starting to test swapchain

src/au/SwapChain.zig

@@ -0,0 +1,68 @@
+const std = @import("std");
+const au = @import("../au.zig");
+const vk = @import("vk");
+
+const Self = @This();
+
+alloc: std.mem.Allocator,
+cinfo: vk.SwapchainCreateInfoKHR,
+handle: vk.SwapchainKHR,
+
+pub fn init(alloc: std.mem.Allocator) !Self {
+    const caps = try au.I.getPhysicalDeviceSurfaceCapabilitiesKHR(au.device_config.pdev, au.W.surface);
+
+    var min_image_count = @max(3, caps.min_image_count + 1); // todo magic numbers
+    if (caps.max_image_count > 0) {
+        min_image_count = @min(min_image_count, caps.max_image_count);
+    }
+
+    // determine format
+    const format = au.device_config.format;
+
+    return .{
+        .alloc = alloc,
+        .cinfo = .{
+            .surface = au.W.surface,
+            .min_image_count = min_image_count,
+            .image_format = format.format,
+            .image_color_space = format.color_space,
+            .image_extent = undefined, // set in rebuild
+            .image_array_layers = 1,
+            .image_usage = .{ .color_attachment_bit = true },
+            .image_sharing_mode = .exclusive,
+            .pre_transform = .{ .identity_bit_khr = true },
+            .composite_alpha = .{ .opaque_bit_khr = true },
+            .present_mode = au.device_config.mode,
+            .clipped = vk.TRUE,
+            .old_swapchain = .null_handle,
+        },
+        .handle = .null_handle,
+    };
+}
+
+pub fn deinit(self: *Self) void {
+    au.D.destroySwapchainKHR(self.handle, null);
+}
+
+/// mark that the swapchain _should_ be rebuilt with the given extent
+/// this function is reentrant, so the swapchain can be marked multiple times
+/// and only one rebuild occur
+pub fn mark(self: *Self) void {
+    self.handle = .null_handle;
+}
+
+/// rebuild the swapchain only if it is marked. return true if the swapchain was rebuilt.
+pub fn rebuild(self: *Self) !bool {
+    if (self.handle != .null_handle) return false;
+
+    const caps = try au.I.getPhysicalDeviceSurfaceCapabilitiesKHR(au.device_config.pdev, self.cinfo.surface);
+    self.cinfo.image_extent = caps.current_extent;
+
+    self.handle = try au.D.createSwapchainKHR(&self.cinfo, null);
+    au.D.destroySwapchainKHR(self.cinfo.old_swapchain, null);
+    self.cinfo.old_swapchain = self.handle;
+
+    // todo repopulate images and synchronization
+
+    return true;
+}