On Tue, 9 Jan 2024 21:45:33 GMT, Marius Hanl <mh...@openjdk.org> wrote:
> This PR fixes the dialog freeze problem once and for all. > > This one is a bit tricky to understand, here is how it works: > This bug happens on every platform, although the implementation of nested > event loops differs on every platform. > E.g. on Linux we use `gtk_main` and `gtk_main_quit`, on Windows and Mac we > have an own implementation of a nested event loop (while loop), controlled by > a boolean flag. > > Funny enough, the reason why this bug happens is always the same: Timing. > > 1. When we hide a dialog, `_leaveNestedEventLoop` is called. > 2. This will call native code to get out of the nested event loop, e.g. on > Windows we try to break out of the while loop with a boolean flag, on Linux > we call `gtk_main_quit`. > 3. Now, if we immediately open a new dialog, we enter a new nested event loop > via `_enterNestedEventLoop`, as a consequence we do not break out of the > while loop on Windows (the flag is set back again, the while loop is still > running), and we do not return from `gtk_main` on Linux. > 4. And this will result in the Java code never returning and calling > `notifyLeftNestedEventLoop`, which we need to recover the UI. > > So it is actually not trivial to fix this problem, and we can not really do > anything on the Java side. We may can try to wait until one more frame has > run so that things will hopefully be right, but that sounds rather hacky. > > I therefore analyzed, if we even need to return from `_enterNestedEventLoop`. > Turns out, we don't need to. > There is a return value which we actually do not use (it does not have any > meaning to us, other that it is used inside an assert statement). > ~Without the need of a return value, we also do not need to care when > `_enterNestedEventLoop` is returning - instead we cleanup and call > `notifyLeftNestedEventLoop` in `_leaveNestedEventLoop`, after the native code > was called.~ > See below for more information. To recover the UI (and in general nested > nested event loops ;) we need to set a flag for the `InvokeLaterDispatcher`. > > Lets see if this is the right approach (for all platforms). > Testing appreciated. > # > - [x] Tested on Windows > - [x] Tested on Linux > - [x] Tested on Mac > - [ ] Tested on iOS (although the nested event loop code is the same as for > Mac) (I would appreciate if someone can do this as I have no access to an iOS > device) > - [x] Adjust copyright > - [x] Write Systemtest > - [x] Document the new behaviour - in general, there should be more > information what to expect This pull request has been closed without being integrated. ------------- PR: https://git.openjdk.org/jfx/pull/1324
