[Lazarus] Modal Window Crashes on Mac OS X 10.15 Beta (Catalina)

[Dmitry Boyarintsev]

On Tue, Jun 11, 2019 at 10:06 AM David Jenkins via lazarus <
lazarus at lists.lazarus-ide.org> wrote:

> I looked at the assembly for NSApplication.run, there are a lot of things
> being called and set before the call to nextEventMatching...   The
> .isRunning variable being one of them - which is read only and can't be
> set.  It can be overridden (and is one of the suggested overrides) but
> unfortunately there are times, in other parts of the code, that they look
> directly at the ._running variable where the value of .isRunning is stored
> instead of calling .isRunning (look at NSApplication._setMainWindow).
> Which sets up a mismatch between what an overridden .isRunning method would
> return and what ._running is set to.
>

Let's back-up a little bit.

Can we actually try to set the value for the instance variable?
1) it's absolutely legal in Objective-C terms (object_getInstanceVariable,
object_setInstanceVariable).
2) its' absolutely legal in KVC term. (I can presume that KVC is pretty
much based on top of objc-run time. And this is how the entire Swift<->ObjC
binding works)

Can anyone try and modify TCocoaApplication.run to look like this. (If
you're using trunk, you'll need to have {$define COCOALOOPOVERRIDE} defines
in cocoadefines.inc}

procedure TCocoaApplication.run;
begin
  self.setValue_forKey(NSNumber.numberWithBool(true),NSSTR('_running')); //
setting instance variable through KVC
  isrun:=true;
  aloop();
end;
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