#version 450
#extension GL_EXT_buffer_reference : require

struct Symbol {
  uint x;
  uint top;
  uint width;
};

struct Character {
  uint code;
};

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

layout(buffer_reference, std430) readonly buffer CharacterList{ 
	Character characters[];
};

layout(set = 0, binding = 0) uniform UIUniform {
  mat4 screen;
} ubo;

layout(set = 1, binding = 0) uniform FontUniform {
  uint num_symbols;
  uint width;
  uint height;
  uint space_width;
  SymbolList symbol_list;
  CharacterList characters;
} font;

layout(location = 0) in vec2 inVertexPosition;
layout(location = 1) in vec3 inPosition;
layout(location = 2) in vec2 inSize;
layout(location = 3) in vec4 inColor;
layout(location = 4) in uint code;

layout(location = 0) out vec4 fragColor;
layout(location = 1) out vec2 fragUV;

void main() {
  Symbol symbol = font.symbol_list.symbols[code];
  Character character = font.characters.characters[0];

  float fragU = (inVertexPosition.x*symbol.width + symbol.x) / font.width;
  float fragV = inVertexPosition.y + symbol.top / font.height;
  float x = inVertexPosition.x * inSize.x * symbol.width / font.height;
  float y = (inVertexPosition.y + float(symbol.top)/float(font.height)) * inSize.y;

  fragUV = vec2(fragU, fragV);

  fragColor = inColor;
  gl_Position = ubo.screen * vec4(vec3(x, y, 0.0) + inPosition, 1.0);
}