CustomPaint class

A widget that provides a canvas on which to draw during the paint phase.

When asked to paint, CustomPaint first asks its painter to paint on the current canvas, then it paints its child, and then, after painting its child, it asks its foregroundPainter to paint. The coordinate system of the canvas matches the coordinate system of the CustomPaint object. The painters are expected to paint within a rectangle starting at the origin and encompassing a region of the given size. (If the painters paint outside those bounds, there might be insufficient memory allocated to rasterize the painting commands and the resulting behavior is undefined.) To enforce painting within those bounds, consider wrapping this CustomPaint with a ClipRect widget.

Painters are implemented by subclassing CustomPainter.

Because custom paint calls its painters during paint, you cannot call setState or markNeedsLayout during the callback (the layout for this frame has already happened).

Custom painters normally size themselves to their child. If they do not have a child, they attempt to size themselves to the specified size, which defaults to Size.zero. The parent may enforce constraints on this size.

The isComplex and willChange properties are hints to the compositor's raster cache.

CustomPaint(
  painter: Sky(),
  child: const Center(
    child: Text(
      'Once upon a time...',
      style: TextStyle(
        fontSize: 40.0,
        fontWeight: FontWeight.w900,
        color: Color(0xFFFFFFFF),
      ),
    ),
  ),
)

See also:

• CustomPainter, the class to extend when creating custom painters.
• Canvas, the class that a custom painter uses to paint.