[pangomm/kjellahl/meson-build-1-4] meson: Relax Visual Studio check to 2013

[Chun-wei Fan <fanchunwei src gnome org>]

commit fa6e21ea0588e9c13cb23885cf4e86e0c41c290c
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Mon Nov 4 17:52:03 2019 +0800

    meson: Relax Visual Studio check to 2013
    
    We are able to build the C++-11 version of pangomm on Visual Studio 2013
    or later, so check for that.
    
    However, since the C++-11 support in Visual Studio is made complete in
    VS 2015, display a warning message to configure the build without
    warnings being fatal, as 2013 builds will spew compiler warnings.
    
    Also, for the C++-11 versions of glibmm, cairomm and sigc++, we don't
    distinguish between whether they are built by Visual Studio 2015, 2017
    nor 2019, so we assume that they will all link to the same .lib's for
    glibmm, cairomm and sigc++, since they should all be compatible in this
    case.  In this case, Meson will warn about C++11 is not supported, but
    it is safe to ignore this warning.

 meson.build | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)
---
diff --git a/meson.build b/meson.build
index 694356a..6b7c964 100644
--- a/meson.build
+++ b/meson.build
@@ -96,8 +96,8 @@ glibmm_req_minor_ver = '4'
 cairomm_req_minor_ver = '0'
 
 if is_msvc
-  # We must have Visual Studio 2017 15.7 or later...
-  assert(cpp_compiler.version().split('.')[0].to_int() >= 19 and 
cpp_compiler.version().split('.')[1].to_int() >= 15, 'Visual Studio 2017 15.7 or later is required')
+  # We must have Visual Studio 2013 or later...
+  assert(cpp_compiler.version().split('.')[0].to_int() >= 18, 'Visual Studio 2013 or later is required')
 
   assert(cpp_compiler.has_header('sigc++-2.0/sigc++/sigc++.h') and 
cpp_compiler.has_header('sigc++-2.0/include/sigc++config.h'),
          'sigc++-2.x headers are required')
@@ -107,12 +107,17 @@ if is_msvc
          'cairomm-1.@0@ headers are required'.format(cairomm_req_minor_ver))
   message('Ensure your INCLUDE and LIB contain the paths that lead to the appropriate headers and .lib\'s 
for glibmm-2.@0@, cairomm-1.@1@ and libsigc++-2.x'.format(glibmm_req_minor_ver, cairomm_req_minor_ver))
 
-  # Visual Studio 2019 can consume libraries built with 2017, so check for
-  # 2017-built libraries as well if 2019-built libraries cannot be found
-  msvc_check_range = [15]
-  msvc_minor = cpp_compiler.version().split('.')[1].to_int()
-  if msvc_minor >= 20
-    msvc_check_range = [16, 15]
+  # We need to look for appropriate versions of Visual
+  # Studio since those built by NMake and the former
+  # Visual Studio projects are versioned by the VS versions
+  if cpp_compiler.version().split('.')[0].to_int() == 18
+    msvc_check_range = [12] # Visual Studio 2013
+    warning('Visual Studio 2013 must configure without -Dwarnings=fatal, which is the default')
+  elif cpp_compiler.version().split('.')[0].to_int() == 19
+    # Visual Studio 2019 can consume libraries built with 2017 and 2015
+    # and Visual Studio 2017 can consume libraries built with 2015
+    msvc_check_range = [14] # Visual Studio 2015, 2017, 2019
+    message('It is safe to ignore warnings from Meson that MSVC does not support C++11')
   endif
 
   debugsuffix = ''