AKnopf/edu_draw

module EduDraw
    # A Sheet is a 2D-Canvas that can be drawn on using {Pen}
    class Sheet < Gosu::Window

        # @private
        # All pens created by and for this sheet
        attr_reader :pens
        private :pens

        # Creates a new Sheet
        #
        # @param x [Fixnum] width in pixels
        # @param y [Fixnum] height in pixels
        # @param title [String] Caption of the window
        def initialize(x: 100, y: 100, title: "A blank sheet")
            super x, y, false
            self.caption = title
            @pens = []
        end


        # Creates a new {Pen} that draws on self
        #
        # @see Pen
        #
        # @param x [Fixnum] x-coordinate of starting position. Left is 0.
        # @param y [Fixnum] y-coordinate of starting position. Top is 0.
        # @param angle [Fixnum] Direction of pen in degree. 0 points to the right.
        # @param color [Gosu::Color] Color of the pen
        def new_pen(x: 0, y: 0, angle: 0, color: Pen::DEFAULT_COLOR)
            create_pen Pen, x, y, angle, color
        end

        # Create a new {AnimationPen} that draws something different each frame
        #
        # @see AnimationPen
        #
        # @param (see #new_pen)
        def new_animation_pen(x: 0, y: 0, angle: 0, color: Pen::DEFAULT_COLOR)
            create_pen AnimationPen, x, y, angle, color
        end

        private

            # Creates a pen of a certain kind
            #
            # @param kind [class] Class of the pen to create
            def create_pen(kind, x, y, angle, color)
                pen = kind.new x: x, y: y, angle: angle, color: color
                pens << pen
                pen
            end

            # Makes gosu display the system mouse cursor
            def needs_cursor?
                true
            end

            # Gosu hook method for drawing window content
            def draw
                pens.map(&:shapes).each do |shapes|
                    shapes.each do |shape|
                        method,*args = shape
                        send method, *args
                    end
                end
            end

            # Gosu hook method for updating game state before drawing
            # This is called once per frame
            def update
                pens.each &:update
                if button_down? Gosu::KbEscape
                    close
                end
            end
    end
end