Grayout "Pcbnew Manual" if there is no manual present or redirect to online manual

[Thomas Pointhuber]

# Current Behaviour

1. click on "Help" -> "Pcbnew Manual" when there is no offline manual
2. get "Help file "pcbnew" could not be found."

# Expected Behaviour

gray out items which would not work or fallback with a redirect to the online reference (for example add a link in the help message)

# System informations

Application: kicad
Version: (5.0.0-rc2-dev-769-g8f6ae7040), debug build
Libraries:
    wxWidgets 3.1.1
    libcurl/7.60.0 OpenSSL/1.1.0h zlib/1.2.11 libidn2/2.0.4 libpsl/0.20.2 (+libidn2/2.0.4) nghttp2/1.31.1
Platform: Linux 4.16.9-1-ARCH x86_64, 64 bit, Little endian, wxGTK
Build Info:
    wxWidgets: 3.1.1 (wchar_t,wx containers) GTK+ 2.24
    Boost: 1.66.0
    OpenCASCADE Community Edition: 6.9.1
    Curl: 7.60.0
    Compiler: Clang 6.0.0 with C++ ABI 1002

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

[Jeff Young (jeyjey)]

Greyed out menus don't give users the opportunity to discover /why/ they're greyed out.

Adding a link to the online manual in the error dialog is an excellent idea.

[Jeff Young (jeyjey)]

We're past string-freeze so this will have to wait for 6.0.

[Nick Østergaard (nickoe)]

Before v4 we discussed how to handle this. We waited to create a solution until we settled on how the online manual was hosted.

I would like to see kicad try local, then search the web with the following URL scheme:

http://docs.kicad-pcb.org/{tag}/{lang}/{appname}.html

The {tag} should use the tag from git if it is simple, that is -- without a dash which is used for non final releases such as for 5.0.0-rc2.

The {lang} we should already have from the language selected in kicad.

And I guess the {appname} is also available as we already use this for specify the file to open.

[KiCad Janitor (kicad-janitor)]

KiCad bug tracker has moved to Gitlab. This report is now available here: https://gitlab.com/kicad/code/kicad/-/issues/2142