Renderer

The renderer handles outputting the screen buffer to the terminal with efficient diff-based rendering and ANSI escape sequence management.

Overview

The renderer provides:

• Diff-based rendering to minimize terminal updates
• ANSI escape sequence generation for styling
• Cursor position optimization
• Cross-platform terminal output

Types

RenderStats

Statistics from a render operation.

Fields

• cells_drawn: usize - Number of cells that were updated
• cells_skipped: usize - Number of cells that remained unchanged
• efficiency: f32 - Rendering efficiency (0.0 to 1.0)

Renderer

Main diff-based renderer for optimal performance.

Fields

• allocator: std.mem.Allocator - Memory allocator
• prev_buffer: ?Screen - Previous frame for diffing
• output_buffer: std.ArrayListUnmanaged(u8) - Buffered output
• current_style: Style - Current terminal style state
• last_x: u16 - Last cursor X position
• last_y: u16 - Last cursor Y position
• stdout: std.fs.File - Standard output handle
• cells_drawn: usize - Statistics: cells drawn this frame
• cells_skipped: usize - Statistics: cells skipped this frame

Methods

init

pub fn init(allocator: std.mem.Allocator) Renderer

Creates a new renderer instance.

Parameters:

• allocator: std.mem.Allocator - Memory allocator

Returns: New Renderer instance

deinit

pub fn deinit(self: *Renderer) void

Cleans up renderer resources.

render

pub fn render(self: *Renderer, current: *const Screen) !void

Renders a screen buffer to the terminal.

Parameters:

• current: *const Screen - Screen buffer to render

Performs diff-based rendering on subsequent calls, full rendering on first call or size changes.

invalidate

pub fn invalidate(self: *Renderer) void

Forces a full redraw on the next render call.

Clears the previous buffer to ensure all cells are re-rendered.

getStats

pub fn getStats(self: *Renderer) RenderStats

Gets rendering statistics from the last frame.

Returns: RenderStats with performance metrics

ImmediateRenderer

Simple immediate-mode renderer without diffing.

Fields

• stdout: std.fs.File - Standard output handle
• current_style: Style - Current style state

Methods

init

pub fn init() ImmediateRenderer

Creates a new immediate renderer.

Returns: New ImmediateRenderer instance

render

pub fn render(self: *ImmediateRenderer, screen_buf: *const Screen) !void

Renders the entire screen buffer immediately.

Parameters:

• screen_buf: *const Screen - Screen buffer to render

Always performs a full redraw of the entire screen.

Usage Examples

Basic Rendering

const allocator = std.heap.page_allocator;
var renderer = Renderer.init(allocator);
defer renderer.deinit();

var screen = try Screen.init(allocator, 80, 24);
defer screen.deinit();

// ... populate screen ...

try renderer.render(&screen);

// Get performance stats
const stats = renderer.getStats();
std.debug.print("Efficiency: {d:.2}%\n", .{stats.efficiency * 100});

Immediate Rendering

var renderer = ImmediateRenderer.init();

// For simple cases or debugging
try renderer.render(&screen);

Forcing Redraw

// When screen content changes significantly
renderer.invalidate();
try renderer.render(&screen); // Will do full redraw

Performance Considerations

• Diff Rendering: The main Renderer only updates changed cells
• Buffering: Output is buffered to minimize syscalls
• Cursor Optimization: Cursor movement is optimized for common patterns
• Style Diffing: Only changed style attributes are sent to terminal

See Also

• Screen API
• Style API
• Source: src/core/renderer.zig