Move debug callback into header and allow adding user pointer

src/VkBootstrap.cpp

@@ -16,7 +16,6 @@
 
 #include "VkBootstrap.h"
 
-#include <cstdio>
 #include <cstring>
 
 #if defined(_WIN32)
@@ -257,6 +256,7 @@ VkResult create_debug_utils_messenger(VkInstance instance,
     PFN_vkDebugUtilsMessengerCallbackEXT debug_callback,
     VkDebugUtilsMessageSeverityFlagsEXT severity,
     VkDebugUtilsMessageTypeFlagsEXT type,
+    void* user_data_pointer,
     VkDebugUtilsMessengerEXT* pDebugMessenger,
     VkAllocationCallbacks* allocation_callbacks) {
 
@@ -267,6 +267,7 @@ VkResult create_debug_utils_messenger(VkInstance instance,
 	messengerCreateInfo.messageSeverity = severity;
 	messengerCreateInfo.messageType = type;
 	messengerCreateInfo.pfnUserCallback = debug_callback;
+	messengerCreateInfo.pUserData = user_data_pointer;
 
 	PFN_vkCreateDebugUtilsMessengerEXT createMessengerFunc;
 	detail::vulkan_functions().get_inst_proc_addr(createMessengerFunc, "vkCreateDebugUtilsMessengerEXT");
@@ -289,17 +290,6 @@ void destroy_debug_utils_messenger(
 	}
 }
 
-VKAPI_ATTR VkBool32 VKAPI_CALL default_debug_callback(VkDebugUtilsMessageSeverityFlagBitsEXT messageSeverity,
-    VkDebugUtilsMessageTypeFlagsEXT messageType,
-    const VkDebugUtilsMessengerCallbackDataEXT* pCallbackData,
-    void*) {
-	auto ms = to_string_message_severity(messageSeverity);
-	auto mt = to_string_message_type(messageType);
-	printf("[%s: %s]\n%s\n", ms, mt, pCallbackData->pMessage);
-
-	return VK_FALSE;
-}
-
 namespace detail {
 bool check_layer_supported(std::vector<VkLayerProperties> const& available_layers, const char* layer_name) {
 	if (!layer_name) return false;
@@ -674,6 +664,7 @@ detail::Result<Instance> InstanceBuilder::build() const {
 		messengerCreateInfo.messageSeverity = info.debug_message_severity;
 		messengerCreateInfo.messageType = info.debug_message_type;
 		messengerCreateInfo.pfnUserCallback = info.debug_callback;
+		messengerCreateInfo.pUserData = info.debug_user_data_pointer;
 		pNext_chain.push_back(reinterpret_cast<VkBaseOutStructure*>(&messengerCreateInfo));
 	}
 
@@ -725,6 +716,7 @@ detail::Result<Instance> InstanceBuilder::build() const {
 		    info.debug_callback,
 		    info.debug_message_severity,
 		    info.debug_message_type,
+		    info.debug_user_data_pointer,
 		    &instance.debug_messenger,
 		    info.allocation_callbacks);
 		if (res != VK_SUCCESS) {
@@ -795,6 +787,10 @@ InstanceBuilder& InstanceBuilder::set_debug_callback(PFN_vkDebugUtilsMessengerCa
 	info.debug_callback = callback;
 	return *this;
 }
+InstanceBuilder& InstanceBuilder::set_debug_callback_user_data_pointer(void* user_data_pointer) {
+	info.debug_user_data_pointer = user_data_pointer;
+	return *this;
+}
 InstanceBuilder& InstanceBuilder::set_headless(bool headless) {
 	info.headless_context = headless;
 	return *this;

src/VkBootstrap.h

@@ -17,6 +17,7 @@
 #pragma once
 
 #include <cassert>
+#include <cstdio>
 
 #include <vector>
 #include <system_error>
@@ -206,6 +207,22 @@ struct SystemInfo {
 	bool debug_utils_available = false;
 };
 
