I tryed the latest Krita 3.0 Beta with a heavy file (precisions in "additional informations") and I noticed 2 problems when I use a brush if the "Instant preview" is active:

1. Sometimes, the lines I'm drawing need time to appear (like if Krita slowed down strongly)

2. If the "set horizontal mirror mode" (and maybe the vertical one too) is activated, when I draw, for example, in the right part of my drawing, the mirrored left part won't appear until I stop drawing if we are in a zoom below 100%.

I checked: all of these problems are fixed if I deactivate the "Instant preview mode", but then, doing other things like "transform or move layers or selections" are a lot slower to do and it would be really a lot better in my opinion if we could do all of these actions (draw with brushes & transform or move) without having to activate and deactivate an option each time, as we could do on Krita 2.9.11.

Reproducible: Always

Steps to Reproduce:
1. Load a new document in high resolution
2. "Set horizontal mirror mode"
3. Check that "Instant preview Mode" in "View" is activated
4. Draw



File used for this:

    http://akelun.deviantart.com/art/Mizuko-Turn-around-v5-601638976
    151 layers
    Resolution: 4160 * 2340 px
    RGB 8-bit
    OpenGL activated
    High Quality Filtering scaling mode
    Set horizontal mirror mode activated to test and compare

Computer used to compare:

    Windows 8.1
    Motherboard: MSI Z170A Gaming 3 ATX
    Intel Core i7 6700k 4 GH
    GeForce GTX 980 Ti 6 Go
    16 Go RAM (2*8 Go)
    250 Go SSD hard disk (OS) + 1 To hard disk (File)

Other:

    Wacom Cintiq 12 WX