perf.lua

local histograms = {}

local function make_debug_histogram(name, length, pattern)
    return {
        name = name,
        times = {},
        writes = 0,
        length = length,
        pattern = pattern
    }
end

local function histogram_insert_value(histogram, value)
    histogram.times[(histogram.writes % histogram.length) + 1] = value
    histogram.writes = histogram.writes + 1
end

local function histogram_values(histogram)
    local lower_bound = histogram.writes % histogram.length
    local upper_bound = lower_bound + histogram.length
    local index = lower_bound

    return function()
        if (index == upper_bound) then
            return nil
        end

        local value = histogram.times[(index % histogram.length) + 1] or 0

        index = index + 1

        return (index - lower_bound), value
    end
end

function debug_plot_over_time(name, value, pattern)
    local histogram = histograms[name]

    if not histogram then
        histogram = make_debug_histogram(name, 300, pattern)
        histograms[name] = histogram
    end

    histogram_insert_value(histogram, value)
end

local function draw_histogram(histogram, x, y, height)
    local max_value = -0xffffff
    local min_value = 0xffffff
    local sum = 0

    for _, value in ipairs(histogram.times) do
        max_value = math.max(value, max_value)
        min_value = math.min(value, min_value)

        sum = sum + value
    end

    local avg = sum / histogram.length

    love.graphics.setColor(1, 0, 0)

    for index, value in histogram_values(histogram) do
        local line_height = (value / max_value) * height
        love.graphics.line(x + index, y, x + index, y - line_height)
    end

    local text = string.format("%s, avg: " .. histogram.pattern, histogram.name, avg)
    love.graphics.print(text, x, y + 6)
    love.graphics.print(string.format(histogram.pattern, max_value), x - 60, y - height)
    love.graphics.print(string.format(histogram.pattern, min_value), x - 60, y - (min_value / max_value) * height)
end

function draw_histograms()
    local screen_width = love.graphics.getWidth()
    local y = 140

    for _, histogram in pairs(histograms) do
        draw_histogram(histogram, screen_width - histogram.length - 10, y, 100)
        y = y + 140
    end
end

function do_and_measure_ms(func, ...)
    local t = love.timer.getTime()

    func(...)

    return (love.timer.getTime() - t) * 1000
end