Performance

Drawing itself runs entirely on the native side. Touches are never sent to JavaScript, so ink keeps up with the finger even when the JavaScript thread is busy. The costs that remain are in a few specific operations.

While drawing

• iOS: PencilKit renders the ink. There is nothing to tune.
• Android: each touch sample draws one short Bezier segment into an offscreen bitmap, and the screen just copies that bitmap. A long signature costs the same per frame as a short one.

The only JavaScript work during a stroke is the event callbacks: onBegin, onEnd and onChange. Keep them light. In particular, avoid exporting on every onChange; export when the user confirms.

Costly operations

Operation	Why it costs more
Changing penColor or backgroundColor on Android	The bitmap is reallocated and every stroke is redrawn. Changing the pen widths is cheap.
undo() and redo() on Android	The bitmap is cleared and all remaining strokes are redrawn.
undo(), redo(), clear(), setStrokeData() on iOS	The PencilKit canvas is rebuilt so its internal history stays consistent.
replay() on Android	All revealed strokes are redrawn on every frame. Fine for signatures, slower for drawings with thousands of points.
Resizing the view on Android	A new bitmap is allocated at the new size and the strokes are redrawn.

All of these are fast for signature-sized drawings (a few dozen strokes). They only become noticeable if you use the view as a general sketch pad with very large drawings.

Exports

• toBase64() builds a string that is about a third larger than the image and crosses to JavaScript in one piece. For full-screen PNGs on a 3× screen that can be several megabytes. Prefer toFile() and pass the file:// URI to your upload code.
• Use trim: true to export only the signature area. It is usually much smaller than the full canvas.
• Use format: 'jpeg' with a quality around 0.8 when you do not need transparency.
• toSvg() and getStrokeData() are small and fast; they do not render pixels.

Lists

Each SignatureInk owns a native canvas (and on Android a bitmap the size of the view). A few per screen are fine. For long lists:

• Pass removeClippedSubviews={false} to FlatList. Detaching and reattaching native drawing views this way is unreliable, especially on Android.
• Rows that scroll far away are unmounted and lose their drawing. Store each row's stroke data (for example from onEnd with getStrokeData()) and restore it with setStrokeData() when the row mounts again.
• Prefer showing a static image (from toFile()) for rows that are not being edited, and mount the live pad only for the row the user is signing.

See the example app's FlatList screen in the repository for a working version.

Replay

Replay duration grows with the number of points (4 ms each, at least 0.5 s). For a long drawing, pass a higher speed instead of letting the replay run for many seconds.