if !defined (QT_NO_LIBRARY) && !defined(QT_NO_SETTINGS)
-    if (!handler && autoDetectImageFormat) {
+    if (!handler && (autoDetectImageFormat || ignoresFormatAndExtension)) {
         // check if any of our plugins recognize the file from its contents.
         const qint64 pos = device ? device->pos() : 0;
         for (int i = 0; i < keys.size(); ++i) {
@@ -335,7 +340,7 @@ static QImageIOHandler *createReadHandlerHelper(QIODevice *device,
     }
 #endif
 
-    if (!handler && autoDetectImageFormat) {
+    if (!handler && (autoDetectImageFormat || ignoresFormatAndExtension)) {
         // check if any of our built-in handlers recognize the file from its
         // contents.
         int currentFormat = 0;
@@ -434,6 +439,7 @@ public:
     // device
     QByteArray format;
     bool autoDetectImageFormat;
+    bool ignoresFormatAndExtension;
     QIODevice *device;
     bool deleteDevice;
     QImageIOHandler *handler;
@@ -458,7 +464,7 @@ public:
     \internal
 */
 QImageReaderPrivate::QImageReaderPrivate(QImageReader *qq)
-    : autoDetectImageFormat(true)
+    : autoDetectImageFormat(true), ignoresFormatAndExtension(false)
 {
     device = 0;
     deleteDevice = false;
@@ -522,7 +528,7 @@ bool QImageReaderPrivate::initHandler()
     }
 
     // assign a handler
-    if (!handler && (handler = createReadHandlerHelper(device, format, autoDetectImageFormat)) == 0) {
+    if (!handler && (handler = createReadHandlerHelper(device, format, autoDetectImageFormat, ignoresFormatAndExtension)) == 0) {
         imageReaderError = QImageReader::UnsupportedFormatError;
         errorString = QLatin1String(QT_TRANSLATE_NOOP(QImageReader, "Unsupported image format"));
         return false;
@@ -664,7 +670,7 @@ QByteArray QImageReader::format() const
     \o Finally, if all above approaches fail, QImageReader will report failure
     when trying to read the image.
 
-    \endlist    
+    \endlist
 
     By disabling image format autodetection, QImageReader will only query the
     plugins and built-in handlers based on the format string (i.e., no file
@@ -681,13 +687,43 @@ void QImageReader::setAutoDetectImageFormat(bool enabled)
     Returns true if image format autodetection is enabled on this image
     reader; otherwise returns false. By default, autodetection is enabled.
 
-    \sa setAutoDetectImageFormat()    
+    \sa setAutoDetectImageFormat()
 */
 bool QImageReader::autoDetectImageFormat() const
 {
     return d->autoDetectImageFormat;
 }
 
+
+/*!
+
+    Specifies that the image reader should decide which plugin to use
+    solely based on the contents in the datastream.
+
+    Setting this flag means that all image plugins gets loaded. Each
+    plugin will read the first bytes in the image data and decide if
+    the plugin is compatible or not.
+
+    This also disables auto detecting image format.
+*/
+
+void QImageReader::setDecideFormatFromContent(bool ignored)
+{
+    d->ignoresFormatAndExtension = ignored;
+}
+
+
+/*!
+    Returns wether the image reader should decide which plugin to use
+    sloley based on the contents of the datastream
+*/
+
+bool QImageReader::decideFormatFromContent() const
+{
+    return d->ignoresFormatAndExtension;
+}
+
+
 /*!
     Sets QImageReader's device to \a device. If a device has already
     been set, the old device is removed from QImageReader and is
@@ -1309,7 +1345,7 @@ QByteArray QImageReader::imageFormat(const QString &fileName)
 QByteArray QImageReader::imageFormat(QIODevice *device)
 {
     QByteArray format;
-    QImageIOHandler *handler = createReadHandlerHelper(device, format, /* autoDetectImageFormat = */ true);
+    QImageIOHandler *handler = createReadHandlerHelper(device, format, /* autoDetectImageFormat = */ true, false);
     if (handler) {
         if (handler->canRead())
             format = handler->format();
diff --git a/src/gui/image/qimagereader.h b/src/gui/image/qimagereader.h
index 86031ec..11affb8 100644
--- a/src/gui/image/qimagereader.h
+++ b/src/gui/image/qimagereader.h
@@ -81,6 +81,9 @@ public:
     void setAutoDetectImageFormat(bool enabled);
     bool autoDetectImageFormat() const;
 
+    void setDecideFormatFromContent(bool ignored);
+    bool decideFormatFromContent() const;
+
     void setDevice(QIODevice *device);
     QIODevice *device() const;