MICROSOFT_PRESS_EBOOK_PROGRAMMING_WINDOWS_8_APPS_WITH_HTML_CSS_AND_JAVASCRIPT_PDF

When sharing an image, don't forget to set the thumbnail for the DataPackage
var streamReference =
Windows.Storage.Streams.RandomAccessStreamReference.createFromFile(imageFile);
request.data.properties.thumbnail = streamReference;
request.data.setDataProvider(
Windows.ApplicationModel.DataTransfer.StandardDataFormats.bitmap,
onDeferredImageRequested);
As indicated in the comments, it’s a really good idea to provide a thumbnail with delayed rendering
so the target app has something to show the user. Then, when the target needs the full data, the data
provider function gets called—in this case, onDeferredImageRequsted:
function onDeferredImageRequested(request) {
if (imageFile) {
// Here we provide updated Bitmap data using delayed rendering
var deferral = request.getDeferral();
var imageDecoder, inMemoryStream;
}
}
imageFile.openAsync(Windows.Storage.FileAccessMode.read).then(function (stream) {
// Decode the image
return Windows.Graphics.Imaging.BitmapDecoder.createAsync(stream);
}).then(function (decoder) {
// Re-encode the image at 50% width and height
inMemoryStream = new Windows.Storage.Streams.InMemoryRandomAccessStream();
imageDecoder = decoder;
return Windows.Graphics.Imaging.BitmapEncoder.createForTranscodingAsync(
inMemoryStream, decoder);
}).then(function (encoder) {
encoder.bitmapTransform.scaledWidth = imageDecoder.orientedPixelWidth * 0.5;
encoder.bitmapTransform.scaledHeight = imageDecoder.orientedPixelHeight * 0.5;
return encoder.flushAsync();
}).done(function () {
var streamReference = Windows.Storage.Streams.RandomAccessStreamReference
.createFromStream(inMemoryStream);
request.setData(streamReference);
deferral.complete();
}, function (e) {
// didn't succeed, but we still need to release the deferral to avoid
//a hang in the target app
deferral.complete();
});
Note that this function receives a simplified hybrid of the DataRequest and DataPackage objects: a
DataProviderRequest that contains deadline and formatId properties, a getDeferral method, and a
setData method through which you provide the data that matched formatId. The deadline property, as
you can guess, is the same as what the datarequested handler might have stored in the DataRequest
object.
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