#!amber
DEVICE_FEATURE sampleRateShading
SHADER vertex vert_shader GLSL
#version 440
layout(location = 0) in vec4 vs_in_position_ndc;
layout(location = 1) in float vs_in_position_screen;
layout(location = 0) out float vs_out_pos_screen;
void main (void)
{
    gl_Position = vs_in_position_ndc;
    vs_out_pos_screen = vs_in_position_screen;
}
END
SHADER fragment frag_shader GLSL
#version 440
layout(location = 0) sample in float fs_in_pos_screen;
layout(location = 0) out vec4 fs_out_color;
void main (void)
{
    const float threshold = 0.0005;
    const float a = interpolateAtSample(fs_in_pos_screen, gl_SampleID);
    const float b = fs_in_pos_screen;
    const bool  valuesEqual = (abs(a - b) < threshold);
    if (valuesEqual)
        fs_out_color = vec4(0.0, 1.0, 0.0, 1.0);
    else
        fs_out_color = vec4(1.0, 0.0, 0.0, 1.0);
}
END
BUFFER position DATA_TYPE vec4<float> DATA
 1.0 -1.0 0.0 1.0
 1.0  1.0 0.0 1.0
-1.0 -1.0 0.0 1.0
-1.0  1.0 0.0 1.0
END
BUFFER position_screen DATA_TYPE float DATA
64.0
64.0
 0.0
 0.0
END
BUFFER framebuffer FORMAT B8G8R8A8_UNORM
PIPELINE graphics pipeline
  ATTACH vert_shader
  ATTACH frag_shader
  VERTEX_DATA position LOCATION 0
  VERTEX_DATA position_screen LOCATION 1
  BIND BUFFER framebuffer AS color LOCATION 0
  FRAMEBUFFER_SIZE 64 64
END
RUN pipeline DRAW_ARRAY AS TRIANGLE_STRIP START_IDX 0 COUNT 4
EXPECT framebuffer IDX 0 0 SIZE 64 64 EQ_RGBA 0 255 0 255