#version 450
#extension GL_EXT_buffer_reference : require

struct String {
  vec2 pos;
  vec4 color;
  float size;
  uint code;
};

layout(std430, buffer_reference) readonly buffer StringList {
  String s[];
};

struct Glyph {
  vec2 pos;
  vec4 color;
  float size;
  uint code;
};

layout(std430, buffer_reference) readonly buffer GlyphList {
  Glyph g[];
};

struct Rect {
  vec2 pos;
  vec2 size;
  vec4 color;
};

layout(std430, buffer_reference) readonly buffer RectList {
  Rect r[];
};

layout(std430, buffer_reference) readonly buffer CodeList {
  uint c[];
};

struct DrawCommand {
  uint vertex_count;
  uint instance_count;
  uint fist_vertex;
  uint first_instance;
};

struct DispatchCommand {
  uint x;
  uint y;
  uint z;
};

layout(std430, buffer_reference) buffer UILayer {
  StringList strings;
  CodeList codes;

  RectList rects;
  GlyphList glyphs;

  DrawCommand draw_glyphs;
  DrawCommand draw_rects;

  DispatchCommand dispatch_strings;
};

struct Symbol {
  int top;
  uint left;
  uint width;
  uint height;
  uint advance;
};

layout(std430, buffer_reference) buffer SymbolList {
  Symbol s[];
};


struct Font {
  uint num_symbols;
  uint width;
  uint height;
  SymbolList symbols;
};


layout(std430, buffer_reference) buffer FontList {
  Font f[];
};

layout(std430, buffer_reference) buffer UIContext {
  mat4 screen;
  FontList fonts;
};

layout(std430, push_constant) uniform PushConstant {
  UIContext context;
  UILayer   layer;
} pc;

layout(location = 0) out vec4 fragColor;

const vec2 square[6] = {
  vec2(0.0, 0.0),
  vec2(1.0, 0.0),
  vec2(0.0, 1.0),
  vec2(1.0, 0.0),
  vec2(1.0, 1.0),
  vec2(0.0, 1.0),
};

void main() {
  Rect rect = pc.layer.rects.r[gl_InstanceIndex];
  gl_Position = pc.context.screen * vec4(square[gl_VertexIndex] * rect.size + rect.pos, 0.0, 1.0);
  fragColor = rect.color;
}