03_physical_device_selection.diff

diff --git a/../steps/02_validation_layers/main.go b/../steps/03_physical_device_selection/main.go
index a9bf827..d3ac8e6 100644
--- a/../steps/02_validation_layers/main.go
+++ b/../steps/03_physical_device_selection/main.go
@@ -15,12 +15,22 @@ var validationLayers = []string{"VK_LAYER_KHRONOS_validation"}
 
 const enableValidationLayers = true
 
+type QueueFamilyIndices struct {
+	GraphicsFamily *int
+}
+
+func (i *QueueFamilyIndices) IsComplete() bool {
+	return i.GraphicsFamily != nil
+}
+
 type HelloTriangleApplication struct {
 	window *sdl.Window
 	loader core.Loader
 
 	instance       core1_0.Instance
 	debugMessenger ext_debug_utils.DebugUtilsMessenger
+
+	physicalDevice core1_0.PhysicalDevice
 }
 
 func (app *HelloTriangleApplication) Run() error {
@@ -49,7 +59,7 @@ func (app *HelloTriangleApplication) initWindow() error {
 	}
 	app.window = window
 
-	app.loader, err = core.CreateSystemLoader()
+	app.loader, err = core.CreateLoaderFromProcAddr(sdl.VulkanGetVkGetInstanceProcAddr())
 	if err != nil {
 		return err
 	}
@@ -63,7 +73,12 @@ func (app *HelloTriangleApplication) initVulkan() error {
 		return err
 	}
 
-	return app.setupDebugMessenger()
+	err = app.setupDebugMessenger()
+	if err != nil {
+		return err
+	}
+
+	return app.pickPhysicalDevice()
 }
 
 func (app *HelloTriangleApplication) mainLoop() error {
@@ -179,11 +194,62 @@ func (app *HelloTriangleApplication) setupDebugMessenger() error {
 	return nil
 }
 
+func (app *HelloTriangleApplication) pickPhysicalDevice() error {
+	physicalDevices, _, err := app.instance.EnumeratePhysicalDevices()
+	if err != nil {
+		return err
+	}
+
+	for _, device := range physicalDevices {
+		if app.isDeviceSuitable(device) {
+			app.physicalDevice = device
+			break
+		}
+	}
+
+	if app.physicalDevice == nil {
+		return errors.New("failed to find a suitable GPU!")
+	}
+
+	return nil
+}
+
+func (app *HelloTriangleApplication) isDeviceSuitable(device core1_0.PhysicalDevice) bool {
+	indices, err := app.findQueueFamilies(device)
+	if err != nil {
+		return false
+	}
+
+	return indices.IsComplete()
+}
+
+func (app *HelloTriangleApplication) findQueueFamilies(device core1_0.PhysicalDevice) (QueueFamilyIndices, error) {
+	indices := QueueFamilyIndices{}
+	queueFamilies := device.QueueFamilyProperties()
+
+	for queueFamilyIdx, queueFamily := range queueFamilies {
+		if (queueFamily.QueueFlags & core1_0.QueueGraphics) != 0 {
+			indices.GraphicsFamily = new(int)
+			*indices.GraphicsFamily = queueFamilyIdx
+		}
+
+		if indices.IsComplete() {
+			break
+		}
+	}
+
+	return indices, nil
+}
+
 func (app *HelloTriangleApplication) logDebug(msgType ext_debug_utils.DebugUtilsMessageTypeFlags, severity ext_debug_utils.DebugUtilsMessageSeverityFlags, data *ext_debug_utils.DebugUtilsMessengerCallbackData) bool {
 	log.Printf("[%s %s] - %s", severity, msgType, data.Message)
 	return false
 }
 
+func fail(val any) {
+	log.Fatalf("%+v\n", val)
+}
+
 func main() {
 	app := &HelloTriangleApplication{}