Thread: [Visualpython-users] Event-driven / callback programming of mouse or keyboard

Is there any way to do event-driven programming, with callbacks for mouse or keyboard events? I would rather not use the polling style shown in example on the web site.

e.g. 

onKey('a', processKeyA)

onMouseDown(processMouseDown)

onMouseDownOn(myCube, processMouseDownOnObject)

Thanks!

I can't think of a way to do that within the existing structure.

I'll mention that in the new GlowScript (glowscript.org:
JavaScript/CoffeeScript plus WebGl, based on the VPython design),
events are handled with callbacks.

Bruce Sherwood

On Mon, May 21, 2012 at 12:30 PM, Sophie <its...@ho...> wrote:
> Is there any way to do event-driven programming, with callbacks for mouse or keyboard events? I would rather not use the polling style shown in example on the web site.
>
> e.g.
>
> onKey('a', processKeyA)
>
> onMouseDown(processMouseDown)
>
> onMouseDownOn(myCube, processMouseDownOnObject)
>
> Thanks!

Bruce Sherwood answers :
> I can't think of a way to do that within the existing structure.
to:
> Sophie:
>> Is there any way to do event-driven programming, with callbacks for mouse or keyboard events? I would rather not use the polling style shown in example on the web site.
>>
Event-driven style is not magic, and if you will to pay the price of 
some indirections, YOU CAN implement it yourself. You may also introduce 
"user events" not related to any hardware action, but which implement 
asynchronous loops.

This small program is a very primitive "planetary system", with looping 
and mouse/keyboard control based on "events". Alt-click adds a random 
planet, just click stops the motion. There is nothing more.

http://users.info.unicaen.fr/~karczma/TEACH/Anima/Progs/psystem.py

Good luck.

Jerzy Karczmarczuk

I too thought of a way to introduce a callback, by using threads (this
is based on the scheme used in the graphing module, vis/graph.py, to
enable the feature that dragging the mouse shows crosshairs on a
graph).

from visual import *
import time
from threading import Thread, RLock

lock = RLock()

run = True

class timer(Thread): # This timer thread watches for mouse events.
    def run(self):
        global run
        while True:
            time.sleep(0.05)
            lock.acquire()
            if scene.mouse.clicked:
                scene.mouse.getclick()
                run = not run
            lock.release()

b = box()

thr = timer()
thr.start()

while True:
    rate(100)
    if run: b.rotate(angle=.01, axis=(0,1,0))

Bruce Sherwood :
> I too thought of a way to introduce a callback, by using threads (this
> is based on the scheme used in the graphing module, vis/graph.py, to
> enable the feature that dragging the mouse shows crosshairs on a
> graph).
>
> from visual import *
> ...
> while True:
>      rate(100)
>      if run: b.rotate(angle=.01, axis=(0,1,0))
This is nice and may be very useful; in general I think that VP is 
underused in the domain of simulation (+visu+measuring, for pedagogical 
purposes) despite quite a number of applications.

But you might remember our short discussion some months ago. I 
discovered that rate() doesn't work well with threads in general. This 
directive introduces a time-consumming loop. The event processing with 
timers should be low-level (in my understanding of this stuff).

The best.

Jerzy Karczmarczuk