RFR: 8294156: Demo positioning of multiple test windows [v2]

[Alexey Ivanov]

On Wed, 13 Sep 2023 18:50:54 GMT, Alexey Ivanov <aivanov at openjdk.org> wrote:

>> The manual test frame does not provide any layout managers for test windows, the user has to implement one. This demonstrates how to position a several test UI windows.
>> 
>> We may include some implementations into the manual test framework in the future.
>> 
>> **This PR is not meant to be integrated.** It just demonstrates the feature of adding multiple test windows to `PassFailJFrame` which is reviewed in #15665.
>> 
>> To play around, you can checkout the PR branch using the commands that bots add.
>> 
>> Path to the tests: `test/jdk/java/awt/Window/8294156`.
>> 
>> Alternatively, you can checkout directly from my fork:
>> 
>> 
>> git fetch https://github.com/aivanov-jdk/jdk.git demo-manyTestWindows:demo-manyTestWindows
>> git checkout demo-manyTestWindows
>
> Alexey Ivanov has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8294156: Additional layouts for vertically positioned test windows

The `ThreeWindowRows` test from the demo set creates 8 test windows which are laid out in three rows below the instructions window: the first two rows contain 3 windows, the last row contains 2 windows. The instructions window is moved upwards, it's on the zeroth row. The entire set is centred on the screen.

![ThreeWindowRows: instruction window followed by three rows of test UI windows](https://github.com/openjdk/jdk/assets/70774172/653a9689-dd09-4424-a510-063cca8260d7)

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PR Comment: https://git.openjdk.org/jdk/pull/15721#issuecomment-1718154967