RFR: 8346281: [Windows] RenderScale doesn't update to HiDPI changes

[Andy Goryachev]

On Mon, 23 Dec 2024 10:51:39 GMT, Jose Pereda <jpereda at openjdk.org> wrote:

> This PR adds the missing native implementation for Windows `GlassWindow::HandleDPIEvent`, to notify the (Java) window when there is a DPI change event, which can happen when the user changes the resolution of the screen (via Settings -> System -> Display -> scale), while the JavaFX application is running.
> 
> When such `WM_DPICHANGED` event happens, `GlassWindow::HandleDPIEvent` notifies the (Java) window, which changes its platform scale via `Window::notifyScaleChanged`, and `GlassScreen::HandleDisplayChange();` is needed too, to update the platform scale of the screen where the window is at as well.
> 
> There are no tests added to this PR, since these would require manual intervention to change the display. In any case, the test case added to the [issue](https://bugs.openjdk.org/browse/JDK-8346281) runs fine now when the app runs on a given screen and the user changes its resolution. 
> 
> There is a follow-up issue after this PR, that might require a more complex fix, for the case where the user changes the resolution of a different screen that is placed before the one that has the application (as location coordinates of the latter depend on the former), because there is no `WM_DPICHANGED` event in this case.

attached an updated SCCE to the ticket.  the initial scale value seems to be incorrect in this PR.

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PR Comment: https://git.openjdk.org/jfx/pull/1668#issuecomment-2560364978