Simulation of live plotting from received packets using GR.jl in Julia

gr_live_window.jl

# gr_live_window.jl
using GR

function keyboard_channel()
    # allow 'q' and <ENTER> sequentially pressed on the keyboard to break the loop
    count = 0
    kb2loop = Channel(10)
    @async while true
        kb_input = readline(STDIN)
        # maybe we hit an error or something got messed up... 
        # just break and relinquish STDIN
        if (count+=1) >= 5
            break
        end

        if contains(lowercase(kb_input), "q")
            put!(kb2loop, "quit")
            break
        end
    end
    return kb2loop
end

function gr_custom_plot(x, y; xylims=nothing)
    GR.setviewport(0.03, 0.97, 0.05, 0.95)
    # GR.setlinecolorind(218)
    # GR.setfillintstyle(1)
    # GR.setfillcolorind(208)
    # GR.updatews()

    if xylims==nothing
        xylims = (minimum(x), maximum(x), minimum(y), maximum(y))
    end

    GR.clearws()
    GR.setwindow(xylims...)
    GR.fillrect(xylims...)
    GR.grid(
        (xylims[2]-xylims[1])/10, 
        (xylims[4]-xylims[3])/10,
        xylims[1], 0, 5, 5
    )
    GR.axes( 
        1, #(xylims[2]-xylims[1])/30, 
        (xylims[4]-xylims[3])/30,
        xylims[1], xylims[3], 
        5, 5, 0.01
    )
    GR.polyline(x, y)
    # GR.polymarker(x, y)
    GR.updatews()
end

 

function gr_live_window(; timeout=3600, fps_update=false)
    # convenient constants
    fs = 10
    winsec = 30
    hopsec = 1
    nwin = round(Integer, winsec*fs)
    nhop = round(Integer, hopsec*fs)

    # let user interrupt the live plot
    kb2loop = keyboard_channel()

    # do the loop
    frame_start = -winsec
    frame_time = collect( (0:(nwin-1)) * (1/fs) )

    print("I: Warming up the plotting engine... "); t1=time()
    gr_custom_plot(frame_start + frame_time, zeros(Float32, nwin))
    println("FINISHED [$(round(time()-t1,3)) s]")

    fix = 0 # frame index
    # f0 = 0.5 # Hz
    fps_slide = 30
    tslide = 1/fps_slide
    start_time = time()
    aframe = zeros(Float32, nwin)
    while time() - start_time < timeout
        if isready(kb2loop) && "quit"==take!(kb2loop)
            break
        end

        # aframe = sin.(2*pi*f0.*(frame_start + frame_time))
        append!(aframe, randn(nhop)); deleteat!(aframe, 1:nhop)
        println("fix = $(fix+=1) @ $(time() - start_time)")
        gr_custom_plot(frame_start + frame_time, aframe)
        
        # this attempts to smoothly update at some fps or frames-per-second
        if fps_update
            xylims = [frame_start, frame_start+frame_time[end], minimum(aframe), maximum(aframe)]
            for ix=1:fps_slide
                # 0.9 is just a guess of (1-x) where x is the ratio
                #     (time of gr_custom_plot())  / (1/fps)
                sleep(tslide)
                xylims[1:2] += (tslide)
                gr_custom_plot(frame_start + frame_time, aframe; xylims=xylims)
            end
        else
            sleep(hopsec)
        end
        frame_start += hopsec
    end # while loop
    println("Finished in $(time() - start_time) seconds.")
end