Indicates whether focus can be obtained.
You can also set the value.
If set to false, you will not be able to get focus, that is, the window will not be active.
As a side effect, you will not be able to grab the title bar to move the window, resize the window, or press the "x" button to close the window.
You can use the Window.trapKey property if you want to get keyboard input.
This is usually used to implement a window that appears in the foreground, such as a pop-up menu, but does not get its own focus.
In the current version, the settings for this property may be lost when the window goes to full screen or returns from full screen.
Always true on Android.