/// <summary>
/// Draws a rectangle representing a single color key in the gradient.
/// </summary>
/// <param name="color">Color to display.</param>
/// <param name="t">Time at which to draw the rectangle, in range [0, 1].</param>
/// <param name="selected">True to draw the rectangle as selected, plain otherwise.</param>
private void DrawColor(Color color, float t, bool selected)
{
int x = TimeToPixel(t);
Vector2I a = new Vector2I(x + RECT_WIDTH / 2, 0);
Vector2I b = new Vector2I(x + RECT_WIDTH / 2, height - 1);
Vector2I c = new Vector2I(x - RECT_WIDTH / 2, 0);
Vector2I d = new Vector2I(x - RECT_WIDTH / 2, height - 1);
Vector2I[] linePoints = new Vector2I[] { a, b, d, c, a };
Vector2I[] trianglePoints = new Vector2I[] { a, b, c, d };
Color colorNoAlpha = color;
colorNoAlpha.a = 1.0f;
canvas.DrawTriangleStrip(trianglePoints, colorNoAlpha, 102);
canvas.DrawPolyLine(linePoints, selected ? SELECTED_COLOR : PLAIN_COLOR, 100);
Vector2I alphaA = new Vector2I(x - 1, height - 1);
Vector2I alphaB = new Vector2I(x + RECT_WIDTH / 2, height / 2);
Vector2I alphaC = new Vector2I(x + RECT_WIDTH / 2, height - 1);
canvas.DrawTriangleList(new [] { alphaA, alphaB, alphaC }, Color.White * color.a, 101);
}