UI groundwork

The UI library is staged under ui/ until it moves into the standard library as std/ui.

• ui/protocols holds the Wayland protocol XML the library is built from: wayland.xml and xdg-shell.xml.
• go run ./cmd/wlgen -o wayland.low ui/protocols/wayland.xml ui/protocols/xdg-shell.xml generates Low bindings for libwayland-client.
  • Every interface given in one run shares an Interfaces record of wl_interface tables that interfaces() builds in C memory. A reference to an interface that no given protocol declares is an error.
  • A request becomes interface_request(...) over wl_proxy_marshal_flags, taking the Interfaces record when it creates an object of a known interface. wl_registry_bind takes the interface table and version.
  • Destructor requests pass WL_MARSHAL_FLAG_DESTROY, and an interface without a destroy request gets one that calls wl_proxy_destroy.
  • Objects are ptr, strings ptr[u8], fixed an i32.
  • Events become an extern struct listener of extern fn fields, each defaulting to a generated function that ignores the event, so a listener names only the events it handles. interface_add_listener copies it into C memory. Callbacks receive the listener's data pointer, usually a pinned Low object.
  • Enum entries are functions such as wl_shm_format_argb8888() -> u32. Names that clash with Low keywords or builtins gain a trailing _.
• ui/shaders holds GLSL for instanced quads with per-corner radii, borders and clipping, blurred shadows, and monochrome glyph sprites sampled from an R8 atlas. Instances are read from a storage buffer at set 0 binding 0 and the viewport size is a push constant. go run ./cmd/shadergen ui/shaders compiles each stage with glslc to a checked-in .spv and records the sources' SHA-256 sums in sources.sum.
• ui/registry holds the Vulkan registry, vk.xml.gz from Vulkan-Docs v1.4.363, and vulkan.list, which selects extensions, commands and extra types such as pNext structures.
  • go run ./cmd/vkgen -registry ui/registry/vk.xml.gz -select ui/registry/vulkan.list -o vulkan.low generates Low bindings for the selected commands and every type they reach, skipping Vulkan SC variants. Enum values come from the core enums, every Vulkan feature level and the selected extensions.
  • A handle is a one-field extern struct, ptr for dispatchable handles and i64 for the others, so VkBuffer {} is the null handle and handles of different kinds do not mix.
  • Structures and unions become extern structs whose fields all have defaults: zero, null, the empty handle, or for sType the structure's own value, so a literal names only what it sets. A union takes the layout of its widest member.
  • A fixed C array becomes numbered fields, name_0 to name_N, with an accessor Struct_name(s) that returns them as a slice, or as a str for a character array.
  • Vulkan types map to u32 (uint32_t, VkBool32, VkFlags, 32-bit flag bits), i32 (int32_t, enums), i64 (uint64_t, VkDeviceSize, VkFlags64, size_t), u16, u8, f32 and f64.
  • Pointers to known types become ptr[T]; void*, function pointers and pointers to pointers become ptr. A command's single input or output through a pointer is a mut parameter; an array or optional pointer is a ptr[T].
  • Enum entries and API constants are functions such as VK_FORMAT_R8G8B8A8_UNORM() -> i32, and vk_make_api_version builds version numbers.