[PATCH libinput] meson: point users to disabled documentation when dot/doxygen is missing

[Peter Hutterer]

Especially dot is hard to find for some users, so provide the solution to
their problems right there in the error message.

And because users are likely to just copy/paste, remove the disable-libwacom
option. Save them from themselves...

Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
 doc/building.dox |  5 ++++-
 meson.build      | 11 +++++++++--
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/doc/building.dox b/doc/building.dox
index 8e302e0d..ef7793b0 100644
--- a/doc/building.dox
+++ b/doc/building.dox
@@ -28,9 +28,12 @@ $> sudo udevadm hwdb --update
 
 Additional options may also be specified. For example:
 @code
-$> meson --prefix=/usr -Ddocumentation=false -Dlibwacom=false builddir/
+$> meson --prefix=/usr -Ddocumentation=false builddir/
 @endcode
 
+We recommend that users disable the documentation, it's not usually required
+for testing and reduces the number of dependencies needed.
+
 The ```prefix``` or other options can be changed later with the
 ```mesonconf``` command. For example:
 @code
diff --git a/meson.build b/meson.build
index 58ef31a4..fcd3d8c4 100644
--- a/meson.build
+++ b/meson.build
@@ -254,7 +254,15 @@ meson.add_install_script('src/libinput-restore-selinux-context.sh',
 ############ documentation ############
 
 if get_option('documentation')
-	doxygen = find_program('doxygen')
+	doxygen = find_program('doxygen', required : false)
+	if not doxygen.found()
+		error('Program "doxygen" not found or not executable. Try building with -Ddocumentation=false')
+	endif
+	dot = find_program('dot', required : false)
+	if not dot.found()
+		error('Program "dot" not found or not executable. Try building with -Ddocumentation=false')
+	endif
+
 	doxygen_version_cmd = run_command(doxygen.path(), '--version')
 	if doxygen_version_cmd.returncode() != 0
 		error('Command "doxygen --version" failed.')
@@ -263,7 +271,6 @@ if get_option('documentation')
 	if doxygen_version.version_compare('< 1.8.3')
 		error('doxygen needs to be at least version 1.8.3 (have @0@)'.format(doxygen_version))
 	endif
-	dot = find_program('dot')
 	grep = find_program('grep')
 	dot_version_cmd = run_command(dot.path(), '-V')
 	if dot_version_cmd.returncode() != 0
-- 
2.14.3