Throughout the codebase, the scale is defined as i32.
This makes it impossible to properly obtain or set a scale, since compositors don't use integers for this. As a result, applications using client-toolkit are rendered blurry.

For example, on my current setup:

$ swaymsg -t get_outputs
Output eDP-1 'Sharp Corporation 0x148B 0x00000000'
  Current mode: 3840x2160 @ 59.997002 Hz
  Scale factor: 2.500000...

Output DP-2 'Ancor Communications Inc ROG PG348Q #ASMuhJCcVsHd' (focused)
  Current mode: 3440x1440 @ 59.973000 Hz
  Scale factor: 1.500000
...

I took a quick look at sway's codebase, and it seems to use double or float for scaling factors (although defined simply at 1.5 in the config).