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- Committer: Josh C
- Date: 2013-08-24 03:11:38 UTC
- Revision ID: josh@9ix.org-20130824031138-j4ta4ome0upsxcv5
zoetrope 1.4
- files added:
- zoetrope
- zoetrope/core
- zoetrope/input
- zoetrope/sprites
- zoetrope/ui
- zoetrope/utils
added
removed
zoetrope/core/sprite.lua
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-- Class: Sprite
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-- A sprite receives all update-related events and draws
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-- itself onscreen with its draw() method. It is defined
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-- by a rectangle; nothing it draws should be outside that
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-- rectangle.
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--
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-- In most cases, you don't want to create a sprite directly.
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-- Instead, you'd want to use a subclass tailored to your needs.
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-- Create a new subclass if you need to heavily customize how a
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-- sprite is drawn onscreen.
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--
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-- If you don't need something to display onscreen, just
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-- to listen to updates, set the sprite's visible property to false.
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--
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-- Extends:
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-- <Class>
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--
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-- Event: onUpdate
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-- Called once each frame, with the elapsed time since the last frame in seconds.
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--
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-- Event: onBeginFrame
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-- Called once each frame like onUpdate, but guaranteed to fire before any others' onUpdate handlers.
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--
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-- Event: onEndFrame
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-- Called once each frame like onUpdate, but guaranteed to fire after all others' onUpdate handlers.
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--
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-- Event: onCollide
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-- Called when the sprite intersects another during a collide() call. When a collision is detected,
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-- this event occurs for both sprites. The sprite is passed three arguments: the other sprite, the
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-- horizontal overlap, and the vertical overlap between the other sprite, in pixels.
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Sprite = Class:extend
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{
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-- Property: active
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-- If false, the sprite will not receive an update-related events.
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active = true,
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-- Property: visible
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-- If false, the sprite will not draw itself onscreen.
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visible = true,
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-- Property: solid
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-- If false, the sprite will never be eligible to collide with another one.
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-- It will also never displace another one.
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solid = true,
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-- Property: x
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-- Horizontal position in pixels. 0 is the left edge of the window.
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x = 0,
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-- Property: y
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-- Vertical position in pixels. 0 is the top edge of the window.
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y = 0,
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-- Property: width
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-- Width in pixels.
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-- Property: height
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-- Height in pixels.
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-- Property: rotation
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-- Rotation of drawn sprite in radians. This does not affect the bounds
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-- used during collision checking.
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rotation = 0,
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-- Property: velocity
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-- Motion either along the x or y axes, or rotation about its center, in
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-- pixels per second.
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velocity = { x = 0, y = 0, rotation = 0 },
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-- Property: minVelocity
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-- No matter what else may affect this sprite's velocity, it
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-- will never go below these numbers.
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minVelocity = { x = - math.huge, y = - math.huge, rotation = - math.huge },
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-- Property: maxVelocity
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-- No matter what else may affect this sprite's velocity, it will
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-- never go above these numbers.
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maxVelocity = { x = math.huge, y = math.huge, rotation = math.huge },
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-- Property: acceleration
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-- Acceleration along the x or y axes, or rotation about its center, in
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-- pixels per second squared.
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acceleration = { x = 0, y = 0, rotation = 0 },
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-- Property: drag
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-- This property is only active when the related acceleration is 0. In those
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-- instances, it applies acceleration towards 0 for the given property. i.e.
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-- when the velocity is positive, it applies a negative acceleration.
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drag = { x = 0, y = 0, rotation = 0 },
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-- Property: scale
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-- This affects how the sprite is drawn onscreen. e.g. a sprite with scale 2 will
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-- display twice as big. Scaling is centered around the sprite's center. This has
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-- no effect on collision detection.
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scale = 1,
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-- Property: distort
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-- This allows you to scale a sprite in a distorted fashion by defining ratios
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-- between x and y scales.
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distort = { x = 1, y = 1 },
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-- Property: flipX
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-- If set to true, then the sprite will draw flipped horizontally.
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flipX = false,
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-- Property: flipY
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-- If set to true, then the sprite will draw flipped vertically.
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flipY = false,
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-- Property: alpha
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-- This affects the transparency at which the sprite is drawn onscreen. 1 is fully
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-- opaque; 0 is completely transparent.
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alpha = 1,
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-- Property: tint
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-- This tints the sprite a color onscreen. This goes in RGB order; each number affects
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-- how that particular channel is drawn. e.g. to draw the sprite in red only, set tint to
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-- { 1, 0, 0 }.
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tint = { 1, 1, 1 },
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-- Method: die
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-- Makes the sprite totally inert. It will not receive
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-- update events, draw anything, or be collided.
