center.lua

local center = {}

function center:setupScreen(width, height)
    self._WIDTH = width
    self._HEIGHT = height
    self._MAX_WIDTH = 0
    self._MAX_HEIGHT = 0
    self._MAX_RELATIVE_WIDTH = 0
    self._MAX_RELATIVE_HEIGHT = 0
    self._SCREEN_WIDTH = love.graphics.getWidth()
    self._SCREEN_HEIGHT = love.graphics.getHeight()
    self._BORDERS = {
        ['t'] = 0,
        ['r'] = 0,
        ['b'] = 0,
        ['l'] = 0
    }
    self:apply()
    return self
end

function center:setBorders(top, right, bottom, left)
    self._BORDERS.t = top
    self._BORDERS.r = right
    self._BORDERS.b = bottom
    self._BORDERS.l = left
end

function center:setMaxWidth(width)
    self._MAX_WIDTH = width
end

function center:setMaxHeight(height)
    self._MAX_HEIGHT = height
end

function center:setMaxRelativeWidth(width)
    self._MAX_RELATIVE_WIDTH = width
end

function center:setMaxRelativeHeight(height)
    self._MAX_RELATIVE_HEIGHT = height
end

function center:resize(width, height)
    self._SCREEN_WIDTH = width
    self._SCREEN_HEIGHT = height
    self:apply()
end

function center:apply()
    local available_width = self._SCREEN_WIDTH - self._BORDERS.l - self._BORDERS.r
    local available_height = self._SCREEN_HEIGHT - self._BORDERS.t - self._BORDERS.b
    local max_width = available_width
    local max_height = available_height
    if self._MAX_RELATIVE_WIDTH > 0 and available_width * self._MAX_RELATIVE_WIDTH < max_width then
        max_width = available_width * self._MAX_RELATIVE_WIDTH
    end
    if self._MAX_RELATIVE_HEIGHT > 0 and available_height * self._MAX_RELATIVE_HEIGHT < max_height then
        max_height = available_height * self._MAX_RELATIVE_HEIGHT
    end
    if self._MAX_WIDTH > 0 and self._MAX_WIDTH < max_width then
        max_width = self._MAX_WIDTH
    end
    if self._MAX_HEIGHT > 0 and self._MAX_HEIGHT < max_height then
        max_height = self._MAX_HEIGHT
    end
    if max_height / max_width > self._HEIGHT / self._WIDTH then
        self._CANVAS_WIDTH = max_width
        self._CANVAS_HEIGHT = self._CANVAS_WIDTH * (self._HEIGHT / self._WIDTH)
    else
        self._CANVAS_HEIGHT = max_height
        self._CANVAS_WIDTH = self._CANVAS_HEIGHT * (self._WIDTH / self._HEIGHT)
    end
    self._SCALE = self._CANVAS_HEIGHT / self._HEIGHT
    self._OFFSET_X = self._BORDERS.l + (available_width - self._CANVAS_WIDTH) / 2
    self._OFFSET_Y = self._BORDERS.t + (available_height - self._CANVAS_HEIGHT) / 2
end

function center:start()
    love.graphics.push()
    love.graphics.translate(self._OFFSET_X, self._OFFSET_Y)
    love.graphics.scale(self._SCALE, self._SCALE)
end

function center:finish()
    love.graphics.pop()
end

function center:toGame(x, y)
    return (x - self._OFFSET_X) / self._SCALE,
           (y - self._OFFSET_Y) / self._SCALE
end

return center