Update comments and explicitly request required extensions/GPU featur…

…es for debugPrintfEXT

(cherry picked from commit 3365c7d974ae1cb7222cf35fdbe82accfa3fd926)

samples/extensions/shader_debugprintf/shader_debugprintf.cpp

@@ -44,6 +44,7 @@ ShaderDebugPrintf::ShaderDebugPrintf()
 	title = "Shader debugprintf";
 
 	add_device_extension(VK_KHR_SHADER_NON_SEMANTIC_INFO_EXTENSION_NAME);
+	add_device_extension(VK_KHR_TIMELINE_SEMAPHORE_EXTENSION_NAME);
 }
 
 ShaderDebugPrintf::~ShaderDebugPrintf()
@@ -68,6 +69,14 @@ ShaderDebugPrintf::~ShaderDebugPrintf()
 
 void ShaderDebugPrintf::request_gpu_features(vkb::PhysicalDevice &gpu)
 {
+	// debugPrintfEXT requires fragmentStoresAndAtomics, vertexPipelineStoresAndAtomics, and shaderInt64
+	gpu.get_mutable_requested_features().fragmentStoresAndAtomics       = VK_TRUE;
+	gpu.get_mutable_requested_features().vertexPipelineStoresAndAtomics = VK_TRUE;
+	gpu.get_mutable_requested_features().shaderInt64                    = VK_TRUE;
+
+	// debugPrintfEXT also requires the timelineSemaphore feature in the timelineSemaphore features struct
+	REQUEST_REQUIRED_FEATURE(gpu, VkPhysicalDeviceTimelineSemaphoreFeatures, VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_TIMELINE_SEMAPHORE_FEATURES, timelineSemaphore);
+
 	// Enable anisotropic filtering if supported
 	if (gpu.get_features().samplerAnisotropy)
 	{
@@ -467,8 +476,10 @@ std::unique_ptr<vkb::Instance> ShaderDebugPrintf::create_instance(bool headless)
 		return VulkanSample::create_instance(headless);
 	}
 
-	// Run remainder of this custom create_instance() (without layer settings support) and return
+	// As a fallack, run remainder of this custom create_instance() override (without layer settings support) and return
 	std::vector<const char *> enabled_extensions;
+	enabled_extensions.push_back(VK_KHR_SURFACE_EXTENSION_NAME);
+
 	for (const char *extension_name : window->get_required_surface_extensions())
 	{
 		enabled_extensions.push_back(extension_name);
@@ -492,7 +503,7 @@ std::unique_ptr<vkb::Instance> ShaderDebugPrintf::create_instance(bool headless)
 	app_info.pEngineName      = "Vulkan Samples";
 	app_info.apiVersion       = debugprintf_api_version;
 
-	// Legacy extension for configuring validation layer features using VkValidationFeaturesEXT
+	// Enable VK_EXT_validation_features extension for configuring validation layer features using VkValidationFeaturesEXT
 	enabled_extensions.push_back(VK_EXT_VALIDATION_FEATURES_EXTENSION_NAME);
 
 	// Shader printf is a feature of the validation layers that needs to be enabled