/*

     File: DragDropImageView.m 

 Abstract: Custom subclass of NSImageView with support for drag and drop operations. 

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 */

#import "DragDropImageView.h"

@implementation DragDropImageView

NSString *kPrivateDragUTI = @"com.yourcompany.cocoadraganddrop";

- (id)initWithCoder:(NSCoder *)coder

{

    /*------------------------------------------------------

        Init method called for Interface Builder objects

    --------------------------------------------------------*/

    self=[super initWithCoder:coder];

    if ( self ) {

            //register for all the image types we can display

        [self registerForDraggedTypes:[NSImage imagePasteboardTypes]];

    }

    return self;

}

#pragma mark - Destination Operations

- (NSDragOperation)draggingEntered:(id <NSDraggingInfo>)sender

{

    /*------------------------------------------------------

        method called whenever a drag enters our drop zone

     --------------------------------------------------------*/

            // Check if the pasteboard contains image data and source/user wants it copied

    if ( [NSImage canInitWithPasteboard:[sender draggingPasteboard]] &&

             [sender draggingSourceOperationMask] &

             NSDragOperationCopy ) {

            //highlight our drop zone

        highlight=YES;

        [self setNeedsDisplay: YES];

            /* When an image from one window is dragged over another, we want to resize the dragging item to

             * preview the size of the image as it would appear if the user dropped it in. */

        [sender enumerateDraggingItemsWithOptions:NSDraggingItemEnumerationConcurrent 

            forView:self

            classes:[NSArray arrayWithObject:[NSPasteboardItem class]] 

            searchOptions:nil 

            usingBlock:^(NSDraggingItem *draggingItem, NSInteger idx, BOOL *stop) {

                    /* Only resize a fragging item if it originated from one of our windows.  To do this,

                     * we declare a custom UTI that will only be assigned to dragging items we created.  Here

                     * we check if the dragging item can represent our custom UTI.  If it can't we stop. */

                if ( ![[[draggingItem item] types] containsObject:kPrivateDragUTI] ) {

                    *stop = YES;

                } else {

                        /* In order for the dragging item to actually resize, we have to reset its contents.

                         * The frame is going to be the destination view's bounds.  (Coordinates are local 

                         * to the destination view here).

                         * For the contents, we'll grab the old contents and use those again.  If you wanted

                         * to perform other modifications in addition to the resize you could do that here. */

                    [draggingItem setDraggingFrame:self.bounds contents:[[[draggingItem imageComponents] objectAtIndex:0] contents]];

                }

            }];

        //accept data as a copy operation

        return NSDragOperationCopy;

    }

    return NSDragOperationNone;

}

- (void)draggingExited:(id <NSDraggingInfo>)sender

{

    /*------------------------------------------------------

       method called whenever a drag exits our drop zone

    --------------------------------------------------------*/

        //remove highlight of the drop zone

    highlight=NO;

    [self setNeedsDisplay: YES];

}

-(void)drawRect:(NSRect)rect

{

    /*------------------------------------------------------

        draw method is overridden to do drop highlighing

    --------------------------------------------------------*/

        //do the usual draw operation to display the image

    [super drawRect:rect];

    if ( highlight ) {

            //highlight by overlaying a gray border

        [[NSColor grayColor] set];

        [NSBezierPath setDefaultLineWidth: 5];

        [NSBezierPath strokeRect: rect];

    }

}

- (BOOL)prepareForDragOperation:(id <NSDraggingInfo>)sender

{

    /*------------------------------------------------------

        method to determine if we can accept the drop

    --------------------------------------------------------*/

        //finished with the drag so remove any highlighting

    highlight=NO;

    [self setNeedsDisplay: YES];

        //check to see if we can accept the data

    return [NSImage canInitWithPasteboard: [sender draggingPasteboard]];

} 

- (BOOL)performDragOperation:(id <NSDraggingInfo>)sender

{

    /*------------------------------------------------------

        method that should handle the drop data

    --------------------------------------------------------*/

    if ( [sender draggingSource] != self ) {

        NSURL* fileURL;

            //set the image using the best representation we can get from the pasteboard

        if([NSImage canInitWithPasteboard: [sender draggingPasteboard]]) {

            NSImage *newImage = [[NSImage alloc] initWithPasteboard: [sender draggingPasteboard]];

            [self setImage:newImage];

            [newImage release];

        }

            //if the drag comes from a file, set the window title to the filename

        fileURL=[NSURL URLFromPasteboard: [sender draggingPasteboard]];

        [[self window] setTitle: fileURL!=NULL ? [fileURL absoluteString] : @"(no name)"];

    }

    return YES;

