[obiot]

Summary

Camera2d#offset becomes the one field for both a lasting look offset (above the hero, ahead of where he faces) and the shake. It was documented as "offset for shake effect" and only the shake used it: the built-in shake wrote random values into it and zeroed it when done, so any offset a game set was wiped by the next shake.

app.viewport.follow(hero, app.viewport.AXIS.BOTH, 0.1);
app.viewport.offset.set(0, -70); // look a little above the feet

Changes

• Shake: adds its jitter on top of the game's offset and gives that value back exactly when it ends. This also holds when the game changes the offset mid-shake, when the shake is removed or replaced early, or when two shakes run at once (they add up). The bookkeeping stays inside ShakeEffect; there is no new field on the camera.

• Everything that works out what the camera shows now counts the offset:

  • culling (worldView)
  • the pointer (localToWorld, worldToLocal)
  • tile layers, which picked their tiles from the camera position alone and left a strip undrawn under a lasting offset (all render paths: shader, pre-rendered, tile by tile)
  • parallax ImageLayers

  Drawing, lights and fog already counted it.

• reset() clears the offset, so it does not leak from one scene into the next.

• The offset JSDoc is rewritten with an example, and the camera skill gains a section on framing the target off centre.

Behaviour change: parallax backgrounds now shake along with the world, scaled by their ratio. Before, they stood still during a shake. A background with ratio 0 is unaffected. The offset is applied after the camera's bounds, so the view can show past them.

Testing

• tests/camera-offset.spec.js (21 tests). It covers:

  • the shake keeping the offset, including a change mid-shake, early removal, a forced replacement, two stacked shakes, reset() mid-shake and a persistent shake
  • culling and the pointer round trip, with zoom, screen position and roll
  • tile layers drawing the full shifted view, tile by tile and pre-rendered
  • parallax position

  15 deliberately broken versions of the code were all caught.

• The full suite passes (8,788 tests) and pnpm lint passes.

• In the browser, every map of the Tiled map loader example on Canvas, WebGL and WebGPU, at zoom 1, 0.5 and 2: the camera at P with offset O draws the same frame, pixel for pixel, as the camera moved to P + O with no offset. With tile layers blind to the offset (the old code), 10 of the 12 maps had missing tiles.

🤖 Generated with Claude Code

https://claude.ai/code/session_01SeWCkETjW35ZbXDRswV1hx

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