feat(graphics): add double buffering with dirty region tracking #97
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Implement Phase 1 of the graphics stack roadmap with double buffering support for the interactive shell framebuffer. Architecture: - DoubleBufferedFrameBuffer: heap-allocated shadow buffer with flush() - ShellFrameBuffer: Option<DoubleBufferedFrameBuffer> for lazy upgrade - Direct writes during early boot (before heap), double-buffered after Key features: - Shadow buffer allocated after heap init via upgrade_to_double_buffer() - Batched writes with dirty tracking for efficient flushing - Safe slice operations for shadow buffer, unsafe only for hardware copy - Zero warnings, no #[allow(dead_code)] annotations Files: - kernel/src/graphics/mod.rs - new graphics module - kernel/src/graphics/double_buffer.rs - DoubleBufferedFrameBuffer impl - kernel/src/logger.rs - ShellFrameBuffer with optional double buffering - kernel/src/main.rs - upgrade call after memory::init() Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Phase 2 of graphics stack: Enhanced framebuffer features - Add DirtyRegion struct for tracking modified rectangular areas - Implement partial flush that only copies dirty scanline regions - Add scroll_hardware_up for optimized scroll operations - Track modifications at pixel granularity in write_pixel - Reduce memory bandwidth by avoiding full buffer copies Performance improvement: Only flushing changed regions instead of the entire framebuffer (4MB at 1080p) on every character write. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Fixes issues identified by technical validation:
1. Fix coordinate bug in write_pixel dirty region marking:
- Changed from absolute buffer offset to within-scanline byte offset
- mark_region_dirty now receives x_byte_offset (x * bytes_per_pixel)
instead of byte_offset (which included row offset)
2. Add unit tests for DirtyRegion:
- dirty_region_new_is_empty: verifies new() creates empty region
- dirty_region_mark_expands: verifies mark_dirty sets correct bounds
- dirty_region_mark_unions: verifies multiple marks union correctly
- dirty_region_clear_resets: verifies clear() resets to empty
3. Add unit tests for DoubleBufferedFrameBuffer:
- double_buffer_new_not_dirty: verifies initial state
- double_buffer_mark_region_sets_dirty: verifies marking works
- double_buffer_flush_clears_dirty: verifies flush resets state
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Adds 5 tests to verify the core dirty region tracking behavior: 1. double_buffer_flush_copies_dirty_bytes - Verifies flush() actually copies bytes from shadow to hardware 2. double_buffer_flush_only_copies_dirty_region - Verifies non-dirty regions are NOT touched (partial flush works) 3. double_buffer_flush_full_copies_everything - Verifies flush_full() copies entire buffer regardless of dirty state 4. double_buffer_coordinate_interpretation - Guards against regression of x_byte_offset bug - Verifies x coordinates are within-row offsets, not absolute 5. double_buffer_scroll_hardware_up - Tests hardware buffer scroll operation These tests address validation feedback that the previous tests only verified state management but not the actual optimization behavior. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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Summary
Implements Phase 1 and Phase 2 of the graphics stack for tear-free shell rendering:
flush()copies to hardware.scroll_hardware_up()shifts hardware buffer directly for efficient scrolling.Test plan
interactiveandtestingfeatures)Changes
kernel/src/graphics/mod.rskernel/src/graphics/double_buffer.rskernel/src/logger.rskernel/src/lib.rskernel/src/main.rs🤖 Generated with Claude Code