Mouse speed changes when using fractional scaling

[thekk1]

Distribution

Mint 22.3

Package version

Cinnamon 6.6.7

Graphics hardware in use

Radeon 780m (R7 7840U)

Frequency

Always

Bug description

Description:
When fractional scaling is enabled in Cinnamon, the perceived mouse speed changes depending on the selected scaling factor.

Observed behavior:

• Increasing the scaling factor (e.g. 100% → 200%) makes the mouse pointer feel slower
• Decreasing the scaling factor makes the mouse pointer feel faster
• The effect is clearly noticeable and impacts usability

Steps to reproduce

1. Open Display settings
2. Enable fractional scaling
3. Set scaling to e.g. 125% ,150% or even 200%
4. Move the mouse pointer across the screen

Expected behavior

Mouse movement speed should remain consistent and independent of display scaling.

Additional information

• When fractional scaling is disabled and integer scaling (e.g. 200%) is used, the issue does not occur

• This suggests the problem is specific to fractional scaling implementation

• Display server: X11

Notes / Hypothesis:
It appears that pointer movement is not properly normalized against the scaled coordinate space when fractional scaling is active, causing a mismatch between physical mouse movement and on-screen cursor movement.