# `GSLayer.TSBFast`

*Instance Property*

Cached top side bearing without updating metrics.

## Declaration

```swift
var tsbFast: CGFloat { get set }
```

```objc
@property (nonatomic, assign) CGFloat TSBFast;
```

```python
TSBFast() -> float
setTSBFast_(TSBFast: float)
```

## Discussion

Use this only when the metrics are already known to be current.

## See Also

### Vertical Metrics

- [`GSLayer.TSB`](/Core/GlyphsCore/GSLayer/TSB) — Distance from the top metric to the top outline edge.
- [`GSLayer TSBPlain`](/Core/GlyphsCore/GSLayer/TSBPlain) — Top side bearing without normalizing the no-outline value.
- [`GSLayer.BSB`](/Core/GlyphsCore/GSLayer/BSB) — Distance from the bottom outline edge to the vertical advance.
- [`GSLayer.BSBFast`](/Core/GlyphsCore/GSLayer/BSBFast) — Cached bottom side bearing without updating metrics.
- [`GSLayer BSBPlain`](/Core/GlyphsCore/GSLayer/BSBPlain) — Bottom side bearing without normalizing the no-outline value.
- [`GSLayer.vertWidth`](/Core/GlyphsCore/GSLayer/vertWidth) — Advance width for vertical text layout.
- [`GSLayer.vertOrigin`](/Core/GlyphsCore/GSLayer/vertOrigin) — Vertical origin offset for vertical text layout.
- [`GSLayer tsbAtHeight:`](/Core/GlyphsCore/GSLayer/tsbAtHeight:) — Top side bearing measured at an x coordinate.
- [`GSLayer setTsb:atHeight:`](/Core/GlyphsCore/GSLayer/setTsb:atHeight:) — Sets the top side bearing measured at an x coordinate.
- [`GSLayer bsbAtHeight:`](/Core/GlyphsCore/GSLayer/bsbAtHeight:) — Bottom side bearing measured at an x coordinate.
- [`GSLayer setBsb:atHeight:`](/Core/GlyphsCore/GSLayer/setBsb:atHeight:) — Sets the bottom side bearing measured at an x coordinate.