Implement diff-based rendering to eliminate screen flickering#61
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Add double-buffering terminal wrapper that renders to a pending buffer and only outputs changed cells on flush, eliminating the visual flicker caused by unconditional screen clears on every render cycle. New components: - TerminalCell: Value type representing a single cell with character, colors, and text decoration - FrameBuffer: 2D buffer of TerminalCell with efficient diffing via GetChangedRuns() that groups consecutive changes for minimal cursor movement - DiffingTerminal: IAnsiTerminal wrapper that intercepts all rendering calls, maintains current/pending frame buffers, and emits only changed cells Key behavior changes: - ClearScreen() now only clears the pending buffer, not the actual terminal - Flush() diffs pending vs current buffer and outputs only differences - ForceFullRefresh() forces complete redraw (used on resize or corruption) - TerminaApplication auto-wraps terminals with DiffingTerminal (except VirtualTerminal for testing) This is the same proven pattern used by ncurses, termbox, and other TUI libraries to achieve flicker-free rendering.
Remove SetCursorVisible calls from FlushFull and FlushDiff methods that were incorrectly toggling cursor visibility on every render. The application should control cursor visibility, not the terminal wrapper. This fixes a regression where multiple cursors would appear in the UI because the flush methods were unconditionally showing the cursor after each render cycle.
Skip resize when terminal reports zero width or height, which occurs in headless CI environments. This prevents ArgumentOutOfRangeException when FrameBuffer.Resize is called with invalid dimensions.
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Summary
DiffingTerminal) that renders to a pending buffer and only outputs changed cells on flushChanges
New components:
TerminalCell- Value type representing a single cell with character, colors, and text decorationFrameBuffer- 2D buffer with efficient diffing viaGetChangedRuns()that groups consecutive changes for minimal cursor movementDiffingTerminal-IAnsiTerminalwrapper that intercepts all rendering calls and emits only changed cellsKey behavior:
ClearScreen()now only clears the pending buffer, not the actual terminalFlush()diffs pending vs current buffer and outputs only differencesForceFullRefresh()forces complete redraw (used on resize)TerminaApplicationauto-wraps terminals withDiffingTerminalTest plan
FrameBuffer(14 tests)DiffingTerminal(21 tests)