202a631897
Captures the design for replacing BounceMarqueeText with a constant-speed TickerText composable (33 dp/s, continuous leftward scroll with gap looping). Made-with: Cursor
39 lines
1.9 KiB
Markdown
39 lines
1.9 KiB
Markdown
# Ticker Text Design
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## Problem
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The `BounceMarqueeText` composable in `NowPlayingScreen.kt` scrolls long text at a speed proportional to overflow, clamped to 2000–8000ms. For very long titles, the 8000ms cap means the text covers more distance in the same time — making it visibly faster and harder to read. The bounce-back pattern (scroll left, pause, scroll right) also feels unnatural compared to a continuous ticker.
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## Decision
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Replace `BounceMarqueeText` with a `TickerText` composable that scrolls at a constant 33 dp/s leftward, regardless of text length.
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## Design
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### `TickerText` composable
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**Parameters:**
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- `text`, `style`, `color`, `strokeColor`, `strokeWidth`, `modifier` — same as current `BounceMarqueeText`
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- `velocityDpPerSecond: Float = 33f` — constant scroll speed
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**Behavior:**
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- Text fits in container: rendered centered and static (no animation).
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- Text overflows: scrolls continuously leftward at 33 dp/s.
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- After the text exits the left edge, a gap equal to the container width passes (screen appears empty), then the text reappears from the start position and repeats.
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**Animation math:**
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- `totalScrollPx = textWidthPx + containerWidthPx`
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- `durationMs = (totalScrollPx / (velocityDpPerSecond * density)) * 1000`
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- No upper clamp — longer text simply takes longer at the same speed.
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- Keyframes: `0f` → `-(textWidthPx)` with `LinearEasing`, then restart.
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- Initial delay of ~1.5s before first scroll so user can read the beginning.
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**Stroke overlay:** Both the stroke `Text` and fill `Text` remain in the same translated `Box`, moving together.
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**Callers:** `TrackInfoSection` swaps `BounceMarqueeText` → `TickerText` with no other changes.
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## Rejected alternatives
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- **`Modifier.basicMarquee()`** — less control over gap/looping, uncertain Compose BOM version support, harder to keep the stroke overlay working.
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- **Custom `Canvas` + `drawText`** — maximum control but overkill; significantly more code for the same result.
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