vulkan: support not having glslc available for building vulkan plugin

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/6980>

subprojects/gst-plugins-bad/ext/vulkan/gstvulkan.c

@@ -31,14 +31,17 @@
 
 #include "vksink.h"
 #include "vkupload.h"
+#include "vkdownload.h"
+#include "vkdeviceprovider.h"
+#include "gstvulkanelements.h"
+
+#if defined(HAVE_GLSLC)
 #include "vkimageidentity.h"
 #include "vkcolorconvert.h"
 #include "vkshaderspv.h"
-#include "vkdownload.h"
 #include "vkviewconvert.h"
-#include "vkdeviceprovider.h"
-#include "gstvulkanelements.h"
 #include "vkoverlaycompositor.h"
+#endif
 
 #if GST_VULKAN_HAVE_VIDEO_EXTENSIONS
 #include "vkh264dec.h"
@@ -57,7 +60,7 @@ plugin_init (GstPlugin * plugin)
   ret |= GST_ELEMENT_REGISTER (vulkanupload, plugin);
 
   ret |= GST_ELEMENT_REGISTER (vulkandownload, plugin);
-
+#if defined(HAVE_GLSLC)
   ret |= GST_ELEMENT_REGISTER (vulkancolorconvert, plugin);
 
   ret |= GST_ELEMENT_REGISTER (vulkanimageidentity, plugin);
@@ -67,7 +70,7 @@ plugin_init (GstPlugin * plugin)
   ret |= GST_ELEMENT_REGISTER (vulkanviewconvert, plugin);
 
   ret |= GST_ELEMENT_REGISTER (vulkanoverlaycompositor, plugin);
-
+#endif
 #if GST_VULKAN_HAVE_VIDEO_EXTENSIONS
   GST_ELEMENT_REGISTER (vulkanh264dec, plugin);
   GST_ELEMENT_REGISTER (vulkanh265dec, plugin);

subprojects/gst-plugins-bad/ext/vulkan/meson.build

@@ -10,42 +10,53 @@ if not gstvulkan_dep.found()
   endif
 endif
 
-# Should already have checked for this
-assert(glslc.found(), 'Expected glslc to be available')
-
-subdir('shaders')
+extra_deps = []
+extra_args = []
 
 vulkan_sources = files(
   'gstvulkan.c',
   'gstvulkanelement.c',
-  'vkcolorconvert.c',
   'vkdownload.c',
   'vkdeviceprovider.c',
-  'vkimageidentity.c',
-  'vkshaderspv.c',
   'vksink.c',
   'vkupload.c',
+)
+vulkan_plugin_enums = []
+
+glslc = find_program('glslc', required: get_option('vulkan'))
+if not glslc.found()
+  if get_option('vulkan').enabled()
+    error('GStreamer Vulkan plugin required via options, but glslc was not found.')
+  else
+    subdir_done()
+  endif
+  vulkan_compiled_shader_sources = []
+else
+  extra_args += ['-DHAVE_GLSLC']
+  subdir('shaders')
+
+  vulkan_sources += files(
+    'vkcolorconvert.c',
+    'vkimageidentity.c',
+    'vkshaderspv.c',
     'vkviewconvert.c',
     'vkoverlaycompositor.c',
   )
-
   vulkan_plugin_enum_headers = files(
     'vkviewconvert.h',
   )
+  vulkan_plugin_enums += gnome.mkenums_simple('gstvulkan-plugins-enumtypes',
+      sources : vulkan_plugin_enum_headers,
+      body_prefix : '#ifdef HAVE_CONFIG_H\n#include "config.h"\n#endif',
+      header_prefix : '#include <gst/gst.h>')
+endif
 
-extra_deps = []
-extra_args = []
 if vulkan_conf.get('GST_VULKAN_HAVE_VIDEO_EXTENSIONS') == 1
   vulkan_sources += files('vkh264dec.c', 'vkh265dec.c')
   extra_deps += gstcodecs_dep
   extra_args += ['-DGST_USE_UNSTABLE_API']
 endif
 
-vulkan_plugin_enums = gnome.mkenums_simple('gstvulkan-plugins-enumtypes',
-    sources : vulkan_plugin_enum_headers,
-    body_prefix : '#ifdef HAVE_CONFIG_H\n#include "config.h"\n#endif',
-    header_prefix : '#include <gst/gst.h>')
-
 gstvulkan_plugin = library('gstvulkan',
   vulkan_sources, vulkan_compiled_shader_sources, vulkan_plugin_enums,
   c_args : gst_plugins_bad_args + extra_args,

subprojects/gst-plugins-bad/gst-libs/gst/vulkan/meson.build

@@ -298,11 +298,7 @@ if not vulkan_windowing
   endif
 endif
 
-# Only needed for the vulkan plugin, but doesn't make sense to build
-# anything else vulkan related if we are not going to build the plugin
-glslc = find_program('glslc', required: get_option('vulkan'))
-
-if not vulkan_dep.found() or not has_vulkan_header or not glslc.found()
+if not vulkan_dep.found() or not has_vulkan_header
   if get_option('vulkan').enabled()
     error('GStreamer Vulkan integration required via options, but needed dependencies not found.')
   else