But at the moment when it lags the system switches from hardware cursor to software cursor (CGCursorIsDrawnInFramebuffer() goes from 0 to 1) so maybe that transition is stalled somehow on Macbook Neo.
With the disclaimer that I have zero knowledge of the MacBook Neo hardware, but I do know a bit about GPUs in general (including having written some GPU-accelerated drivers for Windows and the associated cursor-handling code), I'm going to make a wild guess: this lag is caused by waiting for the GPU command queue to flush.
As a bit of background information: the GPU is fed commands from a queue that the CPU writes to. These commands perform the drawing operations that the GPU is designed to accelerate. A hardware cursor is basically a small bitmap that can be positioned anywhere on the screen and moved around by simply updating position registers (which is normally done per mouse interrupt); the hardware draws it automatically. A software cursor is manually drawn by the graphics stack, which saves what was under it, draws the cursor, and then whenever it needs to be moved, writes the original data back, saves the data at the new position, and then draws the cursor there.
Flushing the command queue is necessary when switching to a software cursor, or otherwise doing software writes to the framebuffer, because you need to wait for the GPU to finish drawing what it has queued, or it may end up drawing over what software wants to draw, including the cursor. Or worse, the command is a blit (e.g. scrolling a window) and you end up with remnants of the cursor at its previous position.
userbinator
Before reading the background info, I was going to recommend a much simpler fix, but they actually already mention it in there: "Also the mouse cursor size can be changed."
This was going to be my suggestion because it also fixed a similar CPU/GPU related issue many years ago: Apple's own TV.app would have minuscule color handling differences whenever subtitles would show during a movie. This was driving me nuts while showing a moody black & white film for a movie night - every time a subtitle would pop up, the entire scene's black levels would shift slightly (and it wasn't any kind of adaptive/localized brightness or anything like that, it was the actual rendering).
Some online sleuthing revealed it was GPU related (pure GPU video decoding vs. the CPU overlaying subtitles on the screen), and that bumping up the cursor size (even the tiniest amount) in mouse settings would fix it. It worked.
It's barely noticeable, but I actually prefer the slightly bigger mouse cursor now anyway, so it's part of my standard macOS setup.
exogen
I’m not sure what the bug is, but this is a terrible fix. What this is doing is forcing the WindowServer to composite the cursor rather than treat it as a hardware overlay. I suppose the issue must be pretty bad for OP if this helps, but … ugh.
TheTon
A fix so amusing and ridiculous it gets the bug enough attention that Apple fixes it for real.
elicash
Crazy this would be the case when the MacOS cursor has been buttery smooth and only ever lags if the entire system is about to go down even on 800Mhz G4 Titanium Powerbook this was the behavior.
whywhywhywhy
This is such a nice fix but then you install it's set it up to launch on start and forget about it. 5 years later the bug has been fixed for 4 and I still have tho script record a random pixel every 10 seconds.
Never know how to know that the hacky fix is no longer needed
anotherpaul
This is a great example of how to make a minimal app bundle with Swift. Thank you!
All an App needs on MacOS seems to be a binary and a little .plist
gcr
Bonus points if you manage to record the Facebook tracking pixel.
comments (10)
With the disclaimer that I have zero knowledge of the MacBook Neo hardware, but I do know a bit about GPUs in general (including having written some GPU-accelerated drivers for Windows and the associated cursor-handling code), I'm going to make a wild guess: this lag is caused by waiting for the GPU command queue to flush.
As a bit of background information: the GPU is fed commands from a queue that the CPU writes to. These commands perform the drawing operations that the GPU is designed to accelerate. A hardware cursor is basically a small bitmap that can be positioned anywhere on the screen and moved around by simply updating position registers (which is normally done per mouse interrupt); the hardware draws it automatically. A software cursor is manually drawn by the graphics stack, which saves what was under it, draws the cursor, and then whenever it needs to be moved, writes the original data back, saves the data at the new position, and then draws the cursor there.
Flushing the command queue is necessary when switching to a software cursor, or otherwise doing software writes to the framebuffer, because you need to wait for the GPU to finish drawing what it has queued, or it may end up drawing over what software wants to draw, including the cursor. Or worse, the command is a blit (e.g. scrolling a window) and you end up with remnants of the cursor at its previous position.
userbinator
This was going to be my suggestion because it also fixed a similar CPU/GPU related issue many years ago: Apple's own TV.app would have minuscule color handling differences whenever subtitles would show during a movie. This was driving me nuts while showing a moody black & white film for a movie night - every time a subtitle would pop up, the entire scene's black levels would shift slightly (and it wasn't any kind of adaptive/localized brightness or anything like that, it was the actual rendering).
Some online sleuthing revealed it was GPU related (pure GPU video decoding vs. the CPU overlaying subtitles on the screen), and that bumping up the cursor size (even the tiniest amount) in mouse settings would fix it. It worked.
It's barely noticeable, but I actually prefer the slightly bigger mouse cursor now anyway, so it's part of my standard macOS setup.
exogen
TheTon
elicash
whywhywhywhy
anotherpaul
All an App needs on MacOS seems to be a binary and a little .plist
gcr
amelius
m132
xnx