[eog] build: Do not use options as auto

[Iñigo Martínez <inigomartinez src gnome org>]

commit daf0193de1ab25d2fd62b37103d634f214d542a6
Author: Iñigo Martínez <inigomartinez gmail com>
Date:   Wed Feb 21 19:48:56 2018 +0100

    build: Do not use options as auto
    
    There are some options that can be used to enable or disable
    options. However, if the conditions to use those components
    enabled by options are not fulfilled, they are disabled and this
    might confuse an user.
    
    Now, if the conditions of those enabled components are not fulfilled
    the build configuration will stop showing a message to the user.
    
    meson variables have been renamed from the `have_` pattern to the
    `enable_` pattern to better reflect this behaviour.
    
    The `zlib` detection behaviour has also been fixed, which will
    require both `inflate` and `crc32` to be available.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=793719

 doc/reference/meson.build |    2 +-
 meson.build               |  155 +++++++++++++++-----------------------------
 plugins/meson.build       |    2 +-
 src/meson.build           |    6 +-
 4 files changed, 58 insertions(+), 107 deletions(-)
---
diff --git a/doc/reference/meson.build b/doc/reference/meson.build
index 83f80f0..fd4b203 100644
--- a/doc/reference/meson.build
+++ b/doc/reference/meson.build
@@ -17,7 +17,7 @@ private_headers = [
   'eog-print-preview.h'
 ]
 
-if not have_exif
+if not enable_libexif
   private_headers += 'eog-exif-util.h'
 endif
 
diff --git a/meson.build b/meson.build
index e1e61b1..1c05900 100644
--- a/meson.build
+++ b/meson.build
@@ -104,135 +104,86 @@ eog_deps = [
 ]
 
 # ZLIB support (required)
-have_zlib = false
-if cc.has_header('zlib.h')
+if not cc.has_header('zlib.h') or not (cc.has_function('inflate') and cc.has_function('crc32'))
   zlib_dep = cc.find_library('z', required: false)
-  have_zlib =  zlib_dep.found() and (cc.has_function('inflate', dependencies: zlib_dep) or 
cc.has_function('crc32', dependencies: zlib_dep))
+  assert(zlib_dep.found() and cc.has_function('inflate', dependencies: zlib_dep) and 
cc.has_function('crc32', dependencies: zlib_dep),
+         'No sufficient zlib library found on your system')
 
-  if have_zlib
-    eog_deps += zlib_dep
-  endif
+  eog_deps += zlib_dep
 endif
-assert(have_zlib, 'No sufficient zlib library found on your system')
 
 # EXIF (optional)
-have_exif = false
-if get_option('libexif')
+enable_libexif = get_option('libexif')
+if enable_libexif
   libexif_dep = dependency('libexif', version: '>= 0.6.14', required: false)
-  have_exif = libexif_dep.found() and cc.has_header('libexif/exif-data.h', dependencies: libexif_dep)
+  assert(libexif_dep.found() and cc.has_header('libexif/exif-data.h', dependencies: libexif_dep),
+         'libexif support requested but library not found. Please use -Dlibexif=false')
 
-  if have_exif
-    eog_deps += libexif_dep
-    config_h.set10('HAVE_EXIF', true,
-                   description: 'EXIF Support.')
-  endif
+  eog_deps += libexif_dep
+  config_h.set10('HAVE_EXIF', true)
 endif
 
 # Little CMS (optional)
-have_lcms = false
-if get_option('cms')
-  libcms_dep = dependency('lcms2', required: false)
-  have_lcms = libcms_dep.found()
-
-  if have_lcms
-    eog_deps += libcms_dep
-    config_h.set10('HAVE_LCMS', true,
-                   description: 'Little CMS Support.')
-  endif
+enable_cms = get_option('cms')
+if enable_cms
+  eog_deps += dependency('lcms2')
+  config_h.set10('HAVE_LCMS', true)
 endif
 