}

- (NSRect)windowWillUseStandardFrame:(NSWindow *)window defaultFrame:(NSRect)newFrame;

{

    /*------------------------------------------------------

       delegate operation to set the standard window frame

    --------------------------------------------------------*/

        //get window frame size

    NSRect ContentRect=self.window.frame;

        //set it to the image frame size

    ContentRect.size=[[self image] size];

    return [NSWindow frameRectForContentRect:ContentRect styleMask: [window styleMask]];

};

#pragma mark - Source Operations

- (void)mouseDown:(NSEvent*)event

{

    /*------------------------------------------------------

        catch mouse down events in order to start drag

    --------------------------------------------------------*/

    /* Dragging operation occur within the context of a special pasteboard (NSDragPboard).

     * All items written or read from a pasteboard must conform to NSPasteboardWriting or 

     * NSPasteboardReading respectively.  NSPasteboardItem implements both these protocols

     * and is as a container for any object that can be serialized to NSData. */

    NSPasteboardItem *pbItem = [NSPasteboardItem new];

        /* Our pasteboard item will support public.tiff, public.pdf, and our custom UTI (see comment in -draggingEntered)

         * representations of our data (the image).  Rather than compute both of these representations now, promise that 

         * we will provide either of these representations when asked.  When a receiver wants our data in one of the above 

         * representations, we'll get a call to  the NSPasteboardItemDataProvider protocol method –pasteboard:item:provideDataForType:. */

    [pbItem setDataProvider:self forTypes:[NSArray arrayWithObjects:NSPasteboardTypeTIFF, NSPasteboardTypePDF, kPrivateDragUTI, nil]];

        //create a new NSDraggingItem with our pasteboard item.

    NSDraggingItem *dragItem = [[NSDraggingItem alloc] initWithPasteboardWriter:pbItem];

    [pbItem release];

        /* The coordinates of the dragging frame are relative to our view.  Setting them to our view's bounds will cause the drag image

         * to be the same size as our view.  Alternatively, you can set the draggingFrame to an NSRect that is the size of the image in

         * the view but this can cause the dragged image to not line up with the mouse if the actual image is smaller than the size of the

         * our view. */

    NSRect draggingRect = self.bounds;

        /* While our dragging item is represented by an image, this image can be made up of multiple images which

         * are automatically composited together in painting order.  However, since we are only dragging a single

         * item composed of a single image, we can use the convince method below. For a more complex example

         * please see the MultiPhotoFrame sample. */

    [dragItem setDraggingFrame:draggingRect contents:[self image]];

        //create a dragging session with our drag item and ourself as the source.

    NSDraggingSession *draggingSession = [self beginDraggingSessionWithItems:[NSArray arrayWithObject:[dragItem autorelease]] event:event source:self];

        //causes the dragging item to slide back to the source if the drag fails.

    draggingSession.animatesToStartingPositionsOnCancelOrFail = YES;

    draggingSession.draggingFormation = NSDraggingFormationNone;

}

- (NSDragOperation)draggingSession:(NSDraggingSession *)session sourceOperationMaskForDraggingContext:(NSDraggingContext)context

{

    /*------------------------------------------------------

     NSDraggingSource protocol method.  Returns the types of operations allowed in a certain context.

     --------------------------------------------------------*/

    switch (context) {

        case NSDraggingContextOutsideApplication:

            return NSDragOperationCopy;

            //by using this fall through pattern, we will remain compatible if the contexts get more precise in the future.

        case NSDraggingContextWithinApplication:

        default:

            return NSDragOperationCopy;

            break;

    }

}

- (BOOL)acceptsFirstMouse:(NSEvent *)event 

{

    /*------------------------------------------------------

        accept activation click as click in window

    --------------------------------------------------------*/

        //so source doesn't have to be the active window

    return YES;

}

- (void)pasteboard:(NSPasteboard *)sender item:(NSPasteboardItem *)item provideDataForType:(NSString *)type

{

    /*------------------------------------------------------

        method called by pasteboard to support promised 

        drag types.

    --------------------------------------------------------*/

        //sender has accepted the drag and now we need to send the data for the type we promised

    if ( [type compare: NSPasteboardTypeTIFF] == NSOrderedSame ) {

            //set data for TIFF type on the pasteboard as requested

        [sender setData:[[self image] TIFFRepresentation] forType:NSPasteboardTypeTIFF];

    } else if ( [type compare: NSPasteboardTypePDF] == NSOrderedSame ) {

            //set data for PDF type on the pasteboard as requested

        [sender setData:[self dataWithPDFInsideRect:[self bounds]] forType:NSPasteboardTypePDF];

    }

}

@end