RFR: JDK-8312518 : [macos13] setFullScreenWindow() shows black screen on macOS 13 & above

[Harshitha Onkar]

On Wed, 10 Jan 2024 23:45:57 GMT, Sergey Bylokhov <serb at openjdk.org> wrote:

>> A black screen is seen on newer versions of macOS (13.3 & above) when a window is set to full-screen using `setFullScreenWindow()`. The root cause was narrowed down to the shield level of the full-screen window vs the shield level of the captured display.
>> 
>> Following solutions were explored -
>> 
>> 1. Setting `kCGMaximumWindowLevelKey` as the shield level for the full screen window. But setting the fullscreen window to maximum available window level might cause z-order issues when other popup/screen savers are involved.
>> 
>>           int shieldLevel = CGWindowLevelForKey(kCGMaximumWindowLevelKey);
>>           window.preFullScreenLevel = [nsWindow level];
>>           [nsWindow setLevel: shieldLevel];
>> 
>> 2. Raise the window's level slightly (shieldLevel + 1) above the system shield window. 
>> 
>>             int shieldLevel = CGShieldingWindowLevel();
>>             window.preFullScreenLevel = [nsWindow level];
>>             [nsWindow setLevel: (shieldLevel + 1)]; 
>> 
>> 3. Keeping the shielding level as-is and bringing the window to the foreground after display is captured. The 3rd approach **(also the one Apple recommends)** ensures that the full screen window has focus as well as being visible and also maintains the correct z-order. This solution works as expected on older (< 13.3) and newer versions (13.3 & above) of macOS.
>> 
>>           if (CGDisplayCapture(aID) == kCGErrorSuccess) {
>>                 ...
>>                 ...
>>                 int shieldLevel = CGShieldingWindowLevel();
>>                 window.preFullScreenLevel = [nsWindow level];
>>                 [nsWindow setLevel: shieldLevel];
>>                 [nsWindow makeKeyAndOrderFront: nil];
>>             }
>
> How it will work now(and worked before) if the user will call toBack() on the such fullscreen window?

@mrserb 
> How it will work now(and worked before) if the user will call toBack() on the such fullscreen window?

Tested both cases 
- current fix on macOS 13.3 & above + fullScreenWindow.toBack() 
- original code on older macOS version (11.5) + fullScreenWindow.toBack() 

It works the same in both cases - the shield window becomes the topmost window and a black screen is seen.

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PR Comment: https://git.openjdk.org/jdk/pull/17358#issuecomment-1886019314