CMake: Check for the needed lgi dependency

We only need lgi for running, not for building. This means that our lgi
dependency is easily missed. This commit makes this dependency more explicit.

Signed-off-by: Uli Schlachter <psychon@znc.in>

CMakeLists.txt

@@ -103,6 +103,10 @@ target_link_libraries(${PROJECT_AWE_NAME}
     ${AWESOME_REQUIRED_LDFLAGS}
     ${AWESOME_OPTIONAL_LDFLAGS})
 
+# check for lgi and the needed gobject introspection files
+add_custom_target(lgi-check ALL
+    COMMAND ${SOURCE_DIR}/build-utils/lgi-check.sh)
+
 # atoms
 file(MAKE_DIRECTORY ${BUILD_DIR}/common)
 add_custom_command(

build-utils/lgi-check.sh

@@ -0,0 +1,31 @@
+#!/bin/sh
+
+die()
+{
+	exec >&2
+	echo
+	echo
+	echo "       WARNING"
+	echo "       ======="
+	echo
+	echo " The lgi check failed."
+	echo " The Lua GObject introspection package is just a runtime dependency, so it is not"
+	echo " necessary for building awesome. However, awesome needs it to run."
+	echo " Add AWESOME_IGNORE_LGI=1 to your environment to continue."
+	echo
+	echo
+	if [ "x$AWESOME_IGNORE_LGI" = "x1" ]
+	then
+		exit 0
+	fi
+	exit 1
+}
+
+# Check if we have lgi
+lua -e 'require("lgi")' || die
+
+# Check the version number
+lua -e 'if tonumber(string.match(require("lgi.version"), "(%d%.%d)")) <= 0.5 then error("lgi too old, need at least version 0.6.1") end' || die
+
+# Check for the needed gi files
+lua -e 'l = require("lgi") assert(l.cairo, l.Pango, l.PangoCairo)' || die