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Editing pad properties introduces rounding errors when units are set to mils.

Description

While editing pad properties in the PCB Editor, I noticed rounding errors appearing. After a bit more testing, these rounding errors apparently only appear when the units are set to "mils".

Here is a screenshot of Meld Merge that compares two versions of the PCB: image

Steps to reproduce

  1. Make a copy a PCB file.
  2. Start Meld Merge (or other diff program). The copy is of course the same as the original).
  3. Open the PCB in KiCad, Make sure units to Mils in the PCB Editor.
  4. Select a single pad and press e to edit it.
  5. Change one of the pad properties, SMT/THT, "Copper layers", pad nr, etc, It does not matter which parameter, and click on [OK].
  6. Save the PCB.
  7. My diff program (Meld) detects the file change and asks to reload it.
  8. After reloading it, rounding errors have appeared in the pad for which the properties have changed.

KiCad Version

Application: KiCad PCB Editor

Version: 6.0.6-3a73a75311~116~ubuntu20.04.1, release build

Libraries:
	wxWidgets 3.0.4

Platform: Linux 5.15.0-33-generic x86_64, 64 bit, Little endian, wxGTK, xfce, x11

	wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8) GTK+ 3.24
	Boost: 1.71.0
	OCC: 7.5.2
	Curl: 7.83.1
	ngspice: 36
	Compiler: GCC 9.4.0 with C++ ABI 1013

Build settings:
	KICAD_USE_OCC=ON
	KICAD_SPICE=ON