 # Exempi (optional)
-have_exempi = false
-if get_option('xmp')
-  libexempi_dep = dependency('exempi-2.0', version: '>= 1.99.5', required: false)
-  have_exempi = libexempi_dep.found()
-
-  if have_exempi
-    eog_deps += libexempi_dep
-    config_h.set10('HAVE_EXEMPI', true,
-                   description: 'XMP Support.')
-  endif
+enable_xmp = get_option('xmp')
+if enable_xmp
+  eog_deps += dependency('exempi-2.0', version: '>= 1.99.5')
+  config_h.set10('HAVE_EXEMPI', true)
 endif
 
 # Jpeg (semi-optional)
 jpeg_deps = []
 
-have_jpeg = false
-have_jpeg_80 = false
-
-if get_option('libjpeg')
+enable_libjpeg = get_option('libjpeg')
+if enable_libjpeg
   libjpeg_dep = dependency('libjpeg', required: false)
-  if libjpeg_dep.found()
-    have_jpeg = cc.has_function('jpeg_destroy_decompress', dependencies: libjpeg_dep) and 
cc.has_header('jpeglib.h', dependencies: libjpeg_dep)
-
-    if have_jpeg
-      jpeg_deps += libjpeg_dep
-
-      have_progressive = cc.has_function('jpeg_simple_progression', dependencies: libjpeg_dep)
-      if not have_progressive
-        message('JPEG library does not support progressive saving.')
-      endif
-
-      message('Checking libjpeg version is 8 or greater')
-      jpeg_80_check_src = '''
-        #include <stdio.h>
-        #include <jpeglib.h>
-        #if JPEG_LIB_VERSION < 80
-        #error "wrong version"
-        #endif
-      '''
-      have_jpeg_80 = cc.compiles(jpeg_80_check_src, dependencies: libjpeg_dep)
-    else
-      error_msg = '*** JPEG loader will not be built (JPEG header file not found) ***\n'
-    endif
-  else
-    error_msg = '*** JPEG loader will not be built (JPEG library not found) ***\n'
-  endif
+  assert(cc.has_function('jpeg_destroy_decompress', dependencies: libjpeg_dep) and 
cc.has_header('jpeglib.h', dependencies: libjpeg_dep),
+         'libjpeg support requested but library not found. Please use -Dlibjpeg=false (some programs using 
GTK+ may not work properly)')
 
-  if not have_jpeg
-    error_msg += '*** You can build without it by passing -Dlibjpeg=false to\n'
-    error_msg += '*** meson but some programs using GTK+ may not work properly\n'
-    error(error_msg)
+  jpeg_deps += libjpeg_dep
+
+  if not cc.has_function('jpeg_simple_progression', dependencies: libjpeg_dep)
+    message('JPEG library does not support progressive saving.')
   endif
 
-  config_h.set10('HAVE_JPEG', true,
-                 description: 'Jpeg Support.')
+  jpeg_80_check_src = '''
+    #include <stdio.h>
+    #include <jpeglib.h>
+    #if JPEG_LIB_VERSION < 80
+    #error "wrong version"
+    #endif
+  '''
+  have_jpeg_80 = cc.compiles(jpeg_80_check_src, dependencies: libjpeg_dep, name: 'libjpeg version is 8 or 
greater')
+
+  config_h.set10('HAVE_JPEG', true)
 endif
-config_h.set('HAVE_LIBJPEG', have_jpeg,
-             description: 'libjpeg is Present.')
+config_h.set('HAVE_LIBJPEG', enable_libjpeg)
 
 # introspection support
-have_gir = false
-if get_option('introspection')
-  gir_dep = dependency('gobject-introspection-1.0', version: '>= 0.6.7', required: false)
-  have_gir = gir_dep.found()
-
-  if have_gir
-    eog_deps += gir_dep
-  endif
+enable_introspection = get_option('introspection')
+if enable_introspection
+  eog_deps += dependency('gobject-introspection-1.0', version: '>= 0.6.7')
 endif
-config_h.set('HAVE_INTROSPECTION', have_gir)
+config_h.set('HAVE_INTROSPECTION', enable_introspection)
 
