35 lines
1.4 KiB
Markdown
35 lines
1.4 KiB
Markdown
# ADR 0001: LCD Expression and Presentation Ownership
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## Status
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Accepted
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## Context
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LCD behavior now needs multiple reusable expressions that can be triggered by
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different runtime conditions. The system must keep semantic expression ownership
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separate from low-level LCD playback so future expressions can be added without
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copying cross-layer contracts or coupling orchestration code to asset paths.
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## Decision
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- `domain` owns LCD expression semantics and declares `domain_expression_*` in
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`components/domain/include/domain.h`.
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- `control_plane` owns trigger policy: it decides when a runtime condition
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requests a semantic expression.
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- `platform` owns LCD presentation playback primitives and declares
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`platform_lcd_presentation_*` in `components/platform/include/platform.h`.
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- Domain runtime adapters map semantic expressions to platform presentation
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requests.
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- Platform LCD internals serialize presentation requests and perform all panel
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drawing inside the LCD render task.
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## Consequences
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- Adding a new expression requires a domain expression ID and catalog mapping,
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plus an optional control-plane trigger rule.
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- Public upper-layer facades must not expose platform playback types.
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- Platform public APIs must not expose domain semantic expression IDs.
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- High-priority expressions can interrupt lower-priority presentations without
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leaking policy logic into the LCD driver.
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