Bug 505421

On Windows, Krita's Canvas Acceleration Renderer settings seem to break/interfere with Tablet Input API. Changing the renderer can cause either/both of the 2 following symptoms: 
1) Slower frame rate;
2) Broken Tablet Input. 

The problem is, I was unable to reproduce these problems reliably. I tested on 2 PCs:

PC1: Ryzen 7 7840U, LPDDR5X 7500, 64GB, 16GB assigned to VRAM, Cintiq Pro 24 Pen Display.
PC2: Ryzen 7 8845HS, DDR5 5600, 32GB, 8GB assigned to VRAM, Huion Frego S L310 Tablet.

Both are running Windows 11 24H2 with all the patches and the latest drivers installed. PC1's Windows is only for testing purposes, so it is very clean and rarely used. PC2's Windows is freshly installed with nothing else but Krita.

I was unable to trigger anything on PC1. While I can always trigger something on PC2, the combination of the settings is different every time.

The following description only applies to PC2:

1. ANGLE is noticeably slower than OpenGL. Maybe half of the frame rate. Not to the point of unusable, but certainly not very enjoyable to draw under such condition.

2. Switching between ANGLE and OpenGL can sometimes break the Tablet Input API. When it happens, there is no pressure sensitivity, sample rate is so low, a curve becomes a poly-line. Restarting Krita doesn't help. I must change the Tablet Input API settings for it to work again. It sometimes breaks under Wintab, sometimes under Window Ink, regardless of the Huion Driver's Windows Ink option. While things are broken inside Krita, everything still works as intended outside Krita.

I have tested both Krita 5.2.9 and the latest Krita Next, they are all affected. 

Same hardware, no problem under Linux at all.

A considerable amount of users from my community reported similar issues in the past. If you need more information, please tell me how to test, and I will try my best.