<AWT Dev> RFR: 8267430: GraphicsDevice.setDisplayMode(REFRESH_RATE_UNKNOWN) throws AE: Unable to set display mode! [v2]

[Sergey Bylokhov]

On Mon, 7 Jun 2021 15:17:48 GMT, Phil Race <prr at openjdk.org> wrote:

>> There are two issues here, both macOS specific.
>> First the original reported one that occurs when running on a shared remote VNC type desktop on macOS.
>> Only a single supported display mode is returned and it is also the current mode.
>> A program that simply enumerates the reported modes and tries to set them, if it reaches the native layer,
>> will fail because macOS reports the same display mode it returned as valid as now being illegal.
>> It does not appear to be as simple as a user's permission level since it occurs with an admin user as well
>> so it probably is the case that macOS simply does not allow this shared desktop to be changed although
>> there's no docs I can find
>> Ordinarily we would not have tried this since we test if the requested display mode is the same as the native
>> one and skip it, but the provided test used REFRESH_RATE_UNKNOWN which is allowed as meaning match
>> any mode that satisfies W,H,BPP. But this caused it to fail the equals test so the code is enhanced to check for that
>> 
>> Second, when creating a test it was discovered that *at least* on the built-in retina display of a 16" macbook pro,
>> the system default contig is never in the list of available modes and can be discovered only by querying the *current* mode
>> before any modes are changed. This beheaviour is 100% consistent no matter if the system was just rebooted, has
>> an external monitor attached as well, or not, activates the discrete card, or not.
>> 
>> Since we've had code since at least 2013 that added the default mode I suspect this has been seen before but nowhere
>> can I find an explanation.
>> 
>> It has odd consequences like after you change the display mode, you will no longer see the default display mode reported,
>> so the list of available modes is reduced by one.
>> But for a typical use case which doesn't re-query or more typically caches the original display mode in order to restore it, it presents a bigger problem that trying to restore will always fail. 
>> 
>> So the other thing this fix does is detect when we fail to restore the initial mode and try again in a different way.
>> Only if that fails do we then throw an exception.
>
> Phil Race has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8267430: GraphicsDevice.setDisplayMode(REFRESH_RATE_UNKNOWN) throws IAE: Unable to set display mode

src/java.desktop/macosx/classes/sun/awt/CGraphicsDevice.java line 72:

> 70:     public CGraphicsDevice(final int displayID) {
> 71:         this.displayID = displayID;
> 72:         this.initialMode = getDisplayMode();

This probably should be revalidated when this device is invalidated, otherwise deleted device will restore its own old-initial mode, instead of the new-mode for the new device.

-------------

PR: https://git.openjdk.java.net/jdk/pull/4373