[pango/cairo-detection-improvements: 2/2] build: Only use fallback for Cairo dep when necessary

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

commit 77e77bcf8897a58cd29a44ce1ce85e99ac28635b
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Fri Jul 19 18:23:21 2019 +0800

    build: Only use fallback for Cairo dep when necessary
    
    Only use the fallback when we are sure that we can't find the Cairo
    headers and libraries, where applicable, and ensure that it is used, as
    it is really a hard dependency.

 meson.build | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)
---
diff --git a/meson.build b/meson.build
index 13d9bbff..519251f2 100644
--- a/meson.build
+++ b/meson.build
@@ -343,8 +343,7 @@ if host_system == 'darwin'
 endif
 
 cairo_found_type = ''
-cairo_dep = dependency('cairo', version: cairo_req_version, required: false,
-                       fallback: ['cairo', 'libcairo_dep'])
+cairo_dep = dependency('cairo', version: cairo_req_version, required: false)
 
 if cairo_dep.found()
   cairo_found_type = cairo_dep.type_name()
@@ -355,6 +354,14 @@ else
   endif
 endif
 
+# Remove once Meson gains capability to declare dependencies
+# in a declarative way
+if not cairo_dep.found()
+  cairo_dep = dependency('cairo', version: cairo_req_version,
+                         fallback: ['cairo', 'libcairo_dep'])
+  cairo_found_type = cairo_dep.type_name()
+endif
+
 pango_font_backends = []
 pango_cairo_backends = []