In addition to JDK-8386317, I proposed adding an API that would allow
JavaFX applications to obtain the window corner radius from the
operating system. However, Michael Strauß pointed out that this is most
likely not feasible because operating systems generally do not expose
such information.
Let's look at the problem from a practical perspective. Virtually every
application running in a non-maximized window requires a border
(typically 1 px). This is a standard UI convention. If JavaFX supports
EXTENDED windows with rounded corners, the corners of that border must
also be rendered correctly. Otherwise, the result will look visually
inconsistent.
If obtaining the corner radius from the OS is not possible, I would
suggest one of the following solutions:
1. Add an API that allows the operating system to render the window
border itself, while the JavaFX developer only specifies its
appearance (color, thickness, dash pattern, etc.).
2. Allow the JavaFX developer to specify the corner radius explicitly,
while the operating system uses that information solely for
rendering the native window shadow.
Best regards, Pavel
