55 lines
1.9 KiB
Markdown
55 lines
1.9 KiB
Markdown
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# VulkanAnimated
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A live HUD demo: three `Observable<float>`s drive `ProgressBar`s, three
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`Observable<std::string>`s drive `Text` labels, and an FPS readout in
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the corner ticks every frame. Everything updates from a single
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`onUpdate` listener — no `Invalidate()` / `Redraw()` calls.
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## What it shows
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- **`Observable<T>` data flow**: change a value in `onUpdate`, the
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next frame's `RebuildFrame` re-emits the draw list with the new value
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automatically. No tree rebuild.
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- **`ProgressBar::bindValue(obs, lo, hi)`** — the bar fill normalises the
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observable's current value into 0..1 each frame.
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- **`Text::bind(observable)`** — the displayed string is sourced from
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the observable each frame, replacing any baked-in runs.
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- **Composition pattern**: a small lambda helper builds one HP/MP-style
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row (`Text` + `ProgressBar` inside an `HStack`) given the observables
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and a colour, then the row is dropped into the parent `VStack` like
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any other widget.
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- **Different update rates per observable**: `health` oscillates at 0.7
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rad/s, `mana` at 1.3, `charge` advances linearly modulo 1 — visible
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proof that each observable updates independently.
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## Run
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```bash
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cd examples/VulkanAnimated
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crafter-build -r
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```
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You should see "Animated HUD" with three coloured bars (red HP, blue MP,
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yellow Charge) all moving at different rates, with the FPS readout in
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the top-right ticking once per frame.
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Click `Quit` to exit.
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## Notes
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The whole tick handler is just:
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```cpp
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EventListener<FrameTime> tick(&window.onUpdate, [&](FrameTime ft){
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t += ft.delta.count();
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health = 0.5f + 0.5f * std::sin(t * 0.7f);
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mana = std::abs(std::sin(t * 1.3f));
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charge = std::fmod(t * 0.3f, 1.0f);
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healthLabel = std::format("HP {:>3.0f} / 100", health.Get() * 100);
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// …
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});
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```
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That's the entire animation system. There is deliberately no
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`Animation<T>` / tween primitive in the library — drive observables
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from any source you like.
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