#include <metal_stdlib>

using namespace metal;

struct VertexIn {

float value;

};

struct VertexOut {

float4 position [[position]];

float pointSize [[point_size]];

float4 color;

};

struct Uniforms {

uint32_t offset;

uint32_t capacity;

float minValue;

float maxValue;

uint8_t pointSize;

float4 topColor;

float4 bottomColor;

};

vertex VertexOut vertexShader(device VertexIn *vertices [[buffer(0)]],

constant Uniforms *uniforms [[buffer(1)]],

uint vid [[vertex_id]])

{

// normalizedY is in the range [0, 1], where 0 is bottom, 1 is top

float normalizedY = (vertices[vid].value - uniforms->minValue) / (uniforms->maxValue - uniforms->minValue);

// transform normalizedY to the range [-1, 1]

float y = normalizedY * 2.0f - 1.0f;

// Use the offset and the vid to find the index. xIndex is in the range [0, uniforms->numSamples - 1]

float xIndex = float((vid + (uniforms->capacity - uniforms->offset)) % uniforms->capacity);

// Transforming xIndex to the range [-1, 1]

float x = (xIndex / float(uniforms->capacity - 1)) * 2.0f - 1.0f;

VertexOut vOut;

vOut.pointSize = uniforms->pointSize;

vOut.position = {x, y, 1.0f, 1.0f};

vOut.color = mix(uniforms->bottomColor, uniforms->topColor, normalizedY);

return vOut;

}

fragment float4 fragmentShader(VertexOut input [[stage_in]]) {

return input.color;

}