From a7c3ce3a69e6a419a5504c1738b8ee1367cf559b Mon Sep 17 00:00:00 2001
From: David Allemang <david.allemang@kitware.com>
Date: Thu, 21 Mar 2024 13:45:36 -0400
Subject: [PATCH] vulkan-tutorial 04

---
 src/Context.zig | 75 +++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 66 insertions(+), 9 deletions(-)

diff --git a/src/Context.zig b/src/Context.zig
index 68fbc5e..4b9b0a8 100644
--- a/src/Context.zig
+++ b/src/Context.zig
@@ -24,6 +24,7 @@ pub fn init(allocator: std.mem.Allocator) !Self {
     self.allocator = allocator;
 
     self.vkb = try BaseDispatch.load(&c.glfwGetInstanceProcAddress);
+    const vkb = self.vkb;
 
     var exts = std.ArrayList([*:0]const u8).init(allocator);
     defer exts.deinit();
@@ -44,16 +45,16 @@ pub fn init(allocator: std.mem.Allocator) !Self {
     std.log.debug("requesting layers: {s}", .{layers.items});
 
     var available_ext_count: u32 = 0;
-    _ = try self.vkb.enumerateInstanceExtensionProperties(null, &available_ext_count, null);
+    _ = try vkb.enumerateInstanceExtensionProperties(null, &available_ext_count, null);
     const available_exts = try allocator.alloc(vk.ExtensionProperties, available_ext_count);
     defer allocator.free(available_exts);
-    _ = try self.vkb.enumerateInstanceExtensionProperties(null, &available_ext_count, available_exts.ptr);
+    _ = try vkb.enumerateInstanceExtensionProperties(null, &available_ext_count, available_exts.ptr);
 
     var available_layer_count: u32 = 0;
-    _ = try self.vkb.enumerateInstanceLayerProperties(&available_layer_count, null);
+    _ = try vkb.enumerateInstanceLayerProperties(&available_layer_count, null);
     const available_layers = try allocator.alloc(vk.LayerProperties, available_layer_count);
     defer allocator.free(available_layers);
-    _ = try self.vkb.enumerateInstanceLayerProperties(&available_layer_count, available_layers.ptr);
+    _ = try vkb.enumerateInstanceLayerProperties(&available_layer_count, available_layers.ptr);
 
     for (exts.items) |name| {
         const required_name = std.mem.sliceTo(name, 0);
@@ -109,21 +110,73 @@ pub fn init(allocator: std.mem.Allocator) !Self {
         .p_next = if (USE_DEBUG_LAYERS) &debug_create_info else null,
     };
 
-    self.instance = try self.vkb.createInstance(&create_info, null);
-    self.vki = try InstanceDispatch.load(self.instance, self.vkb.dispatch.vkGetInstanceProcAddr);
-    errdefer self.vki.destroyInstance(self.instance, null);
+    self.instance = try vkb.createInstance(&create_info, null);
+    self.vki = try InstanceDispatch.load(self.instance, vkb.dispatch.vkGetInstanceProcAddr);
+    const vki = self.vki;
+    errdefer vki.destroyInstance(self.instance, null);
 
-    if (USE_DEBUG_LAYERS) self.messenger = try self.vki.createDebugUtilsMessengerEXT(
+    if (USE_DEBUG_LAYERS) self.messenger = try vki.createDebugUtilsMessengerEXT(
         self.instance,
         &debug_create_info,
         null,
     );
-    errdefer if (USE_DEBUG_LAYERS) self.vki.destroyDebugUtilsMessengerEXT(
+    errdefer if (USE_DEBUG_LAYERS) vki.destroyDebugUtilsMessengerEXT(
         self.instance,
         self.messenger,
         null,
     );
 
+    var device_count: u32 = 0;
+    _ = try vki.enumeratePhysicalDevices(self.instance, &device_count, null);
+    const devices = try allocator.alloc(vk.PhysicalDevice, device_count);
+    defer allocator.free(devices);
+    _ = try vki.enumeratePhysicalDevices(self.instance, &device_count, devices.ptr);
+
+    // todo some ranking strategy to find the most-suitable device
+    const Selection = struct {
+        device: vk.PhysicalDevice,
+        props: vk.PhysicalDeviceProperties,
+        feats: vk.PhysicalDeviceFeatures,
+    };
+    const selected: Selection = for (devices) |device| {
+        const props = vki.getPhysicalDeviceProperties(device);
+        const feats = vki.getPhysicalDeviceFeatures(device);
+
+        if (props.device_type != vk.PhysicalDeviceType.discrete_gpu) continue;
+
+        // if (feats.geometry_shader == vk.FALSE) continue;
+
+        break .{
+            .device = device,
+            .props = props,
+            .feats = feats,
+        };
+    } else {
+        return error.NoSuitablePhysicalDevice;
+    };
+
+    var queue_family_count: u32 = 0;
+    vki.getPhysicalDeviceQueueFamilyProperties(selected.device, &queue_family_count, null);
+    const queue_family_properties = try allocator.alloc(vk.QueueFamilyProperties, queue_family_count);
+    defer allocator.free(queue_family_properties);
+    vki.getPhysicalDeviceQueueFamilyProperties(selected.device, &queue_family_count, queue_family_properties.ptr);
+
+    var indices = struct {
+        graphics: ?u32 = null,
+    }{};
+
+    for (queue_family_properties, 0..) |prop, idx| {
+        if (indices.graphics == null) {
+            if (prop.queue_flags.graphics_bit) {
+                indices.graphics = @intCast(idx);
+            }
+        }
+
+        if (indices.graphics != null) {
+            break;
+        }
+    }
+
     return self;
 }
 
@@ -203,6 +256,10 @@ const InstanceDispatch = vk.InstanceWrapper(.{
     .createDebugUtilsMessengerEXT = USE_DEBUG_LAYERS,
     .destroyDebugUtilsMessengerEXT = USE_DEBUG_LAYERS,
     .submitDebugUtilsMessageEXT = USE_DEBUG_LAYERS,
+    .enumeratePhysicalDevices = true,
+    .getPhysicalDeviceProperties = true,
+    .getPhysicalDeviceFeatures = true,
+    .getPhysicalDeviceQueueFamilyProperties = true,
 });
 
 const DeviceDispatch = vk.DeviceWrapper(.{});