load: hook vkCreateInstance as a means to setup global vtables

CMakeLists.txt

@@ -66,6 +66,7 @@ list (APPEND VK_LOAD_SOURCES
     ${GENERATED_PREFIX}/load/vtable.hpp
     ${GENERATED_PREFIX}/load/dispatch.cpp
     load/dispatch.hpp
+    load/init.cpp
     load/ostream.cpp
     load/ostream.hpp
     load/vendor.hpp

load/init.cpp

@@ -0,0 +1,50 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * Copyright 2019 Danny Robson <danny@nerdcruft.net>
+ */
+
+
+#include <cruft/vk/load/vtable.hpp>
+#include <cruft/vk/load/vendor.hpp>
+
+#include <vector>
+
+
+///////////////////////////////////////////////////////////////////////////////
+// We need to ensure the tables are loaded before anything much gets called.
+//
+// Given we have a global vtable we'll install a default table that hooks the
+// function(s) that a client will call first off. This function will:
+//   * find the various ICDs on the system,
+//   * install a vtable that forwards calls by default,
+//   * and then forwards the current call on to this newly installed vtable
+
+
+///////////////////////////////////////////////////////////////////////////////
+static VkResult setup_vtables (
+    const VkInstanceCreateInfo* pCreateInfo,
+    const VkAllocationCallbacks* pAllocator,
+    VkInstance* pInstance
+) {
+    static auto libraries = cruft::vk::load::enumerate ();
+    static cruft::vk::load::vendor v (libraries[0]);
+
+    cruft::vk::load::i_table = &v.itable;
+    cruft::vk::load::v_table = &v.vtable;
+
+    return cruft::vk::load::i_table->vkCreateInstance (pCreateInfo, pAllocator, pInstance);
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+static cruft::vk::load::instance_table const initialiser {
+    .vkCreateInstance = setup_vtables,
+};
+
+
+//-----------------------------------------------------------------------------
+cruft::vk::load::instance_table const *cruft::vk::load::i_table = &initialiser;
+

load/vtable.cpp

@@ -5,4 +5,3 @@ using cruft::vk::load::instance_table;
 
 ///////////////////////////////////////////////////////////////////////////////
 cruft::vk::load::vendor_table const *cruft::vk::load::v_table = nullptr;
-cruft::vk::load::instance_table const *cruft::vk::load::i_table = nullptr;

tools/info.cpp

@@ -27,22 +27,13 @@
 int
 main (int, char**)
 {
-    std::cout << "[ ";
-    for (auto const &i: cruft::vk::load::enumerate ()) {
-        cruft::vk::load::vendor v (i);
-        cruft::vk::load::i_table = &v.itable;
-        cruft::vk::load::v_table = &v.vtable;
-
     cruft::vk::instance instance;
 
-        std::cout
-            << "{ vendor: " << i
-            << ", available_layers: [ "
+    std::cout << "[ "
+        << "available_layers: [ "
             << cruft::make_infix (cruft::vk::instance::available_layers ())
         << " ] }"
         << ", instance: " << instance
         << ", devices: [ " << cruft::make_infix (cruft::vk::physical_device::find (instance)) << " ], "
-            << " }, ";
-    }
-    std::cout << " ]\n";
+        << " } ]\n";
 }