[gtk/wip/fanc999/gtk-3-24-meson-msvc: 424/434] meson: Only use fallbacks for PangoFT2 and FreeType when needed

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

commit 51a9f7624e7bb5d0905477d07261a83a9bf5d61b
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Wed Mar 13 12:37:40 2019 +0800

    meson: Only use fallbacks for PangoFT2 and FreeType when needed
    
    PangoFT2 is optional on Windows, so we only really need the fallback if
    when it is required.
    
    Along with that, since FreeType does not typically ship with pkg-config
    files in its CMake builds, check for the needed headers, .lib and
    function and then use the fallback when they could not be found and
    PangoFT2 is used.

 meson.build | 29 +++++++++++++++++++++++++----
 1 file changed, 25 insertions(+), 4 deletions(-)
---
diff --git a/meson.build b/meson.build
index 1b49be2c0b..7077d3e58d 100644
--- a/meson.build
+++ b/meson.build
@@ -343,15 +343,36 @@ pango_dep      = dependency('pango', version: pango_req,
 
 # Require PangoFT2 if on X11 or wayland
 require_pangoft2 = wayland_enabled or x11_enabled
-pangoft_dep    = dependency('pangoft2', required: require_pangoft2,
-                            fallback : ['pango', 'libpangoft2_dep'])
+if require_pangoft2
+  pangoft_dep    = dependency('pangoft2', fallback : ['pango', 'libpangoft2_dep'])
+else
+  pangoft_dep    = dependency('pangoft2', required: false)
+endif
 
 if pangoft_dep.found()
   # Need at least 2.7.1 for FT_Get_Var_Design_Coordinates()
   # We get the dependency itself from pango, but pango doesn't care
   # about ft2 version, so an extra check is needed.
-  ft2_dep      = dependency('freetype2', version: '>= 2.7.1', required: require_pangoft2,
-                            fallback : ['freetype2', 'freetype_dep'])
+
+  # Update once Meson can have deps declared in a declarative manner
+  ft2_dep      = dependency('freetype2', version: '>= 2.7.1', required: false)
+
+  if not ft2_dep.found() and cc.get_id() == 'msvc'
+    if cc.has_header('ft2build.h') and cc.has_header('freetype/ftmm.h')
+      ft_lib = cc.find_library('freetype', required: false)
+      if ft_lib.found()
+        if cc.has_function('FT_Get_Var_Design_Coordinates', dependencies: ft_lib,
+                           prefix: '''#include <ft2build.h>
+                                      #include FT_MULTIPLE_MASTERS_H''')
+          ft2_dep = ft_lib
+        endif
+      endif
+    endif
+  endif
+
+  if not ft2_dep.found()
+    ft2_dep      = dependency('freetype2', version: '>= 2.7.1', fallback : ['freetype2', 'freetype_dep'])
+  endif
 endif
 
 if win32_enabled