Problem with widgets in vpython 7

[Avedis Neehus]

Clicking on the button 'add E field' causes the programm to crash without giving an error. The relevant code can be found inside the gui class. https://github.com/Avedis-Neehus/3D-EM-Balls/blob/gui/3DEMtest.py

[Bruce Sherwood]

The problem is this:

from vpython import *

def make_text():

    print('make_text')

    T = text(text='abc')

    print(T.text)

#make_text() # this works

button(bind=make_text, text='Try') # text creation fails when clicked

I don't know what causes this, though it has to be related to the fact that creating a 3D text object requires a kind of wait state in Python to receive from the browser the final data on the text object (such as its length), before continuing to the next statement.

There is a very simple fix, which is to delete or comment out your large number of 3D text objects, none of which will be seen, because the default height is 1 but your scene is much larger than that.

Thanks for the report. It must be the case that no one up to now has tried to create a 3D text object inside a function that is bound to a mouse event.

Bruce

[Bruce Sherwood]

For completeness I should add that the bug is not present in GlowScript VPython, where there is no wait state when a 3D text object is created, because everything is in the browser.

Bruce

[Bruce Sherwood]

The VPython 7 bug is present not only for 3D text but also for compound and extrusion (all of these have to wait for information from the browser).

Bruce

[Avedis Neehus]

I just noticed that what I actually wanted to use is wtext() not text() so the bug doesn't affect my programm . By the way, is it possible to use the space to the right of the animation?

2017-10-26 3:28 GMT+02:00 Bruce Sherwood <bruce.s...@gmail.com>:

The VPython 7 bug is present not only for 3D text but also for compound and extrusion (all of these have to wait for information from the browser).

Bruce

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[Bruce Sherwood]

Yes, see the "align" attribute at

http://www.glowscript.org/docs/VPythonDocs/canvas.html

Bruce

[Russell Kramer]

Has this issue been fixed for compound or extrusion objects or is there a work around?

I have a program https://github.com/northcoastmountainrat/Sitchensis that plots complex 3d trees.

Documented Issue #14 therein is related to this problem... I think. 

I want to include all the code in the MainBodyScript.py file into a main() function so I can call it from the command line and pass some arguments that control its output. 

When I do this none of the widgets work any longer. They work fine if I leave the MainBodyScript as it is. 

Thank you, 

Russell Kramer

[Bruce Sherwood]

I tried the following in Spyder and it works correctly:

from vpython import *

box(pos=vec(-1,0,0))

def make_text():

    print('make_text')

    T = text(text='abc')

    s = sphere(pos=vec(1,-1,0), radius=0.2, color=color.red)

    c = cone(pos=vec(1,-1,0), radius=0.1, color=color.cyan)

    cmp = compound([s,c], pos=vec(-1,1,0))

    print(T.text)

button(bind=make_text, text='Try')

[Russell Kramer]

My structure is actually slightly different, all the code is in the function so it can be called from the command line. In your example it would look like this:

def main():

    def make_text():
        print('make_text')
        T = text(text='abc')
        s = sphere(pos=vec(1,-1,0), radius=0.2, color=color.red)
        c = cone(pos=vec(1,-1,0), radius=0.1, color=color.cyan)
        cmp = compound([s,c], pos=vec(-1,1,0))
        print(T.text)
    button(bind=make_text, text='Try')

if __name__ == "__main__":
    main()

Then in the setup.py file there is an entry point that calls main.

setup( ... entry_points = { 'console_scripts': ['run_tree=folder.script:main'], } ... )

then from the command line:

python main

This outputs the figure but no working widgets. 

[Bruce Sherwood]

I don't understand your setup stuff, but the following program behaves as expected when running from Spyder:

from vpython import *