//  DraggableScrollView.h

//  Copyright (c) 2003, Apple Computer, Inc. All rights reserved.

// See legal notice below.

#import "DraggableScrollView.h"

@implementation DraggableScrollView

#pragma mark PRIVATE CLASS METHODS

//  dragCursor -- Return a cursor which hints that the user can drag.

//  FIXME: A hand would be better than this pointing finger.

+ (NSCursor *) dragCursor

{

    static NSCursor *openHandCursor = nil;

    if (openHandCursor == nil)

    {

        NSImage     *image;

        image = [NSImage imageNamed: @"fingerCursor"];

        openHandCursor = [[NSCursor alloc] initWithImage: image

            hotSpot: NSMakePoint (8, 8)]; // guess that the center is good

    }

    return openHandCursor;

}

#pragma mark PRIVATE INSTANCE METHODS

//  canScroll -- Return YES if the user could scroll.

- (BOOL) canScroll

{

    if ([[self documentView] frame].size.height > [self documentVisibleRect].size.height)

        return YES;

    if ([[self documentView] frame].size.width > [self documentVisibleRect].size.width)

        return YES;

    return NO;

}

#pragma mark PUBLIC INSTANCE METHODS -- OVERRIDES FROM NSScrolLView

//  tile -- Override to update the document cursor.

- (void) tile

{

    [super tile];

    //  If the user can scroll right now, make our document cursor reflect that.

    if ([self canScroll])

        [self setDocumentCursor: [[self class] dragCursor]];

    else

        [self setDocumentCursor: [NSCursor arrowCursor]];

}

#pragma mark PUBLIC INSTANCE METHODS

//  dragDocumentWithMouseDown: -- Given a mousedown event, which should be in

//  our document view, track the mouse to let the user drag the document.

- (BOOL) dragDocumentWithMouseDown: (NSEvent *) theEvent // RETURN: YES => user dragged (not clicked)

{

    NSPoint         initialLocation;

    NSRect          visibleRect;

    BOOL            keepGoing;

    BOOL            result = NO;

    initialLocation = [theEvent locationInWindow];

    visibleRect = [[self documentView] visibleRect];

    keepGoing = YES;

    while (keepGoing)

    {

        theEvent = [[self window] nextEventMatchingMask: NSLeftMouseUpMask | NSLeftMouseDraggedMask];

        switch ([theEvent type])

        {

            case NSLeftMouseDragged:

            {

                NSPoint newLocation;

                NSRect  newVisibleRect;

                float   xDelta, yDelta;

                newLocation = [theEvent locationInWindow];

                xDelta = initialLocation.x - newLocation.x;

                yDelta = initialLocation.y - newLocation.y;

                //  This was an amusing bug: without checking for flipped,

                //  you could drag up, and the document would sometimes move down!

                if ([[self documentView] isFlipped])

                    yDelta = -yDelta;

                //  If they drag MORE than one pixel, consider it a drag

                if ( (abs (xDelta) > 1) || (abs (yDelta) > 1) )

                    result = YES;

                newVisibleRect = NSOffsetRect (visibleRect, xDelta, yDelta);

                [[self documentView] scrollRectToVisible: newVisibleRect];

            }

            break;

            case NSLeftMouseUp:

                keepGoing = NO;

                break;

            default:

                /* Ignore any other kind of event. */

                break;

        }                               // end of switch (event type)

    }                                   // end of mouse-tracking loop

    return result;

}

@end

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