Script to handle display resizing in Löve2D

display.lua

local lg = love.graphics

local Display = {

    size  = {
        w = 0,
        h = 0,
        ox = 0,
        oy = 0
    };

    scale = {
        x = 1, y = 1,
        rx = 1, ry = 1
    };

    ratio = {

        value = 0,              -- Ratio value: GW/GH
        w = 0, h = 0,           -- Size of the display in the window
        offset_x = 0,           -- Display offset (to center the display in the window)
        offset_y = 0,

        bar_w = 0,              -- Bar size
        bar_h = 0,
        bar_offset_x = 0,       -- Bar offset
        bar_offset_y = 0,

    };

}

function Display:init(keep_ratio)
    self.base_width, self.base_height = lg.getDimensions()
    self.keep_ratio = keep_ratio
    self:resize()
end

-- Render scaled and translate --

function Display:push()

    local scale = self.scale
    local ratio = self.ratio

    lg.push()
    lg.translate(ratio.offset_x, ratio.offset_y)
    lg.scale(scale.x, scale.y)

end

function Display:pop()

    local ratio = self.ratio

    if self.keep_ratio then
        lg.setColor(0,0,0)
        lg.rectangle("fill", -ratio.bar_offset_x, -ratio.bar_offset_y, ratio.bar_offset_x, ratio.bar_h)
        lg.rectangle("fill", self.base_width, -ratio.bar_offset_y, ratio.bar_offset_x, ratio.bar_h)
        lg.rectangle("fill", 0, -ratio.bar_offset_y, ratio.bar_w, ratio.bar_offset_y)
        lg.rectangle("fill", 0, self.base_height, ratio.bar_w, ratio.bar_offset_y)
        lg.setColor(1,1,1)
    end

    lg.pop()

end

function Display:render(drawable, ...)
    self:push(); drawable(...); self:pop()
end


-- Render unscaled and "untranslated" --

function Display:unScaledPush()

    local scale = self.scale
    local ratio = self.ratio

    lg.push()
    lg.translate(-ratio.offset_x*scale.rx, -ratio.offset_y*scale.rx)
    lg.scale(scale.rx, scale.ry)

end

function Display:unScaledPop()
    lg.pop()
end

function Display:renderUnScaled(drawable, ...)
    self:unScaledPush(); drawable(...); self:unScaledPop()
end

-- Resize function --

function Display:resize()

    local size = self.size
    local scale = self.scale
    local ratio = self.ratio

    local GW = self.base_width
    local GH = self.base_height

    size.w, size.h = lg.getDimensions()

    if self.keep_ratio then

        -- Calculation related to game display --

        local ratio_value = GH/GW
        local new_width, new_height = size.w, size.h

        if new_width * ratio_value > new_height then
            new_width = new_height / ratio_value
        else
            new_height = new_width * ratio_value
        end

        scale.x = new_width / GW
        scale.y = new_height / GH

        -- Calculation related to ratio and bars --

        ratio.value = ratio_value
        ratio.w, ratio.h = new_width, new_height
        ratio.offset_x = (size.w - new_width) / 2
        ratio.offset_y = (size.h - new_height) / 2

        ratio.bar_w = size.w / scale.x
        ratio.bar_h = size.h / scale.y
        ratio.bar_offset_x = (ratio.bar_w - GW) / 2
        ratio.bar_offset_y = (ratio.bar_h - GH) / 2

    else

        scale.x = size.w / GW
        scale.y = size.h / GH

        ratio.value = GW/GH
        ratio.w = size.w
        ratio.h = size.h

        ratio.offset_x = 0
        ratio.offset_y = 0
        ratio.bar_w = 0
        ratio.bar_h = 0
        ratio.bar_offset_x = 0
        ratio.bar_offset_y = 0

    end

    size.ox = size.w / 2
    size.oy = size.h / 2

    scale.rx = 1/scale.x
    scale.ry = 1/scale.y

end

function Display:toWorld(x,y)
    local s, r = self.scale, self.ratio
    return (x - r.offset_x) / s.x,
           (y - r.offset_y) / s.y
end

function Display:toScreen(x,y)
    local s, r = self.scale, self.ratio
    return (x * s.x) + r.offset_x,
           (y * s.y) + r.offset_y
end


return Display