drawsvg experiment, draw a fish timeline chart

mkchart.py

"""Draw a simple SVG timeline chart with Python."""
import sys

import drawsvg as draw

w = 1200
h = 800
ox = -100
oy = -400


def create_drawing() -> draw.Drawing:
    """Create a drawing with a timeline."""
    dw = draw.Drawing(w, h, origin=(ox, oy))
    # white background
    dw.append(draw.Rectangle(ox, oy, w, h, fill="#f0f0f0"))
    # |--+--+--+--| timeline
    #  Q1 Q2 Q3 Q4
    dw.append(draw.Lines(0, 0, 1000, 0, stroke="black", stroke_width=3))
    for line in range(0, 1001, 250):
        dw.append(draw.Lines(line, 10, line, -10, stroke="black", stroke_width=3))
    dw.append(draw.Text("Q1", 25, x=125, y=25, text_anchor="middle"))
    dw.append(draw.Text("Q2", 25, x=375, y=25, text_anchor="middle"))
    dw.append(draw.Text("Q3", 25, x=595, y=25, text_anchor="middle"))
    dw.append(draw.Text("Q4", 25, x=875, y=25, text_anchor="middle"))
    return dw


def draw_task(
    dw: draw.Drawing,  # drawing context
    text: str,  # text to lable task
    done: float,  # fraction done, 0-1
    pos: str,  # position in year, 0-1000
    dir: str = "up",  # up: below line sloping up, "down", above sloping down
) -> None:
    """Draw a task on the timeline."""
    slope = 0.5
    x0 = pos - 300 * slope
    y0 = 300
    x1 = pos
    y1 = 0
    off = -1
    if dir != "up":
        y0 *= -1
        off *= -1

    p = draw.Lines(  # done part of line, blue
        x0,
        y0,
        (x1 - x0) * done + x0,
        (y1 - y0) * done + y0,
        stroke="blue",
        stroke_width=3,
    )
    dw.append(p)
    p = draw.Lines(  # remaining part of line, red
        (x1 - x0) * done + x0,
        (y1 - y0) * done + y0,
        x1,
        y1,
        stroke="red",
        stroke_width=3,
    )
    dw.append(p)
    
    # Couldn't find a way to offset text from line, so draw a second, invisible
    # line to put the text on.
    offs = 33  # offset for two lines of text
    p = draw.Lines(x0 + offs * off, y0, x1 + offs * off, y1, stroke_width=0)
    dw.append(p)
    dw.append(draw.Text(text.split(r"\n"), 22, path=p))


def main() -> None:
    """Generate chart from inputs."""
    dw = create_drawing()
    with open(sys.argv[1]) as data:
        title = data.readline()
        tasks = list(i.split(None, 3) for i in data if i.strip())

    dw.append(draw.Text(title, 32, x=500, y=-360, text_anchor="middle"))

    for done_txt, pos_txt, dir, text in tasks:
        done = float(done_txt)
        pos = float(pos_txt)
        draw_task(dw, text, done, pos, dir)

    dw.save_svg(f"{sys.argv[2]}.svg")
    dw.save_png(f"{sys.argv[2]}.png")


main()