funfriend/src/buddy_renderer.cr

class Funfriend::BuddyRenderer
  getter buddy : Buddy

  getter buddy_shader : Program
  getter bg_shader : Program
  getter vertex_array : VertexArray
  getter vertex_buffer : Buffer
  getter textures : TextureMan::TextureBasket
  getter bg_texture : Texture?

  def initialize(@buddy : Buddy)
    @buddy_shader, @bg_shader = init_shaders
    @vertex_array, @vertex_buffer = init_buffers
    @textures = buddy.textures
    @bg_texture = buddy.bg_texture
  end

  def funfriend_size
    funfriend_size = ConfigMan.config["window"]["funfriend_size"].as(Int32)
    {width: funfriend_size, height: funfriend_size}
  end

  def init_buffers
    vertices = {
      # ------ positions -------    texture coordinates
      1.0f32,   1.0f32,   0.0f32,   1.0f32,   1.0f32, # top right
      1.0f32,  -1.0f32,   0.0f32,   1.0f32,   0.0f32, # bottom right
     -1.0f32,  -1.0f32,   0.0f32,   0.0f32,   0.0f32, # bottom left
     -1.0f32,   1.0f32,   0.0f32,   0.0f32,   1.0f32  # top left
    }

    # Indices used for indexed draw calls. Each is used as an index into the four vertices.
    indices = {
      0, 1, 3,  # first triangle
      1, 2, 3   # second triangle
    }

    vertex_buffer = Buffer.new
    element_buffer = Buffer.new
    vertex_array  = VertexArray.new

    vertex_array.bind do
      vertex_buffer.bind(Buffer::Target::Array) do |buffer, target|
        target.buffer_data(vertices, Buffer::UsageHint::StaticDraw)
        vertex_array.define_attributes do |va|
          va.attribute(3, DataType::Float, false)
          va.attribute(2, DataType::Float, false)
        end
      end

      # bind the element buffer to GL_ELEMENT_ARRAY_BUFFER
      element_buffer.bind(Buffer::Target::ElementArray)

      # Send index data to the GPU.
      Buffer::Target::ElementArray.buffer_data(indices, Buffer::UsageHint::StaticDraw)
    end

    # unbind the element buffer.
    element_buffer.unbind

    return {vertex_array, vertex_buffer}
  end

  def init_shaders
    {GL.shader("funfriend.frag", "nop.vert"), GL.shader("nop.frag", "nop.vert")}
  end

  def render(dt : Float64, window_width : Int32, window_height : Int32)
    LibGL.clear_color(0.0, 0.0, 0.0, 0.0)
    LibGL.clear(Buffer::Bit::Color)

    textures.update(dt)
    frame = textures.texture

    width, height = frame[:width], frame[:height]

    LibGL.enable(LibGL::BLEND)
    LibGL.blend_func(LibGL::SRC_ALPHA, LibGL::ONE_MINUS_SRC_ALPHA)

    if bg_texture
      bg_texture.not_nil!.bind(Texture::Target::Texture2D) do
        bg_shader.use do |shader|
          shader.set_uniform("texture1", 0)

          vertex_array.bind do
            LibGL.draw_elements(LibGL::TRIANGLES, 6, DataType::UnsignedInt, Pointer(Void).new(0))
          end
        end
      end
    end

    frame[:tex].bind(Texture::Target::Texture2D) do
      buddy_shader.use do |shader|
        shader.set_uniform("texture1", 0)
        shader.set_uniform("funfriendSize", funfriend_size[:width].to_f32, funfriend_size[:height].to_f32)
        shader.set_uniform("resolution", window_width.to_f32, window_height.to_f32)
        shader.set_uniform("time", CrystGLFW.time.to_f32)

        vertex_array.bind do
          LibGL.draw_elements(LibGL::TRIANGLES, 6, DataType::UnsignedInt, Pointer(Void).new(0))
        end
      end
    end
  end

  def clean_up
    {vertex_array, vertex_buffer}.each { |v| v.delete }
  end
end