From: Roland Hieber <r.hieber@pengutronix.de>
Date: Mon, 17 Jul 2017 11:35:32 +0200
Subject: [PATCH] configure.ac: fix --disable-FEATURE actually enabling the
 feature

Forwarded: https://bugs.freedesktop.org/show_bug.cgi?id=101818

A frequently seen antipattern is to use
AC_ARG_ENABLE(feature, help, action-if-given, action-if-not-given) as
AC_ARG_ENABLE(feature, help, action-if-enabled, action-if-disabled).
However, action-if-given is also evaluated for --disable-FEATURE (with
enableval=no), which results in --disable-FEATURE and --enable-FEATURE
doing the same in this case.

Rewrite the single-precision, fixedpoint and cmyk arguments accordingly
so the user is not confused if they explicitely want to disable those
options.

Signed-off-by: Roland Hieber <r.hieber@pengutronix.de>
---
 configure.ac | 32 ++++++++++++++++++++++++++------
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/configure.ac b/configure.ac
index 98d497a973b6..40a78d90d72d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -122,16 +122,36 @@ else
 fi
 
 AC_ARG_ENABLE(single-precision,
-[  --enable-single-precision     use single precision arithmetic (instead of double precision) in the Splash backend],
-AC_DEFINE(USE_FLOAT,      [1], [Use single precision arithmetic in the Splash backend]))
+        AC_HELP_STRING([--enable-single-precision],
+                       [use single precision arithmetic (instead of double
+                        precision) in the Splash backend]),
+        enable_single_precision=$enableval,
+        enable_single_precision=no)
+if test x$enable_single_precision != xno; then
+        AC_DEFINE(USE_FLOAT, [1], [Use single precision arithmetic in the Splash backend])
+fi
 
 AC_ARG_ENABLE(fixedpoint,
-[  --enable-fixedpoint     use fixed point (instead of double precision) arithmetic in the Splash backend],
-AC_DEFINE(USE_FIXEDPOINT, [1], [Use fixed point arithmetic in the Splash backend]))
+        AC_HELP_STRING([--enable-fixedpoint],
+                       [use fixed point (instead of double precision) arithmetic
+                        in the Splash backend]),
+        enable_fixedpoint=$enableval,
+        enable_fixedpoint=no)
+if test x$enable_fixedpoint != xno; then
+        if test x$enable_single_precision != xno; then
+                AC_MSG_ERROR([Choose only one of --enable-single-precision or --enable-fixedpoint!])
+        fi
+        AC_DEFINE(USE_FIXEDPOINT, [1], [Use fixed point arithmetic in the Splash backend])
+fi
 
 AC_ARG_ENABLE(cmyk,
-[  --enable-cmyk           Include support for CMYK rasterization],
-AC_DEFINE(SPLASH_CMYK, [1], [Include support for CMYK rasterization]))
+        AC_HELP_STRING([--enable-cmyk],
+                       [Include support for CMYK rasterization]),
+        enable_cmyk=$enableval,
+        enable_cmyk=no)
+if test x$enable_cmyk != xno; then
+        AC_DEFINE(SPLASH_CMYK, [1], [Include support for CMYK rasterization])
+fi
 
 dnl Relocation support
 AC_ARG_ENABLE(relocatable,