flashing problem with samples on Metal in macOS Ventura Topic is solved

[jwwalker]

BTW this is an extreme long shot but it is worth a try: Does the problem go away if you set CMake variable OGRE_RESTRICT_ALIASING to OFF and change # define DECL_MALLOC __attribute__( ( malloc ) ) from OgrePlatform.h to # define DECL_MALLOC ?

It wouldn't be the first time that a compiler became better at optimizing, and turns out it revealed a bug in our code (it's basically a very aggressive optimization).

I doubt this is the case because this shouldn't affect debug builds, but it's not entirely impossible.

No change.

[jwwalker]

Mmm... I wonder if this is an @autorelease pool issue. i.e. The ptrs getting released too early.

I tried commenting out every instance of @autoreleasepool and saw no difference in Tutorial00.

[dark_sylinc]

Great! After commenting them out, add one here:

Code: Select all

@autoreleasepool
{
    while( !bQuit )
    {
        WindowEventUtilities::messagePump();
        bQuit |= myWindowEventListener.getQuit();
        if( !bQuit )
            bQuit |= !root->renderOneFrame();
    }
}

You will have to rename the file Tutorial00_Basic.cpp to Tutorial00_Basic.mm though

[jwwalker]

Still no change with the new @autoreleasepool.

[jwwalker]

I think I've solved it. Consider this code from OgreMetalWindow.mm:

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    void MetalWindow::swapBuffers()
    {
        if( !mDevice->mFrameAborted )
        {
            // Schedule a present once rendering to the framebuffer is complete
            const CFTimeInterval presentationTime = mMetalView.presentationTime;

            if( mMetalLayer.presentsWithTransaction )
            {
                id<MTLCommandBuffer> commandBuffer = mDevice->mCurrentCommandBuffer;
                mDevice->commitAndNextCommandBuffer();
                [commandBuffer waitUntilScheduled];
                [mCurrentDrawable present];
            }
            else if( presentationTime < 0 )
            {
                [mDevice->mCurrentCommandBuffer presentDrawable:mCurrentDrawable];
            }
            else
            {
                [mDevice->mCurrentCommandBuffer presentDrawable:mCurrentDrawable
                                                         atTime:presentationTime];
            }
        }

        if( !mManualRelease )
            mCurrentDrawable = 0;
    }

Normally, presentsWithTransaction is false, and the view's presentationTime has not been set, so it has its initial value of 0. Therefore the last else clause runs. I'm guessing that what changed in Ventura is the behavior of -[MtlCommandBuffer presentDrawable:atTime:] when it is passed a time that is 0, or maybe anything less than the current time. If we change the last else if to

Code: Select all

else if( presentationTime <= 0.0 )

then the flicker goes away.

[dark_sylinc]

You're telling me that it flickers when presentationTime == 0 (and exactly 0)???

That's a massive bug on their end.

In the meantime we can workaround it.

Good detective work there! Thanks!

[dark_sylinc]

Oh I confused presentDrawable atTime with afterMinimumDuration.

Looking at documentation, atTime is a mach absolute value. Passing a value of 0 is definitely wrong.

Update: Passing a value of 0 should be right. What is wrong is the default value shouldn't be 0, but -1

Update 2: OgreMetalView.mm sets presentationTime to -1. Why is it not -1 in your case?
Update 3: TutorialViewController.mm is probably buggy as well.

[jwwalker]

Update 2: OgreMetalView.mm sets presentationTime to -1. Why is it not -1 in your case?

I don't see anything in OgreMetalView.mm that sets presentationTime to anything.

[dark_sylinc]

OH, you are right. It's only set in iOS, but not macOS.

This is a bug in our end.

[dark_sylinc]

Fixed.

I also double checked TutorialViewController.mm, that one is right after all, because it is relative to CADisplayLink::timestamp

Thanks for looking into this problem so thoroughly.

[jwwalker]

You're welcome, and thanks for your attention to it.