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--
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-- Arguments:
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-- none
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--
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-- Returns:
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-- nothing
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die = function (self)
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self.active = false
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self.visible = false
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self.solid = false
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end,
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-- Method: revive
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-- Makes this sprite completely active. It will receive
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-- update events, draw itself, and be collided.
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--
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-- Arguments:
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-- none
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--
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-- Returns:
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-- nothing
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revive = function (self)
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self.active = true
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self.visible = true
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self.solid = true
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end,
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-- Method: intersects
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-- Returns whether a point or rectangle intersects this sprite.
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--
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-- Arguments:
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-- x - top left horizontal coordinate
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-- y - top left vertical coordinate
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-- width - width of the rectangle, omit for points
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-- height - height of the rectangle, omit for points
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--
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-- Returns:
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-- boolean
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intersects = function (self, x, y, width, height)
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return self.x < x + (width or 0) and self.x + self.width > x and
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self.y < y + (height or 0) and self.y + self.height > y
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end,
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-- Method: overlap
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-- Returns the horizontal and vertical overlap of this sprite
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-- and a rectangle. This ignores the sprite's <solid> property
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-- and does not trigger any <onCollide> events.
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--
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-- Arguments:
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-- x - top left horizontal coordinate
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-- y - top left vertical coordinate
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-- width - width of the rectangle
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-- height - height of the rectangles
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--
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-- Returns:
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-- Two numbers: horizontal overlap in pixels, and vertical overlap in pixels.
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overlap = function (self, x, y, width, height)
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local selfRight = self.x + self.width
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local selfBottom = self.y + self.height
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local right = x + width
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local bottom = y + height
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-- this is cribbed from
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-- http://frey.co.nz/old/2007/11/area-of-two-rectangles-algorithm/
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if self.x < right and selfRight > x and
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self.y < bottom and selfBottom > y then
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return math.min(selfRight, right) - math.max(self.x, x),
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math.min(selfBottom, bottom) - math.max(self.y, y)
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else
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return 0, 0
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end
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end,
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-- Method: collide
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-- Checks whether this sprite collides with other <Sprite>s ad <Group>s. If a collision is detected,
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-- onCollide() is called on both this sprite and the one it collides with, passing
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-- the amount of horizontal and vertical overlap between the sprites in pixels.
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--
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-- Arguments:
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-- ... - any number of <Sprite>s or <Group>s to collide with.
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--
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-- Returns:
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-- nothing
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collide = function (self, ...)
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Collision:check(self, ...)
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end,
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-- Method: displace
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-- Displaces another sprite or group so that it no longer overlaps this one.
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-- This by default seeks to move the other sprite the least amount possible.
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-- You can give this function a hint about which way it ought to move the other
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-- sprite (e.g. by consulting its current motion) through the two optional
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-- arguments. A single displace() call will *either* move the other sprite
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-- horizontally or vertically, not along both axes.
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--
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-- This does *not* cause onCollide events to occur on the sprites.
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--
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-- Arguments:
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-- other - sprite or group to displace
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-- xHint - force horizontal displacement in one direction, uses direction constants, optional
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-- yHint - force vertical displacement in one direction, uses direction constants, optional
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--
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-- Returns:
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-- nothing
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displace = function (self, other, xHint, yHint)
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if not self.solid or self == other or not other.solid then return end
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if STRICT then assert(other:instanceOf(Sprite), 'asked to displace a non-sprite') end
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local xChange = 0
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local yChange = 0
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if other.sprites then
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-- handle groups
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for _, spr in pairs(other.sprites) do
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self:displace(spr, xHint, yHint)
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end
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else
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-- handle sprites
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local xOverlap, yOverlap = self:overlap(other.x, other.y, other.width, other.height)
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-- resolve horizontal overlap
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if xOverlap ~= 0 then
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local leftMove = (other.x - self.x) + other.width
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local rightMove = (self.x + self.width) - other.x
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if xHint == LEFT then
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xChange = - leftMove
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elseif xHint == RIGHT then
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xChange = rightMove
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else
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if leftMove < rightMove then
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xChange = - leftMove
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else
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xChange = rightMove
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end
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end
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end
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-- resolve vertical overlap
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if yOverlap ~= 0 then
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local upMove = (other.y - self.y) + other.height
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local downMove = (self.y + self.height) - other.y
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if yHint == UP then
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yChange = - upMove
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elseif yHint == DOWN then
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yChange = downMove
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else
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if upMove < downMove then
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yChange = - upMove
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else
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yChange = downMove
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end
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end
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end
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-- choose the option that moves the other sprite the least
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if math.abs(xChange) > math.abs(yChange) then
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other.y = other.y + yChange
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else
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other.x = other.x + xChange
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end
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end
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end,
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-- Method: push
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-- Moves another sprite as if it had the same motion properties as this one.
