[README,camera] Add camera management module.

README.ACKNOWLEDGEMENT

@@ -1,5 +1,6 @@
 The following files:
 
+* camera.lua
 * signal.lua
 * timer.lua
 

camera.lua

@@ -0,0 +1,175 @@
+--- Camera management class.
+--
+-- This is a reworked implementation of the original camera module
+-- from the hump library (https://github.com/vrld/hump).
+-- See README.ACKNOWLEDGEMENT for detailed information.
+--
+-- @module gear.camera
+-- @copyright 2010-2013 Matthias Richter
+-- @copyright 2022 The DoubleFourteen Code Forge
+-- @author Matthias Richter, Lorenzo Cogotti
+
+local Camera = { smooth = {} }
+Camera.__index = Camera
+
+
+function Camera.smooth.none()
+    return function (dx, dy) return dx, dy end
+end
+
+function Camera.smooth.linear(speed)
+    if type(speed) ~= 'number' then
+        error("Invalid parameter: speed = "..tostring(speed))
+    end
+
+    local getDelta = love.timer.getDelta
+    local min = math.min
+    local sqrt = math.sqrt
+
+    return function (dx,dy, s)
+        -- normalize direction
+        local d = sqrt(dx*dx + dy*dy)
+        local dts = min((s or speed) * getDelta(), d)  -- prevent overshooting the goal
+
+        if d > 0 then
+            dx,dy = dx/d, dy/d
+        end
+
+        return dx*dts, dy*dts
+    end
+end
+
+function Camera.smooth.damped(stiffness)
+    if type(stiffness) ~= 'number' then
+        error("Invalid parameter: stiffness = "..tostring(stiffness))
+    end
+
+    local getDelta = love.timer.getDelta
+
+    return function (dx,dy, s)
+        local dts = (s or stiffness) * getDelta()
+
+        return dx*dts, dy*dts
+    end
+end
+
+function Camera:new(args)
+    self = setmetatable(args or {}, self)
+    self.x = self.x or love.graphics.getWidth()/2
+    self.y = self.y or love.graphics.getHeight()/2
+    self.rot = self.rot or 0
+    self.scale = self.scale or 1
+    self.smoother = self.smoother or self.smooth.none() -- for locking, see below
+
+    return self
+end
+
+function Camera:move(dx, dy)
+    self.x, self.y = self.x + dx, self.y + dy
+end
+
+function Camera:zoom(mul)
+    self.scale = self.scale * mul
+end
+
+function Camera:attach(x,y,w,h, noclip)
+    x, y = x or 0, y or 0
+    w, h = w or love.graphics.getWidth(), h or love.graphics.getHeight()
+
+    self._sx,self._sy,self._sw,self._sh = love.graphics.getScissor()
+    if not noclip then
+        love.graphics.setScissor(x, y, w, h)
+    end
+
+    local cx, cy = x + w/2, y + h/2
+
+    love.graphics.push()
+    love.graphics.translate(cx, cy)
+    love.graphics.scale(self.scale)
+    love.graphics.rotate(self.rot)
+    love.graphics.translate(-self.x, -self.y)
+end
+
+function Camera:detach()
+    love.graphics.pop()
+    love.graphics.setScissor(self._sx,self._sy,self._sw,self._sh)
+end
+
+local cos, sin = math.cos, math.sin
+
+-- world coordinates to Camera coordinates
+function Camera:tocamera(x,y, ox,oy,w,h)
+    ox, oy = ox or 0, oy or 0
+    w, h = w or love.graphics.getWidth(), h or love.graphics.getHeight()
+
+    -- x,y = ((x,y) - (self.x, self.y)):rotated(self.rot) * self.scale + center
+    local c, s = cos(self.rot), sin(self.rot)
+
+    x, y = x - self.x, y - self.y
+    x, y = c*x - s*y, s*x + c*y
+    return x*self.scale + w/2 + ox, y*self.scale + h/2 + oy
+end
+
+-- Camera coordinates to world coordinates
+function Camera:toworld(x,y, ox,oy,w,h)
+    ox, oy = ox or 0, oy or 0
+    w, h = w or love.graphics.getWidth(), h or love.graphics.getHeight()
+
+    -- x,y = (((x,y) - center) / self.scale):rotated(-self.rot) + (self.x,self.y)
+    local c,s = cos(-self.rot), sin(-self.rot)
+
+    x,y = (x - w/2 - ox) / self.scale, (y - h/2 - oy) / self.scale
+    x,y = c*x - s*y, s*x + c*y
+    return x+self.x, y+self.y
+end
+
+function Camera:mousepos(ox,oy,w,h)
+    local mx, my = love.mouse.getPosition()
+
+    return self:toworld(mx,my, ox,oy,w,h)
+end
+
+-- Camera scrolling utilities
+function Camera:lockx(x, smoother, ...)
+    local dx, dy = (smoother or self.smoother)(x - self.x, self.y, ...)
+
+    self.x = self.x + dx
+end
+
+function Camera:locky(y, smoother, ...)
+    local dx, dy = (smoother or self.smoother)(self.x, y - self.y, ...)
+
+    self.y = self.y + dy
+end
+
+function Camera:lockpos(x,y, smoother, ...)
+    return self:move((smoother or self.smoother)(x - self.x, y - self.y, ...))
+end
+
+function Camera:lockwindow(x, y, xmin, xmax, ymin, ymax, smoother, ...)
+    -- Figure out displacement in Camera coordinates
+    x, y = self:tocamera(x,y)
+
+    local dx, dy = 0,0
+
+    if x < xmin then
+        dx = x - xmin
+    elseif x > xmax then
+        dx = x - xmax
+    end
+    if y < ymin then
+        dy = y - ymin
+    elseif y > ymax then
+        dy = y - ymax
+    end
+
+    -- Transform displacement to movement in world coordinates
+    local c, s = cos(-self.rot), sin(-self.rot)
+
+    dx, dy = (c*dx - s*dy) / self.scale, (s*dx + c*dy) / self.scale
+
+    -- Move
+    self:move((smoother or self.smoother)(dx,dy,...))
+end
+
+return Camera