 # RSVG (optional for scaling svg image)
-have_rsvg = false
-if get_option('librsvg')
-  librsvg_dep = dependency('librsvg-2.0', version: '>= 2.36.2', required: false)
-  have_rsvg = librsvg_dep.found()
-
-  if have_rsvg
-    eog_deps += librsvg_dep
-  endif
+enable_librsvg = get_option('librsvg')
+if enable_librsvg
+  eog_deps += dependency('librsvg-2.0', version: '>= 2.36.2')
 endif
-config_h.set('HAVE_RSVG', have_rsvg,
-             description: 'RSVG Support.')
+config_h.set('HAVE_RSVG', enable_librsvg)
 
 # libX11 (required for TotemScrSaver and Color Profiling)
 gdk_dep = dependency('gdk-3.0', required: false)
 
-if have_lcms or (gdk_dep.found() and gdk_dep.get_pkgconfig_variable('targets').contains('x11'))
-  libx11_dep = dependency('x11', required: false)
-  assert(libx11_dep.found(), 'X development libraries (libX11) not found')
-  eog_deps += libx11_dep
+if enable_cms or (gdk_dep.found() and gdk_dep.get_pkgconfig_variable('targets').contains('x11'))
+  eog_deps += dependency('x11')
 endif
 
 gnome = import('gnome')
@@ -246,7 +197,7 @@ top_inc = include_directories('.')
 
 subdir('data')
 
-if have_jpeg
+if enable_libjpeg
   subdir('jpegutils')
 endif
 
@@ -278,9 +229,9 @@ output = 'Configure summary:\n\n'
 output += '  Source code location .......:  ' + meson.source_root() + '\n'
 output += '  Compiler ...................:  ' + cc.get_id() + '\n'
 output += '  Extra Compiler Warnings ....:  ' + ' '.join(compiler_flags) + '\n'
-output += '  EXIF support ...............:  ' + have_exif.to_string() + '\n'
-output += '  XMP support ................:  ' + have_exempi.to_string() + '\n'
-output += '  JPEG support ...............:  ' + have_jpeg.to_string() + '\n'
-output += '  Colour management support ..:  ' + have_lcms.to_string() + '\n'
-output += '  GObject Introspection.......:  ' + have_gir.to_string() + '\n'
+output += '  EXIF support ...............:  ' + enable_libexif.to_string() + '\n'
+output += '  XMP support ................:  ' + enable_xmp.to_string() + '\n'
+output += '  JPEG support ...............:  ' + enable_libjpeg.to_string() + '\n'
+output += '  Colour management support ..:  ' + enable_cms.to_string() + '\n'
+output += '  GObject Introspection.......:  ' + enable_introspection.to_string() + '\n'
 message(output)
diff --git a/plugins/meson.build b/plugins/meson.build
index c54ca8a..bf49ba0 100644
--- a/plugins/meson.build
+++ b/plugins/meson.build
@@ -5,7 +5,7 @@ plugins = [
   'reload'
 ]
 
-if have_exif
+if enable_libexif
   plugins += 'statusbar-date'
 endif
 
diff --git a/src/meson.build b/src/meson.build
index ef28020..0c985bf 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -88,12 +88,12 @@ sources = files(
   'zoom.c'
 )
 
-if have_exif
+if enable_libexif
   headers += files('eog-exif-util.h')
   sources += files('eog-exif-util.c')
 endif
 
-if have_exif or have_exempi
+if enable_libexif or enable_exempi
   sources += files('eog-metadata-details.c')
 endif
 
@@ -187,7 +187,7 @@ eog = executable(
   install_rpath: eog_pkglibdir
 )
 
-if have_gir
+if enable_introspection
   gir_sources = sources + headers
 
   gir_dir = join_paths(eog_pkgdatadir, 'gir-' + eog_gir_version)