Note: v0.2.21 introduces a new rendering architecture per terminal damage system, and it may contain bugs. Any issue please report 🙏
Changelog
- Breaking:
navigation.use-current-directoryhas been renamed tonavigation.current-working-directory.
Performance Optimizations
- Major: Implemented efficient CVDisplayLink-based VSync synchronization for macOS
- Perfect frame timing aligned with display hardware refresh cycles
- Eliminates screen tearing and stuttering through hardware VSync synchronization
- Adaptive refresh rate support: automatically handles 60Hz, 120Hz, ProMotion displays
- Multi-display support: adapts when windows move between displays with different refresh rates
- Grand Central Dispatch (GCD) integration for thread-safe cross-thread communication
- Smart rendering: Only renders when content actually changes using dirty flag system
- Power efficient: skips unnecessary redraws when content is static, reducing CPU usage
- Professional rendering quality with smooth, tear-free visual updates
- CVDisplayLink runs on dedicated background thread, never blocking UI operations
- macOS VSync Optimization: Disabled redundant software-based vsync calculations on macOS
- CVDisplayLink already provides hardware-synchronized VSync timing
- Eliminates unnecessary frame timing calculations and monitor refresh rate queries
- Reduces CPU overhead and improves rendering performance
- Software vsync logic remains active on other platforms for compatibility
- Major: Implemented a new text run caching system replacing line-based caching
- Up to 96% reduction in text shaping overhead for repeated content
- Individual text runs (words, operators, keywords) cached and reused across frames
- 256-bucket hash table with LRU eviction for optimal memory usage
- Cache Warming: Pre-populate cache with 100+ common terminal patterns on startup
- Programming keywords:
const,let,function,class,import,export, etc. - Indentation patterns: 4/8/12/16 spaces, single/double/triple tabs
- Shell commands:
ls,cd,git,npm,cargo,sudo, etc. - Operators & punctuation:
=,==,=>,();,{},[], etc. - File extensions:
.js,.ts,.rs,.py,.json,.md, etc. - Error/log patterns:
Error:,[INFO],FAILED,SUCCESS, etc. - Immediate cache hits eliminate cold start shaping delays
- Programming keywords:
- SIMD-Optimized Whitespace Detection: Multi-tier optimization for indentation processing
- AVX2: 32 bytes per instruction (x86-64 with AVX2 support)
- SSE2: 16 bytes per instruction (x86-64 with SSE2 support)
- NEON: 16 bytes per instruction (ARM64/aarch64)
- Optimized scalar: 8-byte chunks (universal fallback)
- Up to 32x performance improvement for long indentation sequences
- Critical for Python, nested JavaScript/TypeScript, YAML, and heavily indented code
- Memory Pool for Vertices: High-performance vertex buffer pooling system
- Size-categorized pools: Small (64), Medium (256), Large (1024), XLarge (4096) vertices
- Zero allocation overhead through buffer reuse across frames
- LRU management with automatic cleanup when pools reach capacity
- Thread-safe concurrent access with performance monitoring
- Eliminates GC pressure and improves frame rate consistency
- Background Font Operations: Non-blocking font management
- Font data release and cleanup in dedicated background thread
- System font scanning and preloading without blocking main thread
- Prevents frame rate drops during font operations
- Occlusion-Based Rendering: Skip rendering for occluded windows/tabs
- Automatically detects when windows are completely hidden by other windows
- Skips rendering for occluded windows to save GPU resources and improve performance
- Renders one frame when window becomes visible again to ensure display is updated
- Configurable via
[renderer] disable-occluded-render = true(enabled by default) - Significantly improves performance when running multiple tabs or windows
Other Improvements
- Optimize the character cluster cache for wide space characters.
- New font atlas, more efficient.
- Implemented around 75% Memory Reduction: Text glyphs now use R8 (1 byte) instead of RGBA (4 bytes).
