pcbnew: overlapping vias in high contrast

[Fabien Corona]

With the high contrast mode, if two microvias / blind vias are overlapping, the displayed result may be incorrect.
example : I set a microvia from layer 2 to 3 and another from 4 to 5.
The draw order of these two vias seems constant whatever the active layer is.
Therefore if the first microvia has the highest priority, then I see a darkened via when looking at layer 4 or 5, but I should be seeing the second via.

Maybe the draw priority for vias should depend on the active layer.
for information, the layer affected are : LAYER_VIA_MICROVIA, LAYER_VIA_BBLIND and LAYER_VIAS_HOLES

See video.

Application: Pcbnew
Version: 5.99.0-unknown-f8aea24~100~ubuntu18.04.1, release build
Libraries:
    wxWidgets 3.0.4
    libcurl/7.58.0 OpenSSL/1.1.1 zlib/1.2.11 libidn2/2.0.4 libpsl/0.19.1 (+libidn2/2.0.4) nghttp2/1.30.0 librtmp/2.3
Platform: Linux 4.15.0-54-generic x86_64, 64 bit, Little endian, wxGTK
Build Info:
    Build date: Nov 16 2019 00:34:10
    wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8) GTK+ 3.22
    Boost: 1.65.1
    OpenCASCADE Community Edition: 6.9.1
    Curl: 7.58.0
    Compiler: GCC 7.4.0 with C++ ABI 1011

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

[Michael Kavanagh (michaelkavanagh)]

@drinausaur, for your information - we have switched from Launchpad to GitLab. You can follow your bug report here: https://gitlab.com/kicad/code/kicad/issues/2593

[KiCad Janitor (kicad-janitor)]

KiCad bug tracker has moved to Gitlab. This report is now available here: https://gitlab.com/kicad/code/kicad/-/issues/2593