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--
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-- Arguments:
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-- other - other sprite to push
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-- elapsed - elapsed time to simulate, in seconds
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--
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-- Returns:
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-- nothing
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push = function (self, other, elapsed)
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other.x = other.x + self.velocity.x * elapsed
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other.y = other.y + self.velocity.y * elapsed
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end,
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-- Method: distanceTo
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-- Returns the distance from this sprite to either another sprite or
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-- an arbitrary point. This uses the center of sprites to calculate the distance.
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--
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-- Arguments:
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-- Can be either one argument, a sprite (or any other table with x
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-- and y properties), or two arguments, which correspond to a point.
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--
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-- Returns:
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-- distance in pixels
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distanceTo = function (self, ...)
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local arg = {...}
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local midX = self.x + self.width / 2
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local midY = self.y + self.width / 2
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if #arg == 1 then
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local spr = arg[1]
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if STRICT then
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assert(type(spr.x) == 'number' and type(spr.y) == 'number', 'asked to calculate distance to an object without numeric x and y properties')
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end
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local sprX = spr.x + spr.width / 2
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local sprY = spr.y + spr.height / 2
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return math.sqrt((midX - sprX)^2 + (midY - sprY)^2)
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else
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return math.sqrt((midX - arg[1])^2 + (midY - arg[2])^2)
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end
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end,
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startFrame = function (self, elapsed)
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if self.onStartFrame then self:onStartFrame(elapsed) end
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end,
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update = function (self, elapsed)
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local vel = self.velocity
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local acc = self.acceleration
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local drag = self.drag
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local minVel = self.minVelocity
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local maxVel = self.maxVelocity
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-- check existence of properties
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if STRICT then
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assert(vel, 'active sprite has no velocity property')
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assert(acc, 'active sprite has no acceleration property')
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assert(drag, 'active sprite has no drag property')
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assert(minVel, 'active sprite has no minVelocity property')
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assert(maxVel, 'active sprite has no maxVelocity property')
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end
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vel.x = vel.x or 0
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vel.y = vel.y or 0
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vel.rotation = vel.rotation or 0
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-- physics
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if vel.x ~= 0 then self.x = self.x + vel.x * elapsed end
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if vel.y ~= 0 then self.y = self.y + vel.y * elapsed end
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if vel.rotation ~= 0 then self.rotation = self.rotation + vel.rotation * elapsed end
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if acc.x and acc.x ~= 0 then
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vel.x = vel.x + acc.x * elapsed
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else
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if drag.x then
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if vel.x > 0 then
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vel.x = vel.x - drag.x * elapsed
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if vel.x < 0 then vel.x = 0 end
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elseif vel.x < 0 then
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vel.x = vel.x + drag.x * elapsed
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if vel.x > 0 then vel.x = 0 end
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end
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end
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end
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if acc.y and acc.y ~= 0 then
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vel.y = vel.y + acc.y * elapsed
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else
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if drag.y then
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if vel.y > 0 then
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vel.y = vel.y - drag.y * elapsed
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if vel.y < 0 then vel.y = 0 end
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elseif vel.y < 0 then
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vel.y = vel.y + drag.y * elapsed
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if vel.y > 0 then vel.y = 0 end
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end
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end
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end
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if acc.rotation and acc.rotation ~= 0 then
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vel.rotation = vel.rotation + acc.rotation * elapsed
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else
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if drag.rotation then
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if vel.rotation > 0 then
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vel.rotation = vel.rotation - drag.rotation * elapsed
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if vel.rotation < 0 then vel.rotation = 0 end
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elseif vel.rotation < 0 then
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vel.rotation = vel.rotation + drag.rotation * elapsed
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if vel.rotation > 0 then vel.rotation = 0 end
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end
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end
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end
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if minVel.x and vel.x < minVel.x then vel.x = minVel.x end
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if maxVel.x and vel.x > maxVel.x then vel.x = maxVel.x end
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if minVel.y and vel.y < minVel.y then vel.y = minVel.y end
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if maxVel.y and vel.y > maxVel.y then vel.y = maxVel.y end
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if minVel.rotation and vel.rotation < minVel.rotation then vel.rotation = minVel.rotation end
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if maxVel.rotation and vel.rotation > maxVel.rotation then vel.rotation = maxVel.rotation end
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if self.onUpdate then self:onUpdate(elapsed) end
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end,
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endFrame = function (self, elapsed)
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if self.onEndFrame then self:onEndFrame(elapsed) end
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end,
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draw = function (self, x, y)
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-- subclasses do interesting things here
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end,
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collidedWith = function (self, other, xOverlap, yOverlap)
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if self.onCollide then self:onCollide(other, xOverlap, yOverlap) end
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end
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}
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