[Footprint editor] Rectangle, zone, polygon tool snap to grid is messed up
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# Description
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For some reason, the snapping in the footprint editor as of 10.0.0 is *very* hard to control unless holding shift. This is just a footprint with a single rectangle in it, set to a grid of 1 mm, first showing correct behaviour with shift held down, then showing the glitched behaviour:
{width=715 height=600}
Notice how the corner is off-grid at the end.
(see comments for further details; it turns out this affects point editors for zones and polygons too.)
# Steps to reproduce
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1. Draw a rectangle in the footprint editor.
2. Grab one corner and try to move it.
# KiCad Version
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```
Application: KiCad Footprint Editor x64 on x64
Version: 10.0.0, release build
Libraries:
wxWidgets 3.3.2
FreeType 2.13.3
HarfBuzz 12.3.0
FontConfig 2.17.1
Platform: Windows 10 (build 19045), 64-bit edition, 64 bit, Little endian, wxMSW
OpenGL: Intel, Intel(R) UHD Graphics, 4.6.0 - Build 31.0.101.2130
wxWidgets: 3.3.2 (wchar_t,STL containers)
Boost: 1.90.0
OCC: 7.9.2
Curl: 8.18.0
ngspice: 45.2
Compiler: Visual C++ 1944 without C++ ABI
KICAD_IPC_API=ON
KICAD_USE_PCH=OFF
Locale:
Lang: en_US
Enc: UTF-8
Num: 1,234.5
Encoded кΩ丈: D0BACEA9E4B888 (sys), D0BACEA9E4B888 (utf8)
```
issue