diff --git a/except.hpp b/except.hpp
index ccff147..a4c0367 100644
--- a/except.hpp
+++ b/except.hpp
@@ -21,12 +21,46 @@
 #include "./vk.hpp"
 
 #include <exception>
+#include <functional>
+#include <type_traits>
+
 
 namespace cruft::vk {
     class error : public std::exception {
     public:
         static void try_code (VkResult);
         static void throw_code [[noreturn]] (VkResult);
+
+
+        /// invokes a supplied function with the given arguments and tests
+        /// that it returns indicating success using try_code.
+        template <
+            typename FuncT,
+            typename ...Args
+        >
+        static void
+        try_func (FuncT &&func, Args &&...args)
+        {
+            static_assert(std::is_same_v<
+                std::result_of_t<FuncT(Args...)>,
+                VkResult
+            >);
+
+            try_code (std::invoke (func, std::forward<Args> (args)...));
+        }
+
+
+        /// requests a ValueT using a invokable FuncT with arguments
+        /// [Args..., &ValueT] and returns the result after testing for
+        /// success.
+        template <typename ValueT, typename FuncT, typename ...Args>
+        static ValueT
+        try_query (FuncT &&func, Args &&...args)
+        {
+            ValueT value;
+            try_func (func, std::forward<Args> (args)..., &value);
+            return value;
+        }
     };
 
 
diff --git a/fence.cpp b/fence.cpp
index 8e14692..8db0cb4 100644
--- a/fence.cpp
+++ b/fence.cpp
@@ -41,7 +41,9 @@ fence::reset (const device &dev, fence *first, fence *last)
 {
     CHECK_LE (first, last);
 
-    vkResetFences (dev.id (), trunc_cast<uint32_t> (last - first), &first->id ());
+    cruft::vk::error::try_func (
+        &vkResetFences, dev.id (), trunc_cast<uint32_t> (last - first), &first->id ()
+    );
 }
 
 
@@ -51,7 +53,9 @@ fence::wait (const device &d, fence *first, fence *last, uint64_t timeout)
 {
     CHECK_LE (first, last);
 
-    vkWaitForFences (d.id (), trunc_cast<uint32_t> (last - first), &first->id (), VK_FALSE, timeout);
+    cruft::vk::error::try_func (
+        &vkWaitForFences, d.id (), trunc_cast<uint32_t> (last - first), &first->id (), VK_FALSE, timeout
+    );
 }
 
 
@@ -61,5 +65,7 @@ fence::wait_all (const device &d, fence *first, fence *last, uint64_t timeout)
 {
     CHECK_LE (first, last);
 
-    vkWaitForFences (d.id (), trunc_cast<uint32_t> (last - first), &first->id (), VK_TRUE, timeout);
+    cruft::vk::error::try_func (
+        &vkWaitForFences, d.id (), trunc_cast<uint32_t> (last - first), &first->id (), VK_TRUE, timeout
+    );
 }
diff --git a/physical_device.cpp b/physical_device.cpp
index 1fd792b..e828e7c 100644
--- a/physical_device.cpp
+++ b/physical_device.cpp
@@ -59,6 +59,19 @@ physical_device::features (void) const
 }
 
 
+//-----------------------------------------------------------------------------
+VkSurfaceCapabilitiesKHR
+physical_device::surface_capabilities (VkSurfaceKHR surface) const
+{
+    VkSurfaceCapabilitiesKHR value;
+    error::try_func (
+        &vkGetPhysicalDeviceSurfaceCapabilitiesKHR, id (), surface, &value
+    );
+
+    return value;
+}
+
+
 ///////////////////////////////////////////////////////////////////////////////
 std::vector<VkQueueFamilyProperties>
 physical_device::queue_families (void) const
diff --git a/physical_device.hpp b/physical_device.hpp
index 0e12bf3..f943022 100644
--- a/physical_device.hpp
+++ b/physical_device.hpp
@@ -33,6 +33,7 @@ namespace cruft::vk {
 
