OSX Display tearing

[IcemarkUK]

It's a difficult one to show, as video doesn't capture it.

Compared to Cocos2d-x v4 all large movement (transitions etc) seems to show a lot of tearing. Most noticeably in game when scrolling a full window of a TMX layer. Happens in Windowed or Fullscreen mode. I don't see any tearing on Cocos2d-x

This could be connected to my issue with full screen as my iMac is 5120x2880 but running at 2880x1620

I wondered if there is a problem with too big frame buffer, therefore doing too much work, or refresh/fps/vsync issue

[rh101]

Are you able to use any profiling tools on the Mac? Finding any code hotspots, excessive graphic related calls etc. may help.

[rh101]

I didn't notice any screen tearing while running it at 2560x1440. Is there a specific part of the app I should be looking at? I was in the map screen, moving it around.

[IcemarkUK]

It's most obvious when scrolling around the full map, but I see it on all the transitions and when moving the main view around (dragging the display window). But I do suspect it's something to do with apple retina on my iMac and that my display is 5k

If you check map_panel_detailed::Init

    if ( mr->config->debug_map ) {
        mapBuilder->setFlags(mapflags::debug_map);
        mapBuilder->setFlags(mapflags::show_all_characters);
        mapBuilder->setFlags(mapflags::show_all_critters);
    }

With debug map on you can scroll the whole map.

[IcemarkUK]

It appears to be this...

axmol/core/platform/GLViewImpl.cpp

Lines 524 to 533 in bee2d62

	NSView* contentView = [(id)getCocoaWindow() contentView];
	[contentView setWantsLayer:YES];
	CAMetalLayer* layer = [CAMetalLayer layer];
	[layer setDevice:device];
	[layer setPixelFormat:MTLPixelFormatBGRA8Unorm];
	[layer setFramebufferOnly:YES];
	[layer setDrawableSize:size];
	layer.displaySyncEnabled = _glContextAttrs.vsync;
	[contentView setLayer:layer];
	backend::DriverMTL::setCAMetalLayer(layer);

If I set layer.displaySyncEnabled = true then the problem goes away - which makes sense.

[rh101]

I'm glad you found the issue. This shouldn't require any game engine changes, since it's just a matter of setting the vsync value via GLView::setGLContextAttrs (in AppDelegate), or if done dynamically, then recreating the view if required.

[IcemarkUK]

Seems like there should be a more formal way of doing this. I've not seen anything in engine or documentation about vsync. And it also looks like a change of behaviour. I don't think its set in Cocos2d-x - so I think it must default to true as opposed to false.

[rh101]

Cocos2d-x didn't have that section of code to set the layer.displaySyncEnabled, neither did it have the vsync member in GLContextAttrs, as you can see here:

// Cocos2d-x v4 GLContextAttrs
struct GLContextAttrs
{
    int redBits;
    int greenBits;
    int blueBits;
    int alphaBits;
    int depthBits;
    int stencilBits;
    int multisamplingCount;
};

The reason it was working in Cocos2d-x was purely a fluke, given that the default value of displaySyncEnabled is true:
https://developer.apple.com/documentation/quartzcore/cametallayer/2887087-displaysyncenabled?language=objc

I wasn't aware of the vsync addition in Axmol, and never had a reason to look into it, but at least we know about it now, and can make sure it's documented. It's actually a good addition, since the game can switch it on or off at runtime, even having it as an option the user can change.

It would be as straightforward as:

auto glContextAttrs = GLView::getGLContextAttrs();
glContextAttrs.vsync = true|false;
GLView::setGLContextAttrs(glContextAttrs);

Then call GLViewImpl::createWithFullScreen or GLViewImpl::createWithRect to recreate the view.