Constant VERT_SRC 

const VERT_SRC: &str = "#if NEW_SHADER_INTERFACE\n    #define I in\n    #define O out\n    #define V(x) x\n#else\n    #define I attribute\n    #define O varying\n    #define V(x) vec3(x)\n#endif\n\n#ifdef GL_ES\n    // To avoid weird distortion issues when rendering text etc, we want highp if possible.\n    // But apparently some devices don\'t support it, so we have to check first.\n    #if defined(GL_FRAGMENT_PRECISION_HIGH) && GL_FRAGMENT_PRECISION_HIGH == 1\n        precision highp float;\n    #else\n        precision mediump float;\n    #endif\n#endif\n\nuniform vec2 u_screen_size;\nI vec2 a_pos;\nI vec4 a_srgba; // 0-255 sRGB\nI vec2 a_tc;\nO vec4 v_rgba_in_gamma;\nO vec2 v_tc;\n\nvoid main() {\n    gl_Position = vec4(\n                      2.0 * a_pos.x / u_screen_size.x - 1.0,\n                      1.0 - 2.0 * a_pos.y / u_screen_size.y,\n                      0.0,\n                      1.0);\n    v_rgba_in_gamma = a_srgba / 255.0;\n    v_tc = a_tc;\n}\n";