+// Forward declared - check VkBoostrap.cpp for implementations
+const char* to_string_message_severity(VkDebugUtilsMessageSeverityFlagBitsEXT s);
+const char* to_string_message_type(VkDebugUtilsMessageTypeFlagsEXT s);
+
+// Default debug messenger
+// Feel free to copy-paste it into your own code, change it as needed, then call `set_debug_callback()` to use that instead
+inline VKAPI_ATTR VkBool32 VKAPI_CALL default_debug_callback(VkDebugUtilsMessageSeverityFlagBitsEXT messageSeverity,
+    VkDebugUtilsMessageTypeFlagsEXT messageType,
+    const VkDebugUtilsMessengerCallbackDataEXT* pCallbackData,
+    void*) {
+	auto ms = to_string_message_severity(messageSeverity);
+	auto mt = to_string_message_type(messageType);
+	printf("[%s: %s]\n%s\n", ms, mt, pCallbackData->pMessage);
+
+	return VK_FALSE; // Applications must return false here
+}
 
 class InstanceBuilder;
 class PhysicalDeviceSelector;
@@ -270,6 +287,8 @@ class InstanceBuilder {
 	InstanceBuilder& use_default_debug_messenger();
 	// Provide a user defined debug callback.
 	InstanceBuilder& set_debug_callback(PFN_vkDebugUtilsMessengerCallbackEXT callback);
+	// Sets the void* to use in the debug messenger - only useful with a custom callback
+	InstanceBuilder& set_debug_callback_user_data_pointer(void* user_data_pointer);
 	// Set what message severity is needed to trigger the callback.
 	InstanceBuilder& set_debug_messenger_severity(VkDebugUtilsMessageSeverityFlagsEXT severity);
 	// Add a message severity to the list that triggers the callback.
@@ -310,13 +329,14 @@ class InstanceBuilder {
 		VkInstanceCreateFlags flags = 0;
 		std::vector<VkBaseOutStructure*> pNext_elements;
 
-		// debug callback
+		// debug callback - use the default so it is not nullptr
-		PFN_vkDebugUtilsMessengerCallbackEXT debug_callback = nullptr;
+		PFN_vkDebugUtilsMessengerCallbackEXT debug_callback = default_debug_callback;
 		VkDebugUtilsMessageSeverityFlagsEXT debug_message_severity =
 		    VK_DEBUG_UTILS_MESSAGE_SEVERITY_WARNING_BIT_EXT | VK_DEBUG_UTILS_MESSAGE_SEVERITY_ERROR_BIT_EXT;
 		VkDebugUtilsMessageTypeFlagsEXT debug_message_type =
 		    VK_DEBUG_UTILS_MESSAGE_TYPE_GENERAL_BIT_EXT | VK_DEBUG_UTILS_MESSAGE_TYPE_VALIDATION_BIT_EXT |
 		    VK_DEBUG_UTILS_MESSAGE_TYPE_PERFORMANCE_BIT_EXT;
+		void* debug_user_data_pointer = nullptr;
 
 		// validation features
 		std::vector<VkValidationCheckEXT> disabled_validation_checks;

tests/bootstrap_tests.cpp

@@ -3,11 +3,8 @@
 #include <catch2/catch.hpp>
 
 vkb::Instance get_instance(uint32_t minor_version = 0) {
-	auto instance_ret = vkb::InstanceBuilder()
+	auto instance_ret =
-	                        .request_validation_layers()
+	    vkb::InstanceBuilder().request_validation_layers().require_api_version(1, minor_version).build();
-	                        .require_api_version(1, minor_version)
-	                        .use_default_debug_messenger()
-	                        .build();
 	REQUIRE(instance_ret.has_value());
 	return instance_ret.value();
 }
@@ -16,7 +13,6 @@ vkb::Instance get_headless_instance(uint32_t minor_version = 0) {
 	                        .request_validation_layers()
 	                        .require_api_version(1, minor_version)
 	                        .set_headless()
-	                        .use_default_debug_messenger()
 	                        .build();
 	REQUIRE(instance_ret.has_value());
 	return instance_ret.value();