Blurring and deformation of fonts, icons and textures with fractional scaling
Affected version
- Fedora 32
- mutter 3.36.0
- wayland
Bug summary
- Intel UHD 620 / i915
- 3840x2160 resolution
- 150% scale with scale-monitor-framebuffer enabled
Blurring and deformation of fonts, icons and textures when using non-integer (global fractional) scaling in mutter.
Steps to reproduce
- enable scale-monitor-framebuffer
- set scaling factor to non-integer value in display settings
What happened
In order to remove artifacts, mutter applies a linear interpolation filter to downscaled textures when using fractional scaling. This leads to blurring and deformation of fonts, icons and textures if they are located in certain positions. This happens because the pixels of the original texture do not fit the pixel grid of the new downscaled size.
What did you expect to happen
Sharp and undeformed fonts, icons and textures with fractional scaling. Either by using native scaling or by applying a better interpolation algorithm on downscaled textures.
Relevant screenshots / examples
Description: the character N
is deformed, because its width of the right vertical stroke is smaller than the left, also everything is blurred
Description: artifacts in the form of black lines in the window border, depends on the position of the window
Description: the middle one of the three strokes in the menu icon is blurred
Description: outer black border around the inner blue border of the text entry is deformed: lower and left side are thinner and blurred