MutableRectangle<T extends num> constructor

Create a mutable rectangle spanned by (left, top) and (left+width, top+height).

The rectangle contains the points with x-coordinate between left and left + width, and with y-coordinate between top and top + height, both inclusive.

The width and height should be non-negative. If width or height are negative, they are clamped to zero.

If width and height are zero, the "rectangle" comprises only the single point (left, top).

Example:

var rectangle = MutableRectangle(20, 50, 300, 600);
print(rectangle); // Rectangle (20, 50) 300 x 600
print(rectangle.left); // 20
print(rectangle.top); // 50
print(rectangle.right); // 320
print(rectangle.bottom); // 650

// Change rectangle width and height.
rectangle.width = 200;
rectangle.height = 100;

print(rectangle); // Rectangle (20, 50) 200 x 100
print(rectangle.left); // 20
print(rectangle.top); // 50
print(rectangle.right); // 220
print(rectangle.bottom); // 150