Gradient.radial constructor
Creates a radial gradient centered at center
that ends at radius
distance from the center.
If colorStops
is provided, colorStops[i]
is a number from 0.0 to 1.0
that specifies where color[i]
begins in the gradient. If colorStops
is
not provided, then only two stops, at 0.0 and 1.0, are implied (and
color
must therefore only have two entries). Stop values less than 0.0
will be rounded up to 0.0 and stop values greater than 1.0 will be rounded
down to 1.0. Each stop value must be greater than or equal to the previous
stop value. Stop values that do not meet this criteria will be rounded up
to the previous stop value.
The behavior before and after the radius is described by the tileMode
argument. For details, see the TileMode enum.
If center
, radius
, colors
, or tileMode
are null, or if colors
or
colorStops
contain null values, this constructor will throw a
NoSuchMethodError.
If matrix4
is provided, the gradient fill will be transformed by the
specified 4x4 matrix relative to the local coordinate system. matrix4
must
be a column-major matrix packed into a list of 16 values.
If focal
is provided and not equal to center
and focalRadius
is
provided and not equal to 0.0, the generated shader will be a two point
conical radial gradient, with focal
being the center of the focal
circle and focalRadius
being the radius of that circle. If focal
is
provided and not equal to center
, at least one of the two offsets must
not be equal to Offset.zero.
Implementation
Gradient.radial(
Offset center,
double radius,
List<Color> colors, [
List<double>? colorStops,
TileMode tileMode = TileMode.clamp,
Float64List? matrix4,
Offset? focal,
double focalRadius = 0.0
]) : assert(_offsetIsValid(center)),
assert(matrix4 == null || _matrix4IsValid(matrix4)),
super._() {
_validateColorStops(colors, colorStops);
final Int32List colorsBuffer = _encodeColorList(colors);
final Float32List? colorStopsBuffer = colorStops == null ? null : Float32List.fromList(colorStops);
// If focal is null or focal radius is null, this should be treated as a regular radial gradient
// If focal == center and the focal radius is 0.0, it's still a regular radial gradient
if (focal == null || (focal == center && focalRadius == 0.0)) {
_constructor();
_initRadial(center.dx, center.dy, radius, colorsBuffer, colorStopsBuffer, tileMode.index, matrix4);
} else {
assert(center != Offset.zero || focal != Offset.zero); // will result in exception(s) in Skia side
_constructor();
_initConical(focal.dx, focal.dy, focalRadius, center.dx, center.dy, radius, colorsBuffer, colorStopsBuffer, tileMode.index, matrix4);
}
}