I have a bare-bones Metal app setup where I attach a CAMetalLayer to a window that inherits from a NSWindow with a custom delegate. Everything else is vanilla. I'm also using metal-cpp and metal shader converter.
I'm running into a issue where the application runs fine in the beginning, but once I resize the window, it starts hitching. It turns out that [CAMetalLayer nextDrawable:] frequently (but not always) takes around a full second (plus or minus a few milliseconds) to return once drawableSize has been updated.
I've tried setting allowsNextDrawableTimeout to false which doesn't work; it returns a valid drawable after a second instead of nil. Setting displaySyncEnabled to false reduces the likelihood of this happening to around 50% from 90%+ but does not eliminate it. Setting maximumDrawableCount to 2 or 3 does not seem to make a difference.
By dumping the resource IDs of the returned textures I've noticed something interesting: Before resizing, the layer seems to shuffle between 2 textures or at least 2 resource IDs, but after resizing it starts to create new textures for each returned drawable. Occasionally it seems to reuse a previous resource ID, but it does not seem to have anything to do with whether the method returns quickly or not.
Why does this happen, and how can I fix it? Should I create a new CAMetalLayer when resizing the window instead of updating drawableSize?
Hello,
We recommend using CAMetalDisplayLink shown in Achieving smooth frame rates with Metal’s display link.
