RFR: 8316419: [macos] Setting X/Y makes Stage maximization not work before show

[Martin Fox]

On Thu, 12 Oct 2023 05:52:04 GMT, Martin Fox <duke at openjdk.org> wrote:

> When a window is visible the maximized, iconified, and fullscreen properties are two-way streets; changes made in Java are sent on to the platform window and changes in the platform window are sent back into Java.
> 
> When a window is hidden these properties (and others, like location and sizing information) are not sent on to the platform window until the window is made visible. In other words, the properties don't reflect the actual state of the window but the intended state after it's shown.
> 
> There's a period when the window is transitioning from hidden to shown where the core Stage code is using the stored properties to configure the platform window and the platform window is simultaneously calling back in to update the properties. This was causing the intended state to be wiped out before it could be sent on to the platform window.
> 
> The problem is specific to Mac because on that platform any change to the size or location of a window can cause it to enter or leave the maximized (zoomed) state. So just setting the location can cause the maximized flag to be altered.
> 
> The proposed solution is to copy the intended state bits to Stage local variables to be used later in the configuration.

If the iconified, maximized, and fullscreen flags are set on a hidden window they aren't sent on to the platform until the window is shown. There are two stages:

a) before the window becomes visible the size and position is sent

b) after the window becomes visible the iconified, maximized, and fullscreen flags are sent

In the original bug the maximized and iconified properties were being altered by the platform code at the end of stage (a).

In this test case the maximized property is being set by user code between stages (a) and (b). That's when the setOnShown() action is executing.

Fun fact: on Mac the OS will report that an undecorated window is maximized (zoomed) even when it very definitely is not.

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PR Comment: https://git.openjdk.org/jfx/pull/1258#issuecomment-1769080033