emacs-29 7e1012765c4: Fix libwebp check for some webp installations

[Po Lu]

branch: emacs-29
commit 7e1012765c40a10a8a051c39566778913dc7e224
Author: Po Lu <luangruo@yahoo.com>
Commit: Po Lu <luangruo@yahoo.com>

    Fix libwebp check for some webp installations
    
    * configure.ac: Look for WebPGetInfo; if it is not there, look
    for libwebpdecoder as well.  (bug#61988)
---
 configure.ac | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/configure.ac b/configure.ac
index bc7e61048c3..ac93d003b70 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2806,6 +2806,25 @@ if test "${with_webp}" != "no"; then
       WEBP_MODULE="libwebpdemux >= $WEBP_REQUIRED"
 
       EMACS_CHECK_MODULES([WEBP], [$WEBP_MODULE])
+
+      # WebPGetInfo is sometimes not present inside libwebpdemux, so
+      # if it does not link, also check for libwebpdecoder.
+
+      OLD_CFLAGS=$CFLAGS
+      OLD_LIBS=$LIBS
+      CFLAGS="$CFLAGS $WEBP_CFLAGS"
+      LIBS="$LIBS $WEBP_LIBS"
+
+      AC_CHECK_FUNC([WebPGetInfo], [],
+        [WEBP_MODULE="$WEBP_MODULE libwebpdecoder >= $WEBP_REQUIRED"
+        HAVE_WEBP=no
+        AS_UNSET([WEBP_LIBS])
+        AS_UNSET([WEBP_CFLAGS])
+        EMACS_CHECK_MODULES([WEBP], [$WEBP_MODULE])])
+
+      CFLAGS=$OLD_CFLAGS
+      LIBS=$OLD_LIBS
+
       AC_SUBST([WEBP_CFLAGS])
       AC_SUBST([WEBP_LIBS])
    fi