         VkPhysicalDeviceProperties properties (void) const;
         VkPhysicalDeviceFeatures features (void) const;
+        VkSurfaceCapabilitiesKHR surface_capabilities (VkSurfaceKHR) const;
 
         std::vector<VkQueueFamilyProperties> queue_families (void) const;
 
diff --git a/tools/hello.cpp b/tools/hello.cpp
index 0ea1394..8810895 100644
--- a/tools/hello.cpp
+++ b/tools/hello.cpp
@@ -95,13 +95,17 @@ main (void)
         VkDebugReportCallbackEXT callback;
         VkDebugReportCallbackCreateInfoEXT debug_info {};
         debug_info.sType = VK_STRUCTURE_TYPE_DEBUG_REPORT_CREATE_INFO_EXT;
-        debug_info.flags = VK_DEBUG_REPORT_ERROR_BIT_EXT | VK_DEBUG_REPORT_WARNING_BIT_EXT;
+        debug_info.flags = VK_DEBUG_REPORT_INFORMATION_BIT_EXT |
+                           VK_DEBUG_REPORT_WARNING_BIT_EXT |
+                           VK_DEBUG_REPORT_PERFORMANCE_WARNING_BIT_EXT |
+                           VK_DEBUG_REPORT_ERROR_BIT_EXT |
+                           VK_DEBUG_REPORT_DEBUG_BIT_EXT;
         debug_info.pfnCallback = vk_debug_callback;
 
         auto func = (decltype(&vkCreateDebugReportCallbackEXT))vkGetInstanceProcAddr (instance.id (),"vkCreateDebugReportCallbackEXT");
 
-        cruft::vk::error::try_code (
-            func (instance.id (), &debug_info, nullptr, &callback)
+        cruft::vk::error::try_func (
+            func, instance.id (), &debug_info, nullptr, &callback
         );
     }
 
@@ -117,7 +121,9 @@ main (void)
     std::vector<VkSurfaceFormatKHR> surface_formats;
     std::vector<VkPresentModeKHR> present_modes;
 
-    vkGetPhysicalDeviceSurfaceCapabilitiesKHR (pdevice.id (), surface, &surface_capabilities);
+    cruft::vk::error::try_func (
+        &vkGetPhysicalDeviceSurfaceCapabilitiesKHR, pdevice.id (), surface, &surface_capabilities
+    );
     {
         uint32_t format_count = 0;
         cruft::vk::error::try_code (
@@ -150,7 +156,9 @@ main (void)
             graphics_queue_id = i;
 
         VkBool32 present_support = false;
-        vkGetPhysicalDeviceSurfaceSupportKHR (pdevice.id (), i, surface, &present_support);
+        cruft::vk::error::try_func (
+            &vkGetPhysicalDeviceSurfaceSupportKHR, pdevice.id (), i, surface, &present_support
+        );
         if (present_support)
             present_queue_id = i;
     }
@@ -515,7 +523,7 @@ main (void)
 
         vkCmdEndRenderPass (command_buffers[i]);
 
-        vkEndCommandBuffer (command_buffers[i]);
+        cruft::vk::error::try_func (&vkEndCommandBuffer, command_buffers[i]);
     };
 
     VkSemaphoreCreateInfo semaphore_info {};
@@ -560,7 +568,6 @@ main (void)
     dependency.srcSubpass = VK_SUBPASS_EXTERNAL;
     dependency.dstSubpass = 0;
     dependency.srcStageMask = VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT;
-    dependency.srcAccessMask = 0;
     dependency.dstStageMask = VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT;
     dependency.dstAccessMask = VK_ACCESS_COLOR_ATTACHMENT_READ_BIT | VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT;
     render_pass_info.dependencyCount = 1;
@@ -577,14 +584,14 @@ main (void)
     present_info.pImageIndices = &image_index;
     present_info.pResults = nullptr;
 
-    vkQueuePresentKHR (present_queue.id (), &present_info);
+    cruft::vk::error::try_func (&vkQueuePresentKHR, present_queue.id (), &present_info);
 
     LOG_INFO ("entering runloop");
     while (!glfwWindowShouldClose (window)) {
         glfwPollEvents ();
     }
 
-    vkDeviceWaitIdle (ldevice.id ());
+    cruft::vk::error::try_func (&vkDeviceWaitIdle, ldevice.id ());
 
     LOG_INFO ("terminating glfw");
     glfwDestroyWindow (window);