Commit 7c4229c0 leads to degenerate zone geometry

Description

Commit 7c4229c0 fixed the minimum zone width not respected issue, but introduced degenerate zone geometry instead. This happens whenever 2 zones of the same net overlap. This is a regression compared to both v9 and v10 before the commit.

image.pngimage.png

There are also weird fingers even within a single zone:

image.png

Steps to reproduce

  1. Create 2 overlapping zones on the same net
  2. fill zones

KiCad Version

Application: KiCad PCB Editor x86_64 on x86_64

Version: 10.0.0-rc2-483-g10592c242d, release build

Libraries:
	wxWidgets 3.2.8 
	FreeType 2.14.1
	HarfBuzz 12.3.2
	FontConfig 2.17.1
	libcurl/8.7.1 (SecureTransport) LibreSSL/3.3.6 zlib/1.2.12 nghttp2/1.68.0

Platform: macOS Version 26.3 (Build 25D125), 64 bit, Little endian, wxMac
OpenGL: ATI Technologies Inc., AMD Radeon Pro 5300M OpenGL Engine, 2.1 ATI-7.1.6

Build Info:
	Date: Mar 10 2026 01:17:18
	wxWidgets: 3.2.8 (wchar_t,wx containers)
	Boost: 1.90.0
	OCC: 7.9.3
	Curl: 8.7.1
	ngspice: 45.2
	Compiler: Clang 17.0.0 with C++ ABI 1002
	KICAD_IPC_API=ON
	KICAD_USE_PCH=OFF