Use time.sleep() to draw and remove objects delayed

[Rene36]

Hi everyone,

I enjoy using SimpInkScr a lot and lately I was trying the following, which unfortunately did not work as expected:
I draw two rectangles, wait for 5 seconds and then remove all objects. I would like to make small animations. However, time.sleep() somehow executes not in the correct order:

import time

rect((0, 0), (200, 100), fill='#FF7F2A')
rect((18, 33), (18+30, 33+30), fill='#C8B7B7')
time.sleep(5)
for s in all_shapes():
    s.remove()

I do not see anything on the canvas, when running the above code. Probably, because the two rectangles are drawn, removed and then the script is sleeping for 5 seconds. However, I would like to actually see the two rectangles for 5 seconds and then remove them.

Everything works as expected though, when starting with the sleep call:

import time

time.sleep(5)
rect((0, 0), (200, 100), fill='#FF7F2A')
rect((18, 33), (18+30, 33+30), fill='#C8B7B7')

Does anybody have an idea why time.sleep() seems to be executed in an arbitrary order and is there another way to pause / stop the script for a given period of time?

Any help or ideas are highly appreciated :).

[spakin]

Unfortunately, Inkscape extensions can't render animations like you'd hope. Modifications to the image are applied all at once and only if the extension returns a success code. That's why in your first script, you see nothing on the canvas: the final canvas state at the end of the script, which happened to take 5s to run, has no new rectangles on it. By the same logic, the final canvas state at the end of your second script, which also takes 5s to run, has two new rectangles on it. In other words, no reordering is occurring; the canvas simply is not updating in real time.

Let me instead recommend using Simple Inkscape Scripting's animate method to produce an animated SVG file. The result will not appear animated in Inkscape itself, but if you save the canvas to an SVG file and open it in a web browser, it should do what you want.

Here's how I'd make the rectangles disappear after five seconds:

r1 = rect((0, 0), (200, 100), fill='#FF7F2A', opacity=1)
r2 = rect((18, 33), (18+30, 33+30), fill='#C8B7B7', opacity=1)
invisible = rect((0, 0), (1, 1), opacity=0)
anim_params = {
    'duration': '5s',
    'key_times': [0.0, 1.0],
    'attr_filter': lambda a: a == 'opacity',
    'interpolation': 'discrete',
}
r1.animate(invisible, **anim_params)
r2.animate(invisible, **anim_params)

By way of explanation,

1. The first two lines create the two rectangles, naming them r1 and r2. The call to rect explicitly specifies 100% opacity to make this attribute eligible for animation.
2. The next line creates a dummy rectangle, invisible, with 0% opacity.
3. To reduce repetition, animation parameters are stored in a dictionary, anim_params, so they can be reused by each of the two colored rectangles.
   • The duration is set to five seconds.
   • Visual changes happen at the 0% (0s) and 100% (5s) offsets.
   • Only opacity should be animated, not, e.g., the rectangles' size or position.
   • The opacity should change abruptly, not smoothly. (Remove the interpolation setting to see what a smooth transition looks like.)
4. The final two lines animate each of r1 and r2, specifying that they should adopt invisible's attributes according to the animation parameters. If you really want to delete all shapes, not just the two rectangles, you can invoke animate on each shape found in all_shapes().

I hope that helps.

[Rene36]

Thanks a lot for the quick and helpful reply.