#version 330 core
layout (location = 0) in vec2 p0;
layout (location = 1) in vec2 p1;
layout (location = 2) in vec4 color;

uniform mat4 projection;

out vec4 fragment_color;

const vec2 rectangle_vertices[4] = vec2[](
    vec2(-1, -1),
    vec2(-1,  1),
    vec2( 1, -1),
    vec2( 1,  1)
);

void main() {
    vec2 dest_half_size = (p1 - p0) / 2;
    vec2 dest_center = (p1 + p0) / 2;
    vec2 dest_position = rectangle_vertices[gl_VertexID] * dest_half_size + dest_center;

    gl_Position = projection * vec4(
        dest_position,
        0,
        1
    );

    fragment_color = color;
}