Thanks for your swift and elaborate reply. I dug a little deeper based on your questions. The problem only seems to be occurring when scrolling with a touchpad.
System: HP Elitebook 8570w, NVIDIA Quadro K1000M graphics card.
OS: Windows 10 Pro x64, Version 1709
SumatraPDF version: 3.1.2 64-bit (latest)
PDF: any PDF I tried showed same behaviour
I do not have any SDKs/toolboxes available for advanced profiling, but Windows has a built-in profiler nowadays. I have no strict evidence that the GPU activity is from SumatraPDF, but the GPU usage and scrolling are clearly correlated, as the attached image below shows. Actually, the CPU usage comes from SumatraPDF, and the GPU usage seen in the graph is caused by an instance of csrss.exe, so indeed this likely has to do with the Windows API.
I performed the following test:
- Close all other apps, make sure that nothing is running in background.
- Scroll through the PDF file until the top is reached, and stop when the top is reached.
- Wait for a few seconds, and “overscroll:” continue scrolling up, although PDF is already at the top.
See the usage graphs here: https://imgur.com/a/68VYH
Finally, I think the most important observation is that this only happens when I use multitouch gestures on my touchpad for scrolling. I tried the same thing as described above when scrolling with a mouse or by pressing the middle mouse button and dragging, but in both cases CPU/GPU went down to zero when the top was reached. It seems to be something that only happens with the touchpad.