Did some editing on the new Photoshop version 21.2.0 on Windows 10 version 1903 desktop, and discovered 2 problems. I would appreciate others confirming or denying.
1. With a Levels adjustment layer, if I hold the Alt key while dragging the shadows or highlights adjustment I should see a live clipping display. I don't. The screen goes white for highlights or black for shadows, but never changes as I drag the sliders. But if I "toggle" the Alt key while still holding left click on the slider, then I get an accurate clipping display. However, if I continue dragging the slider, the display does not change until I toggle the Alt key again.
But there's more: If I drag either slider, then press Alt to see a clipping display, then release Alt, then return the slider to the original position, the display continues to show the adjustment as it was when Alt was pressed. In other words, returning the slider to the original position does not remove the adjustment. Even if I turn the Levels adjustment layer off, the display continues to show the adjustment. If I delete the Levels adjustment layer, the display returns to normal. I saved an image when it was in this bogus state, and it was OK when reloaded. So the error is in the display, not in the image data itself.
2. I use the Channel Mixer to increase saturation and have a simple action to set it up. Been doing that for years. Under 21.2.0, the initial display is clearly wrong. The adjustment is way too high. But if I then add another adjustment layer (Levels, Curves, HueSat, anything) and make a minimum change, the display becomes correct for the underlying Channel Mixer adjustment. If I delete the other adjustment layer, the display remains correct for the Channel Mixer layer. But if I change the Channel Mixer layer (opacity), the display goes crazy again.
Both these issues occur with my GPU on and off, so I don't think that common culprit is at fault. At no time do I exceed memory (less than 50% usage). It appears there is a problem with Photoshop 21.2.0 creating the correct display for a stack of adjustment layers.
