internal static async Task <NSDraggingItem[]> CreateNativeDragDropData(
DataPackageView data,
Point startPoint)
{
NSDraggingItem draggingItem;
var items = new List <NSDraggingItem>();
double maxFrameDimension = 300.0; // May be adjusted
var defaultFrameRect = new CoreGraphics.CGRect(startPoint.X, startPoint.Y, 100, 30);
/* Note that NSDraggingItems are required by the BeginDraggingSession methods.
* Therefore, that is what is constructed here instead of pasteboard items.
*
* For several types such as NSString or NSImage, they implement the INSPasteboardWriting interface and
* can therefore be used to directly construct an NSDraggingItem.
* However, for other types (such as HTML) the full pasteboard item must be constructed first defining
* both its type and string content.
*
* The dragging frame is used to represent the visual of the item being dragged. This could be a
* preview of the image or sample text. At minimum, macOS requires the DraggingFrame property of the
* NSDraggingItem to be set with a CGRect or the app will crash. It is however better to set both
* the frame bounds and content at the same time with .SetDraggingFrame(). For caveats see:
* https://developer.apple.com/documentation/appkit/nsdraggingitem/1528746-setdraggingframe
*
* Because Uno does not currently support the DragUI, this code only generates a real drag visual
* for images where a visual is already defined. For other types such as text, no visual will be
* generated. In the future, when DragUI and its corresponding image is supported, this can change.
*
*/
if (data?.Contains(StandardDataFormats.Bitmap) ?? false)
{
NSImage?image = null;
using (var stream = (await(await data.GetBitmapAsync()).OpenReadAsync()).AsStream())
{
if (stream != null)
{
using (var ms = new MemoryStream())
{
await stream.CopyToAsync(ms);
ms.Flush();
ms.Position = 0;
image = NSImage.FromStream(ms);
}
}
}
if (image != null)
{
draggingItem = new NSDraggingItem(image);
// For an NSImage, we will use the image itself as the dragging visual.
// The visual should be no larger than the max dimension setting and is therefore scaled.
NSBitmapImageRep rep = new NSBitmapImageRep(image.CGImage);
int width = (int)rep.PixelsWide;
int height = (int)rep.PixelsHigh;
double scale = maxFrameDimension / Math.Max(width, height);
// Dragging frame must be set
draggingItem.SetDraggingFrame(
new CoreGraphics.CGRect(startPoint.X, startPoint.Y, width * scale, height * scale),
image);
items.Add(draggingItem);
}
}
if (data?.Contains(StandardDataFormats.Html) ?? false)
{
var html = await data.GetHtmlFormatAsync();
if (!string.IsNullOrEmpty(html))
{
var pasteboardItem = new NSPasteboardItem();
pasteboardItem.SetStringForType(html, NSPasteboard.NSPasteboardTypeHTML);
draggingItem = new NSDraggingItem(pasteboardItem);
draggingItem.DraggingFrame = defaultFrameRect; // Must be set
items.Add(draggingItem);
}
}
if (data?.Contains(StandardDataFormats.Rtf) ?? false)
{
var rtf = await data.GetRtfAsync();
if (!string.IsNullOrEmpty(rtf))
{
// Use `NSPasteboardTypeRTF` instead of `NSPasteboardTypeRTFD` for max compatibility
var pasteboardItem = new NSPasteboardItem();
pasteboardItem.SetStringForType(rtf, NSPasteboard.NSPasteboardTypeRTF);
draggingItem = new NSDraggingItem(pasteboardItem);
draggingItem.DraggingFrame = defaultFrameRect; // Must be set
items.Add(draggingItem);
}
}
if (data?.Contains(StandardDataFormats.StorageItems) ?? false)
{
var storageItems = await data.GetStorageItemsAsync();
if (storageItems.Count > 0)
{
// Not currently supported
}
}
if (data?.Contains(StandardDataFormats.Text) ?? false)
{
var text = await data.GetTextAsync();
if (!string.IsNullOrEmpty(text))
{
draggingItem = new NSDraggingItem((NSString)text);
draggingItem.DraggingFrame = defaultFrameRect; // Must be set
items.Add(draggingItem);
}
}
if (data != null)
{
var uri = DataPackage.CombineUri(
data.Contains(StandardDataFormats.WebLink) ? (await data.GetWebLinkAsync()).ToString() : null,
data.Contains(StandardDataFormats.ApplicationLink) ? (await data.GetApplicationLinkAsync()).ToString() : null,
data.Contains(StandardDataFormats.Uri) ? (await data.GetUriAsync()).ToString() : null);
if (string.IsNullOrEmpty(uri) == false)
{
draggingItem = new NSDraggingItem(new NSUrl(uri));
draggingItem.DraggingFrame = defaultFrameRect; // Must be set
items.Add(draggingItem);
}
}
return(items.ToArray());
}
