29 lines
1.8 KiB
Markdown
29 lines
1.8 KiB
Markdown
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# Proposal
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## Why
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The render loop repaints the full canvas on every frame callback (~60 fps) even though the simulation ticks at only 20 tps and starts paused, so most frames draw an identical image. This keeps CPU usage at ~85% during idle, dominated by the full-canvas clear and the full grid scan.
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## What Changes
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- Split simulation timing out of `redraw()`; ticks are driven by the event loop, not by the render call.
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- Render a frame only when displayed content can have changed: a simulation tick, cell edit or pattern placement, pattern preview movement (pointer motion, tool selection, rotation), grid-line toggle, or canvas resize.
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- When nothing changed, commit an empty frame (frame callback without attaching a new buffer), so the idle loop costs nearly nothing.
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- Draw incrementally: keep a snapshot of the grid as last rendered, diff it per row against the current grid, and repaint only changed cells (background, grid-line fragments, cell) instead of clearing the whole canvas.
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- Report damage for the changed region instead of the whole surface.
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- Full-canvas repaint remains for resize, grid-line toggle, and when the diff covers most of the grid.
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## Capabilities
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### New Capabilities
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- `on-demand-rendering`: Scheduling of window repaints — when a frame is produced (only on content change) and how changed cells are drawn incrementally.
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### Modified Capabilities
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## Impact
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- `wlgol.c`: render loop (`redraw`, `wl_callack_done`, `main` dispatch loop), simulation tick timing, buffer commit/damage logic.
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- `include/grid.h` / `grid.c`: possible helper for snapshotting the grid (no behavioral change to existing grid functions).
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- No protocol, dependency, or configuration changes. Rendering output is visually identical to the current renderer; only the frequency and extent of repainting change.
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