How does OSX tell what app to open when you double click a file?

[David V Glasgow]

Hah! The devil is in the last line. (not to mention that the criteria don’t seem to match what actually happens)

> On 8 Aug 2019, at 12:34 pm, Paul Dupuis via use-livecode <use-livecode at lists.runrev.com> wrote:
> 
> On 8/6/2019 10:10 PM, Mark Waddingham via use-livecode wrote:
>> On 2019-08-06 23:59, Paul Dupuis via use-livecode wrote:
>>> For example, if you drag installed 5 apps, APP1, 2, 3, etc, that all
>>> had a info.plist defintion for a .xyz file extension onto a virgin OSX
>>> system out of the box and then double-clicked a .wyz file, which of
>>> the 5 would open?
>> 
>> I *think* the answer to this question probably lies here:
>> 
>> https://developer.apple.com/library/archive/documentation/Carbon/Conceptual/LaunchServicesConcepts/LSCConcepts/LSCConcepts.html#//apple_ref/doc/uid/TP30000999-CH202-TP9 
>> 
>> The sections on 'Application Registration' and 'Preferred Applications' are probably the most pertinent - although it isn't entirely clear how the two mechanisms co-exist: registration suggests the 'most recent' modification time wise app is stored against a file kind, but preferred applications suggests that multiple apps are stored but the newest CFBundleVersion wise is chosen.
>> 
>> Warmest Regards,
>> 
>> Mark.
>> 
> 
> Thank you again!
> 
> This section of that web page was exactly what I was looking for:
> 
> 
>     Preferred Application for a Document
> 
> For individual document files (whether specified by a file-system reference or a URL with scheme |file|), the criteria are as follows:
> 
> 1.
> 
>   If the user has specified an explicit binding for the document (or
>   for the entire document type to which it belongs), the preferred
>   application is the one the user has specified.
> 
> 2.
> 
>   If the document has a filename extension (or if one has been
>   specified as a parameter to |LSGetApplicationForInfo|), find all
>   applications in the Launch Services database that claim to accept
>   documents with that extension.
> 
> 3.
> 
>   If the document carries a four-character file type (or if one has
>   been specified as a parameter), find all applications that claim to
>   accept files of that type.
> 
> 4.
> 
>   If more than one application has been found as a result of steps
>   2–3, apply the following criteria in the order shown:
> 
>    1.
> 
>       If the document carries a four-character creator signature (or
>       if one has been specified as a parameter), give preference to
>       any application that claims to accept documents with that
>       signature (typically the application to which the signature
>       belongs).
> 
>    2.
> 
>       Give preference to native OS X applications over those that run
>       in the Classic emulation environment.
> 
>    3.
> 
>       Give preference to applications residing on the boot volume over
>       those residing on other file-system volumes.
> 
>    4.
> 
>       Give preference to applications residing on a local volume over
>       those residing on a remote volume.
> 
>    5.
> 
>       If two or more versions of the same application have been found,
>       give preference to the one with the latest version number as
>       identified by |CFBundleVersion
>       <https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html#//apple_ref/doc/plist/info/CFBundleVersion>|.
> 
> If two or more candidate applications remain after all of the foregoing criteria have been applied, Launch Services chooses one of the remaining applications in an unspecified manner.
> 
> 
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