low_resolution_canvas.rb

# Copyright (c) 2020 Kevin Fischer
# https://github.com/kfischer-okarin/dragonruby-toolbox
# Released under the MIT License (see repository)

module DRT
  # Add your primitives to the {#labels}, {#lines}, {#solids}, {#borders}, {#sprites} and {#primitives} properties of
  # this object and then add this object to `args.outputs.sprites` or `args.outputs.primitives` to create a pixel
  # perfect canvas with a resolution lower than 1280x720.
  #
  # @example Render a label to a 64x64 canvas
  #   def tick(args)
  #     args.state.canvas ||= DRT::LowResolutionCanvas.new([64, 64])
  #
  #     args.state.canvas.background_color = [255, 255, 255]
  #     args.state.canvas.labels << [20, 60, 'test']
  #
  #     args.outputs.primitives << args.state.canvas
  #   end
  class LowResolutionCanvas
    attr_sprite

    def initialize(resolution, render_target_name = :screen)
      @path = render_target_name
      @source_x = @source_y = 0
      @source_w, @source_h = resolution

      # Scale and center renter target to real screen size
      @w = @source_w * scale
      @h = @source_h * scale
      @x = ($args.grid.w - @w).idiv 2
      @y = ($args.grid.h - @h).idiv 2
    end

    def labels
      render_target.labels
    end

    def lines
      render_target.lines
    end

    def solids
      render_target.solids
    end

    def borders
      render_target.borders
    end

    def sprites
      render_target.sprites
    end

    def primitives
      render_target.primitives
    end

    def background_color=(color)
      render_target.background_color = color
    end

    def to_screen_point(point)
      [@x + point.x * scale, @y + point.y * scale]
    end

    def to_screen_rect(rect)
      [*to_screen_point(rect), rect.w * scale, rect.h * scale]
    end

    private

    def scale
      @scale ||= [$args.grid.w.idiv(@source_w), $args.grid.h.idiv(@source_h)].min
    end

    def render_target
      $args.render_target(@path)
    end
  end
end