linear_animation.rb

# Copyright 2011, 2014 Exavideo LLC.
# 
# This file is part of Exaboard.
# 
# Exaboard is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
# 
# Exaboard is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
# 
# You should have received a copy of the GNU General Public License
# along with Exaboard.  If not, see <http://www.gnu.org/licenses/>.


##
# A simple linear animation - i.e. a value that goes from zero to one,
# or one to zero, in a uniform ramp over a certain number of frames.
class LinearAnimation
	IN = 0
	OUT = 1

	##
	# Initializes the animation.
	def initialize(direction=IN)
		@value = 0
		@total_frames = 0
		@frame = 0
		@direction = direction
		@transition_done_block = nil
	end

	##
	# Return true if the animation is fully in.
	def fully_in?
		@frame == @total_frames and @direction == IN
	end

	##
	# Return true if the animation is fully out.
	def fully_out?
		@frame == @total_frames and @direction == OUT
	end

	##
	# Return true if the animation is in or heading in.
	def in?
		@direction == IN
	end

	##
	# Return true if the animation is out or heading out.
	def out?
		@direction == OUT
	end

	##
	# Moves the animation to the next frame.
	def frame_advance
		if @total_frames > 0
			@frame += 1
			if @direction == IN
				@value = @frame.to_f / @total_frames.to_f
			else
				@value = 1.0 - (@frame.to_f / @total_frames.to_f)
			end

			if @frame == @total_frames
				@frame = 0
				@total_frames = 0

				if @transition_done_block
					# copy to temporary in case the block calls in or out
					the_block = @transition_done_block
					@transition_done_block = nil
					the_block.call
				end
			end
		end
	end

	##
	# Begin an animation from out (0) to in (1).
	def in(frames)
		if @total_frames == 0 and @value < 0.5
			@frame = 0
			@total_frames = frames
			@direction = IN

			if block_given?
				@transition_done_block = Proc.new { yield }
			end
		end
	end

	##
	# Begin an animation from in (1) to out (0)
	def out(frames)
		if @total_frames == 0 and @value > 0.5
			@frame = 0
			@total_frames = frames
			@direction = OUT

			if block_given?
				@transition_done_block = Proc.new { yield }
			end
		end
	end

	##
	# Immediately transition to the in (1) state.
	def cut_in
		@value = 1.0
	end

	##
	# Immediately transition to the out (0) state.
	def cut_out
		@value = 0.0
	end

	attr_reader :value
end