winex11: Specify a default vulkan driver if one not found at build time

dlls/winex11.drv/vulkan.c

@@ -43,10 +43,12 @@
 #include "wine/vulkan_driver.h"
 
 WINE_DEFAULT_DEBUG_CHANNEL(vulkan);
-
-#ifdef SONAME_LIBVULKAN
 WINE_DECLARE_DEBUG_CHANNEL(fps);
 
+#ifndef SONAME_LIBVULKAN
+#define SONAME_LIBVULKAN ""
+#endif
+
 static pthread_mutex_t vulkan_mutex;
 
 static XContext vulkan_hwnd_context;
@@ -107,14 +109,23 @@ static void *vulkan_handle;
 
 static void wine_vk_init(void)
 {
-    init_recursive_mutex(&vulkan_mutex);
+    const char *libvulkan_candidates[] = {SONAME_LIBVULKAN,
+                                          "libvulkan.so.1",
+                                          "libvulkan.so",
+                                          NULL};
+    int i;
+
+    for (i=0; libvulkan_candidates[i] && !vulkan_handle; i++)
+        vulkan_handle = dlopen(libvulkan_candidates[i], RTLD_NOW);
 
-    if (!(vulkan_handle = dlopen(SONAME_LIBVULKAN, RTLD_NOW)))
+    if (!vulkan_handle)
     {
-        ERR("Failed to load %s.\n", SONAME_LIBVULKAN);
+        ERR("Failed to load vulkan library\n");
         return;
     }
 
+    init_recursive_mutex(&vulkan_mutex);
+
 #define LOAD_FUNCPTR(f) if (!(p##f = dlsym(vulkan_handle, #f))) goto fail
 #define LOAD_OPTIONAL_FUNCPTR(f) p##f = dlsym(vulkan_handle, #f)
     LOAD_FUNCPTR(vkCreateInstance);
@@ -734,20 +745,3 @@ const struct vulkan_funcs *get_vulkan_driver(UINT version)
     return NULL;
 }
 
-#else /* No vulkan */
-
-const struct vulkan_funcs *get_vulkan_driver(UINT version)
-{
-    ERR("Wine was built without Vulkan support.\n");
-    return NULL;
-}
-
-void wine_vk_surface_destroy(HWND hwnd)
-{
-}
-
-void vulkan_thread_detach(void)
-{
-}
-
-#endif /* SONAME_LIBVULKAN */