<VertexShader>

attribute mediump vec3  aPosition;
attribute mediump vec2  aTexCoord;

uniform   mediump mat4  uMvpMatrix;
uniform   lowp    vec4  uColor;
uniform   lowp    vec4  uTextColor;
uniform   lowp    vec4  uGradientColor;
uniform   mediump vec4  uGradientLine;
uniform   mediump vec2  uInvTextSize;

varying   mediump vec2  vTexCoord;
varying   lowp    vec4  vColor;

void main()
{
  gl_Position = uMvpMatrix * vec4(aPosition, 1.0);
  vTexCoord = aTexCoord;

  lowp float f = dot( aPosition.xy * uInvTextSize - uGradientLine.xy, uGradientLine.zw );

  vColor = mix(uTextColor, uGradientColor, f);
}

</VertexShader>

<FragmentShader>

uniform mediump sampler2D sTexture;
uniform lowp    vec4      uColor;
uniform highp   vec2      uSmoothing;
uniform highp   vec2      uOutline;
uniform lowp    vec4      uOutlineColor;
uniform highp   float     uGlow;
uniform lowp    vec4      uGlowColor;

varying mediump vec2      vTexCoord;
varying lowp vec4         vColor;

void main()
{
  // sample distance field
  mediump float distance = texture2D(sTexture, vTexCoord).a;

  // blend fragment color between outline color and text color
  mediump float outlineBlend = smoothstep(uOutline[0], uOutline[1], distance);

  lowp vec4 clampedColor = clamp( vColor, 0.0, 1.0 );

  // create blend between text color and outline color using outlineBlend
  lowp vec4 outlineColor = vec4( uOutlineColor.rgb, uOutlineColor.a * clampedColor.a );
  lowp vec4 color = mix(outlineColor, clampedColor, outlineBlend);

  mediump float glowBlend = smoothstep(uSmoothing[0], uSmoothing[1], distance);

  // blend fragment color between glow color and text color
  lowp vec4 glowColor = vec4( uGlowColor.rgb, uGlowColor.a * clampedColor.a );
  color = mix(glowColor, color, glowBlend);

  // fade out glow between uSmoothing and uGlow
  color.a *= smoothstep(uGlow, uSmoothing[0], distance);

  // final color multiplied by Actor color
  gl_FragColor = uColor * color;
}

</FragmentShader>