anchor.diff:  /// Defines how a list of points is interpreted when drawing a set of triangles.
   ///
   /// Used by [Canvas.drawVertices].
  +// These enum values must be kept in sync with SkVertices::VertexMode.
   enum VertexMode {
     /// Draw each sequence of three points as the vertices of a triangle.
     triangles,
  
positive.code: ///  * [dart:ui.Gradient], the low-level class used when dealing with the
  ///    [Paint.shader] property directly, with its [new Gradient.linear] and [new
  ///    Gradient.radial] constructors.
  enum TileMode {
    /// Edge is clamped to the final color.
    ///
  
negative.code:   /// ![](https://flutter.github.io/assets-for-api-docs/dart-ui/tile_mode_clamp_linear.png)
    /// ![](https://flutter.github.io/assets-for-api-docs/dart-ui/tile_mode_clamp_radial.png)
    clamp,
  
    /// Edge is repeated from first color to last.
    ///
    /// This is as if the stop points from 0.0 to 1.0 were then repeated from 1.0
    /// to 2.0, 2.0 to 3.0, and so forth (and for linear gradients, similarly from
    /// -1.0 to 0.0, -2.0 to -1.0, etc).
    ///
    /// ![](https://flutter.github.io/assets-for-api-docs/dart-ui/tile_mode_repeated_linear.png)
    /// ![](https://flutter.github.io/assets-for-api-docs/dart-ui/tile_mode_repeated_radial.png)
    repeated,
  
    /// Edge is mirrored from last color to first.
    ///
  