- IME Cursor Positioning: Added configurable IME cursor positioning based on terminal cell coordinates
- IME input popups now appear precisely at the cursor position
- Improves input experience for CJK languages (Chinese, Japanese, Korean)
- Configurable via
[keyboard] ime-cursor-positioning = true(enabled by default)
- Shift+Click Selection: Added Shift+click support for expanding text selections
- Shift+clicking now extends the current selection to the clicked cell
- Provides standard terminal selection behavior expected by users
- Regular clicking without Shift still clears selection and starts new one as before
- CLI accepts relative paths for working directory CLI argument: When invoking rio from other terminals using
rio --working-dir=<path>, a relative path is now correctly processed
Bug Fixes
- Cursor Damage Tracking: Fixed cursor rendering issues after
clearcommand and during rapid typing- Replaced complex point-based damage tracking with simplified line-based approach
- Eliminates edge cases where cursor updates were missed during fast typing sequences
- Improved reliability by always damaging entire lines instead of tracking column ranges
- Aligns with modern terminal design principles for more robust damage calculation
- Selection Rendering: Fixed selection highlight not appearing on first render
- Selection changes now properly trigger damage tracking and rendering
- Optimized selection damage to only redraw affected lines for better performance
- Selection highlights now appear immediately when making selections
- Text Selection: Fixed selection behavior during input and paste operations
- Selection properly clears when typing or pasting text (both bracketed and regular paste)
- Selection coordinates remain stable during viewport scrolling (following Alacritty's approach)
- Prevents selection from being lost unexpectedly during normal terminal usage
- Auto-scroll on Input: Fixed issue where typing after scrolling up wouldn't automatically scroll to bottom
- Now properly scrolls to bottom for both keyboard input and IME/paste operations
- Ensures cursor remains visible when typing new content
- Scroll Performance: Improved scrolling performance by optimizing render event handling
- Moved scroll display offset update before mouse cursor dirty event
- Removed redundant render calls during scroll operations
- Implemented centralized damage-based rendering in event loop for better performance
- macOS IME Improvements: Fixed emoji input and IME stability issues
- Resolved
IMKCFRunLoopWakeUpReliableerrors when using emoji picker - Improved coordinate validation and error handling for IME positioning
- Better handling of direct Unicode input (emoji picker, character viewer)
- Added throttling to prevent excessive IME coordinate updates
- Resolved
- Documentation: Added comprehensive manual pages (man pages) for Unix-like systems
man rio- Main Rio terminal manual page with command-line optionsman 5 rio- Complete configuration file format documentationman 5 rio-bindings- Key bindings reference and customization guide- Available in
extra/man/directory with build instructions
- Terminfo Compatibility: Improved terminal compatibility by adding
xterm-rioterminfo entry- Added
xterm-rioas primary terminfo entry withrioas alias for better application compatibility - Applications that look for "xterm-" prefixed terminals (like termwiz-based apps) now work correctly
- Maintains
TERM=rioenvironment variable for consistency with terminal identity - Fixes crashes with applications like
gituand other termwiz-based terminal programs - Follows same pattern as other modern terminals (Alacritty, Ghostty) for maximum compatibility
- Added
Technical Details
The performance optimizations in this release represent a significant architectural improvement to Rio's text rendering pipeline:
- Text Run Caching: Replaces line-based caching with individual text run caching. Each unique text sequence (word, operator, keyword) is shaped once and reused across all occurrences.
- SIMD Implementation: Platform-adaptive SIMD instructions automatically detect and use the best available CPU features (AVX2 > SSE2 > NEON > optimized scalar) for maximum performance across different architectures.
- Memory Management: The vertex pool system uses size-categorized buffers with LRU eviction, eliminating allocation overhead while preventing memory bloat.
- Cache Strategy: Two-level caching (render data + text runs) with 256-bucket hash table using FxHasher for optimal lookup performance.
- Compatibility: All optimizations maintain full backward compatibility with existing Rio APIs and configurations.
These changes are particularly beneficial for:
- Programming workflows with repetitive code patterns
- Terminal sessions with heavy indentation (Python, nested JS/TS, YAML)
- Long-running sessions where cache warming provides sustained performance benefits
- Systems with limited memory where reduced allocation overhead improves overall responsiveness
Bug Fixes
- Backspace Key Compatibility: Fixed backspace key not working properly in vim when
TERM=xterm-256color- Changed backspace key bindings to send BS (0x08) instead of DEL (0x7F)
- Updated Rio terminfo and termcap entries to match actual key behavior
- Updated XTGETTCAP response to return
^Hforkbscapability - Ensures compatibility with applications expecting xterm-256color backspace behavior
- Fixes issue where vim would display
^?instead of performing backspace operation