⚓ Harbor — GPU-Accelerated Terminal Emulator

🎯 Goal: build a GPU-driven terminal emulator from scratch with 🦀 Rust + winit + wgpu.

A fast terminal core with a custom wgpu renderer (Vulkan/Metal/DX12), following an Alacritty-like product boundary: GPU-accelerated rendering, strong terminal correctness, minimal built-in UI.

🎨 Custom Renderer

• 📦 Glyph atlas with shelf packing, lazy per-glyph rasterization, incremental texture uploads
• ⚡ Dirty-row incremental updates — pre-allocated vertex buffers, no per-frame full rebuild
• 🧩 Multi-layer compositing in a single render pass: background rects → glyphs → decorations → cursor → scrollbar
• 🌈 Color support: 8/16/256/truecolor fg+bg, Bold / Italic / Underline / Strikethrough / Inverse
• 🖱️ DECSCUSR cursor shapes (block / underline / bar) with blink control
• 🔄 Ring-buffer scrollback (1000-line default) with GPU scrollbar + auto-hide

📊 Current Status

Milestone	Status
🏁 v0.1 End-to-end terminal loop	✅ Windows complete
🧠 v0.2 Terminal core (Parser + SGR + state machine)	🟡 Core done, 317 tests passing 🔬
🖌️ v0.3 Cell-based wgpu renderer	✅ Color / decoration / cursor / viewport done
🚀 v0.4 Interactive features	🟡 Selection (double/triple-click + auto-scroll), clipboard, keyboard mapping done. IME / mouse / paste pending 📜
🎯 v0.5 Performance & stability	🟡 Damage tracking + ring buffer in place

We're well into v0.4 interactive features: multi-click selection (double/triple-click + auto-scroll), clipboard copy/paste, scrollback viewport, and full keyboard with application modes (DECCKM, DECKPAM), Home/End/Page/F1-F12 mappings are done. Next up: IME, mouse protocols, bracketed paste, focus reporting.

cargo run    # 🪟 Windows only — Unix PTY is a stub for now

✨ Features at a Glance

Terminal Core 🧠

• Custom ECMA-48/DEC streaming parser — full state machine covering CSI, OSC, DCS, SOS/PM/APC string families; SGR, DECSTBM, DECSCUSR, alt screen, grid editing (ICH/DCH/IL/DL/SU/SD)
• 317 unit tests covering color modes, scroll regions, cursor save/restore, CJK wide chars, parser error recovery
• CSI parameter hardening — malformed sequences rejected gracefully, unsupported sequences logged via tracing::warn!

GPU Rendering 🎨

• Full render pass: clear → cell backgrounds → glyphs → decorations → cursor → scrollbar
• Each layer owns its pipeline + vertex buffer; incremental uploads via write_buffer
• Font loading with fast-path candidates + fontdb fallback + automatic CJK probe

Scrollback & Scrollbar 📜

• Ring-buffer scrollback (O(1) on full-screen scroll, no cell copies)
• GPU-rendered scrollbar with SDF rounded-rect shader
• Auto-hide after 1500 ms inactivity, proportional thumb height
• Alt-screen isolation — less/vim scrollback stays clean

🏗️ Architecture

winit → App → UiRoot (Background + TextLayer + Decoration + Cursor + Scrollbar)
                ↕
         Terminal → Screen (NormalBuf ring buffer)
                ↕
         Parser (streaming byte-at-a-time)
                ↕
         PTY (Windows ConPTY, Unix stub)

🧪 Run Tests

cargo test   # 317 tests, all passing ✅

⚓ Build a reliable terminal first. Turn it into a development environment later.