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Re: FengAndy@aol.com

From: Jim Luther <luther.j@apple.com>
Date: Wed, 17 Mar 2004 15:23:50 -0800
Message-Id: <25E4E884-786A-11D8-80BA-000A95DC65E0@apple.com>
Cc: FengAndy@aol.com
To: w3c-dist-auth@w3.org

Windows XP uses a completely different scheme for displaying  
thumbnails. You'd need to talk to someone at Microsoft about how it  
works.

- Jim (at Apple, not Microsoft :)

> Jim,
>
> I noticed that Windows XP could display the thumbnail for iDisk stored  
> pictures. However, it's not be able to display thumbnails.
>
> Any explanation?
>
> Andy
>
>> In a message dated 3/17/2004 1:46:11 PM Pacific Standard Time,  
>> luther.j@apple.com writes:
>>
>> On a Macintosh, thumbnails icons for directories are stored in a 
>> special file inside the directory (Mac OS 8 through 9 and Mac OS X  
>> use 
>> different techniques for that file). Thumbnails icons for files are 
>> stored in a file's resource fork (the Macintosh file system supports 
>> two file forks -- See 
>> <http://developer.apple.com/documentation/mac/Files/Files-14.html>).
>>
>> To store a file's data fork and the file's resource fork and other 
>> Macintosh-specific metadata on volume formats (like WebDAV) which  
>> don't 
>> support Macintosh-style resources forks or metadata, the file is  
>> stored 
>> in AppleDouble format (it's funny but the only place I can find the 
>> AppleDouble documentation isn't on Apple web site -- it's at 
>> <http://www.lazerware.com/formats/Specs/AppleSingle_AppleDouble.pdf>. 
>> The AppleDouble formatted file is stored as two files. The data for  
>> the 
>> file is stored in the "AppleDouble Data file" which has the file's 
>> name. The resource fork and other Macintosh-specific metadata is  
>> stored 
>> in the "AppleDouble Header file" which has the file's name with the 
>> characters "._" prepended.
>>
>> So, if you look at a WebDAV server that has files stored by Mac OS X 
>> clients, you'll probably see files with names beginning with "._" -- 
>> that's where the thumbnail icons (if any) are stored.
>>
>> If a non-Macintosh client wanted to display those icons, it would be  
>> a 
>> lot of work. That client would have to know how to:
>>
>> 1 - Parse the AppleDouble Header file to get the Macintosh Finder 
>> information (the metadata which contains a flag indicating the  
>> presence 
>> of a custom thumbnail icon) and the resource fork.
>>
>> 2 - Interpret the resource fork to get to the custom icon resources 
>> (see 
>> http://developer.apple.com/documentation/mac/MoreToolbox/MoreToolbox
>> -99.html for the resoruce file format).
>>
>> 3 - Display the icon resources (they are bitmaps (see 
>> http://developer.apple.com/documentation/mac/Toolbox/Toolbox 
>> -448.html), 
>> 'icns' resources (see 
>> http://developer.apple.com/documentation/Carbon/Conceptual/
>> Icon_Service_nd_Utilities/02concepts/chapter_2_section_4.html), or in 
>> PICT format (see 
>> http://developer.apple.com/documentation/mac/QuickDraw/QuickDraw
>> -458.html) -- they aren't jpeg or gif).
>>
>> So... a bunch of work just for thumbnails.
>>
>> - Jim Luther
>>
>> On Mar 17, 2004, at 11:23 AM, Julian Reschke wrote:
>>
>> >
>> > FengAndy@aol.com wrote:
>> >> Folks,
>> >>  Have anyone tried to enable thumbnails via WebDAV clients?  
>> Apple's 
>> >> iDisk enables such features. All other WebDAV clients don't seem  
>> to 
>> >> have such support. For example, in Windows, you could not select a 
>> >> WebFolder to have a thumbnail view.
>> >>  Any suggestion? Thanks in advance.
>> >
>> > There's no specific support for that in WebDAV. Do you know what 
>> > Apple's iDisk is doing here?
>> >
>> > Regards, Julian
>> >
>> >
>> > --
>> > <green/>bytes GmbH -- http://www.greenbytes.de -- tel:+492512807760
Received on Wednesday, 17 March 2004 18:24:39 UTC

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