Soldermask generating slow in some cases since 5.1.7

Somewhere after 5.1.6 release (pre-5.1.7 testing builds), a code change caused slow generating Soldermask if Global min.width not set to 0.

ING401_B_backup.zip

Description

Plotting soldermask can take several minutes. Plotting should take normal time (several seconds). It used to work normally in 5.1.6 It works in normal time if global Soldermask min.width is set to 0

Steps to reproduce

1.Open attached PCB (project uploaded by forum user https://forum.kicad.info/t/f-mask-plot-crashing-pcbnew/25841/13 ) 2.Go to File > Plot > select F.Mask layer and click Plot 3.Watch PCBNew goes stuck for several minutes, with "not respoding" Plot window title 4.Change global mask min.width to 0 and re-try to see speed difference

KiCad Version

Application: Pcbnew
Version: (5.1.8-9-g4497a754fb)-1, release build
Libraries:
    wxWidgets 3.0.5
    libcurl/7.71.0 OpenSSL/1.1.1g (Schannel) zlib/1.2.11 brotli/1.0.7 libidn2/2.3.0 libpsl/0.21.0 (+libidn2/2.3.0) libssh2/1.9.0 nghttp2/1.41.0
Platform: Windows 8 (build 9200), 64-bit edition, 64 bit, Little endian, wxMSW
Build Info:
    wxWidgets: 3.0.5 (wchar_t,wx containers,compatible with 2.8)
    Boost: 1.73.0
    OpenCASCADE Community Edition: 6.9.1
    Curl: 7.71.0
    Compiler: GCC 10.2.0 with C++ ABI 1014

Build settings:
    USE_WX_GRAPHICS_CONTEXT=OFF
    USE_WX_OVERLAY=OFF
    KICAD_SCRIPTING=ON
    KICAD_SCRIPTING_MODULES=ON
    KICAD_SCRIPTING_PYTHON3=OFF
    KICAD_SCRIPTING_WXPYTHON=ON
    KICAD_SCRIPTING_WXPYTHON_PHOENIX=OFF
    KICAD_SCRIPTING_ACTION_MENU=ON
    BUILD_GITHUB_PLUGIN=ON
    KICAD_USE_OCE=ON
    KICAD_USE_OCC=OFF
    KICAD_SPICE=ON