RFR: 8301302: Platform preferences API [v18]

[Michael Strauß]

On Tue, 31 Oct 2023 22:33:00 GMT, Nir Lisker <nlisker at openjdk.org> wrote:

>> Michael Strauß has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - formatting
>>  - Javadoc change
>
> modules/javafx.graphics/src/main/java/javafx/application/Platform.java line 636:
> 
>> 634:          *         if no mapping exists for the specified key
>> 635:          */
>> 636:         Optional<Double> getDouble(String key);
> 
> I'm a bit confused about this and similar methods. Several points:
> 
> 1. There is no value that is a `Double`, and also no `Paint`, so I'm not sure what these are for considering that list gives all possible valid entries.
> 
> 2. If the list of keys in the table is fully known, wouldn't an enum make more sense and be more safe than of a `String`?

1. There is no `Double` value now, but there might be in the future. For exampe, the API may expose system-provided double-click times, or it may expose information about the dimensions of system decorations. As for `Paint`, it might be conceivable that a platform would expose color gradients.

2. The list is only fully known for the three listed platforms, but it's unknown for other platforms. Using an enum key instead of a string key is certainly possible, but then we'd be hard-coding platform-specific constants into the core of JavaFX. You might argue that providing a list of supported keys isn't really all that different from using a language feature like enums to represent the constants. Using platform-specific preferences requires a deep understanding of the platform in any case, and is not something application developers should rely on regularly. Instead, they should be using the common subset of well-known preferences, which is easily accessible via the properties on the `Platform` class.

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PR Review Comment: https://git.openjdk.org/jfx/pull/1014#discussion_r1378356218