Subtle display artifacts when mouse interacts with semi-transparent or opaque UI elements?

[70maililei]

Thanks a lot for this great job which solved the HiDPI display problem of external display Dell P2418D (2560*1400, 24 inch) collected to my M1 MBA. It can display with 1080P HiDPI solution to provide very nice text display effect.

I've found a little problem that when using BetterDummy to realize HiDPI solution, the mouse pointer is surrounded by a square shadow frame if it is slip over some semitransparent UI component, such as background of the Safari 15 start page.

My OS version is 10.15.2. M1 MBA and the display is collected with USB Type-C to DP cable. I had tried Type-C to HDMI cable but the problem described above still exist.

See the video attached to describe the problem.

Filmage.2021-11-22_153057.mp4

[waydabber]

Hi, yes, this is effect is present with the macOS CGVirtualDisplay in general on the M1 (I didn't try Intel). You can see this effect without BetterDummy as well if you use Sidecar, AirPlay and possibly a DisplayLink adapter. The effect is indeed subtle. Transparent menus are affected as well.

This cannot be fixed on BetterDummy's side as this is a macOS issue.

[waydabber]

Btw I think in case of these shader based effects the virtual display renderer works a bit differently, probably only a specific area of the display is updated by a change - macOS does things like this habitually for energy efficiency, you can use Quartz Debugger to highlight areas that change on screen and are considered dirty and in need of redrawing. This is probably because CGVirtualDisplay was mainly designed for compressed desktop streaming and limiting changes to specific areas helps the compression algorithm. But this is just an educated guess.

[70maililei]

Thanks a lot for your interpretation!