42 lines
1.6 KiB
Markdown
42 lines
1.6 KiB
Markdown
---
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id: kw-layer
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name: layer
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category: scenes
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kind: keyword
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tokens: layer
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sig: layer Name { handlers }
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tip: A named group of handlers inside a scene; layers render in declaration order.
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order: 1
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---
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A `layer` groups handlers inside a scene, and <b>declaration order is draw order</b>: within a phase the active scene's layers run in the order they were written, so a `Hud` layer declared after a `World` layer paints its `Render` output on top. Layers are the natural unit for stacking a heads-up display over the play-field, or a menu over a paused world. A layer handler may use any phase except `Start` (boot-time setup belongs in the scene's `on enter`). Handlers that should run in every scene are declared outside any scene rather than in a layer.
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```ludic
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program LayerExample {
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property Position { column: int = 0, row: int = 0 }
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model Player { Position }
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let score: int = 0
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scene Overworld start {
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on enter { spawn Player { Position { column: 6, row: 6 } } }
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layer World {
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handler DrawWorld phase Render {
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Screen.clear(Color.MidnightBlue)
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for (current_position) in query [Position, {Player}] {
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Screen.fill_rectangle(x: current_position.column * 16, y: current_position.row * 16, width: 16, height: 16, color: Color.LimeGreen)
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}
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}
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}
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layer Hud {
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handler DrawScore phase Render {
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Screen.draw_text(x: 6, y: 4, text: "SCORE", color: Color.White, scale: 1)
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Screen.draw_number(x: 52, y: 4, value: score, color: Color.Gold, scale: 1)
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Screen.show() # the last layer to draw presents the frame
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}
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}
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}
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}
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```
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