Implement flair-ui: complete Vulkan-backed 2D vector graphics library in Zig

[Copilot]

• Explore codebase and understand all files needing changes
• Create src/c_headers/vulkan.h wrapper header
• Create src/c_headers/wayland.h wrapper header
• Update build.zig — add b.addTranslateC() steps for both headers and wire modules into the library
• Update src/vulkan.zig — replace @cImport with @import("vulkan_c")
• Update src/platform/wayland.zig — replace @cImport with @import("wayland_c")
• Update src/image.zig — replace removed std.compress.zlib with a manual DEFLATE-stored / zlib encoder
• Update build.zig.zon — bump minimum_zig_version to "0.16.0"

Original prompt

Overview

Implement a complete 2D vector graphics library in Zig that depends exclusively on Vulkan for rendering. The library is called flair-ui and should provide a clean, ergonomic public API.

Core Concepts

1. Surface — The Central Drawing Primitive

A Surface is the primary thing users draw onto. It is backed by a Vulkan image/framebuffer.

• A surface has a width, height, and pixel format (RGBA8).
• All drawing operations target a surface.
• A surface can be saved to disk as an image (PNG format — use a pure-Zig PNG encoder or a minimal stb_image_write binding).
• A surface can be presented to a window (see below).

2. Drawing Primitives / Shapes

The library must support drawing the following shapes. Every shape can be drawn as either filled or as stroked (outline) with a configurable stroke width:

1. Line — from point A to point B, with configurable width.
2. Path — a sequence of connected line segments (polyline). Can be open or closed.
3. Bézier curves — quadratic and cubic Bézier curves, defined by control points.
4. Circle — defined by center + radius.
5. Circular arc — a portion of a circle, defined by center, radius, start angle, end angle.
6. Oval (Ellipse) — defined by center + x-radius + y-radius.
7. Oval arc (Elliptical arc) — a portion of an ellipse.
8. Rectangle — defined by position + size, with an optional corner radius for each corner independently (to support rounded rects, pill shapes, etc.).

3. Color & Paint System

• Colors are RGBA (f32 components, 0.0–1.0).
• A Paint type represents how a shape is filled/stroked:
  • Solid color
  • Linear gradient — defined by two points + array of color stops
  • Radial gradient — defined by center, radius + array of color stops
• Paint is passed as a parameter to every draw call.

4. Draw Style

Every shape draw function accepts a DrawStyle:

• .fill — fill the interior
• .stroke with a configurable line_width

5. Window — Platform-Agnostic Abstraction

A Window presents a surface to the screen and handles input.

• The Window interface/API must be platform-agnostic so it can later be ported to macOS (Metal/Cocoa) and Windows (Win32).
• Use a vtable or tagged-union pattern in Zig for the platform backend.
• For now, implement only the Wayland backend:
  • Use libwayland-client via Zig's @cImport / C interop.
  • Use xdg-shell for window decoration/toplevel.
  • Present the Vulkan surface to the Wayland surface via VK_KHR_wayland_surface.
• The window should support:
  • Creating/destroying a window with a title and size.
  • Resizing.
  • Closing.
  • An event loop (pollEvents() or similar).

6. Input Handling

The window must handle user input and expose it through an event system:

• Keyboard events: key press, key release, key repeat. Include the key code/scancode and modifier state (shift, ctrl, alt, super).
• Mouse events:
  • Mouse button press/release (left, right, middle, etc.)
  • Mouse move (position)
  • Mouse scroll (vertical and horizontal)
  • Mouse enter/leave the window
• Events should be delivered through a polling model: the user calls something like window.pollEvents() which returns an iterator/slice of events, or the user registers callback functions.
• For Wayland, keyboard input comes from wl_keyboard and mouse from wl_pointer via the wl_seat interface.

Architecture & File Structure

flair-ui/
├── build.zig                  # Build script: compile shaders (GLSL→SPIR-V), link Vulkan, link wayland
├── build.zig.zon              # Package manifest
├── src/
│   ├── root.zig               # Public API — re-exports everything users need
│   ├── surface.zig            # Surface type, create/destroy, save-to-image
│   ├── renderer.zig           # Vulkan initialization, pipeline management, draw command submission
│   ├── vulkan.zig             # Vulkan helpers: instance, device, swapchain, memory, etc.
│   ├── shapes.zig             # Shape tessellation: convert shapes → triangle vertices on CPU
│   ├── color.zig              # Color, Gradient, ColorStop, Paint types
│   ├── image.zig              # PNG encoding / image export
│   ├── window.zig             # Platform-agnostic Window interface (vtable pattern)
│   ├── input.zig              # Event types: KeyEvent, MouseButtonEvent, MouseMoveEvent, ScrollEvent
│   ├── platform/
│   │   └── wayland.zig        # Wayland backend: wl_display, xdg_shell, wl_seat, wl_keyboard, wl_pointer
│   └── shaders/
│       ├── fill.vert.glsl     # Vertex shader — passes position + UV + color to fragment
│       └── fill.frag.glsl     # Fragment shader — handles solid color and gradient interpolation
├── examples/
│   ├── basic_shapes.zig       # Example: draw all shape types to a surface, save as PNG
│   └── window_events.zig      # Example: open a window, draw shapes, handle mouse/keyboard
└── README.md                  # Documenta...

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