configure: Improve Vulkan detection

1. Output Vulkan status in summary
2. Add missing "test" call
3. Check for glslc

The glslc check will be necessary later for the code that automatically
compiles the Vulkan glsl source to Spir-V.
Nothing happens if glslc is not available - unless you modify the glsl.

diff --git a/configure.ac b/configure.ac
index df3a187a077d8fbe811e831e3004cd274ad687cb..8093384b2aa351980a9bd202ae36019a6d808929 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -1321,27 +1321,29 @@ fi
 
 # Check for Vulkan support.
 
-have_vulkan="no"
 if test "x$enable_vulkan" != "xno"; then
       vulkan_error=""
       AC_CHECK_HEADER([vulkan/vulkan.h], [], [vulkan_error="Vulkan header not found"])
       AC_CHECK_LIB([vulkan], [vkCreateInstance], [], [vulkan_error="Vulkan library not found"])
-      if "x$vulkan_error" != "x"; then
+      if test "x$vulkan_result" != "x"; then
           if "x$enable_vulkan" = "xyes"; then
               AC_MSG_ERROR($vulkan_error)
           else
               AC_MSG_WARN($vulkan_error)
           fi
+          vulkan_result="no ($vulkan_error)"
       else
           GDK_EXTRA_LIBS="-lvulkan"
-          have_vulkan="yes"
           GDK_WINDOWING="$GDK_WINDOWING
 #define GDK_WINDOWING_VULKAN"
+          AC_PATH_PROG([GLSLC], [glslc])
+          vulkan_result="yes"
       fi
 else
       AC_MSG_WARN(Vulkan support explicitly disabled)
+      vulkan_result="no (Vulkan support explicitly disabled)"
 fi
-AM_CONDITIONAL(HAVE_VULKAN, test "$have_vulkan" = "yes")
+AM_CONDITIONAL(HAVE_VULKAN, test "$vulkan_result" = "yes")
 
 # Check for Pango flags
 
@@ -2063,6 +2065,7 @@ echo "        GDK backends:         $GDK_BACKENDS"
 if test "$enable_x11_backend" = "yes"; then
 echo "        X11 extensions:       $X_EXTENSIONS"
 fi
+echo "        Vulkan support:       $vulkan_result"
 echo "        Print backends:       $PRINT_BACKENDS"
 echo "        Dynamic modules:      $build_dynamic_modules"
 echo "        Included immodules:   $included_immodules"