String vertexShaderSource

Source 

@override
String get vertexShaderSource => """

  uniform mat4 uProjectionMatrix;
  attribute vec2 aVertexPosition;
  attribute vec4 aVertexColor;
  varying vec4 vColor;

  void main() {
    vColor = aVertexColor;
    gl_Position = vec4(aVertexPosition, 0.0, 1.0) * uProjectionMatrix;
  }
  """;