A Vertex shader that mirrors its source horizontally

Mirror Vector Shader

  private static final String FRAGMENT_SHADER_MIRROR =
          "#extension GL_OES_EGL_image_external : require\n" +
                  "precision mediump float;\n" +
                  "varying vec2 vTextureCoord;\n" +           // Coordinate within texture
                  "uniform samplerExternalOES sTexture;\n" +  // Texture
                  "uniform vec2 uPosition;\n" +               // Position within OpenGL scene
                  "void main() {\n" +
                  "    vec2 texCoord = vTextureCoord.xy;\n" +
                  "    vec2 normCoord = 2.0 * texCoord - 1.0;\n"+
                  "    normCoord.x = normCoord.x * sign(normCoord.x + uPosition.x);\n"+
                  "    texCoord = normCoord / 2.0 + 0.5;\n"+
                  "    gl_FragColor = texture2D(sTexture, texCoord);\n"+
                  "}\n";