[Matplotlib-users] On GtkAgg, one draw bad, two draws good?

[Alejandro Dubrovsky]

Hi,

I've run into something that I expect to be ground well covered but I
can't find anything relevant on google.

I'm on linux. When using the GtkAgg backend on matplotlib 1.1.0 (or git
head for that matter), with interactive mode on, one call to draw() only
gives me a blank window, while a second draw() immediately afterwards
will draw the requested graph. On IRC, askewchan told me it only one
draw is required under MacOSX, and it also works fine with just one draw
call if I switch to the TkAgg backend.

The following short script should demonstrate the issue (note: this is
only a problem when run as a script. It works fine on ipython, or
standard python prompt):

---
import time
from matplotlib import pyplot as plt

def graph():

plt.ion()

plt.plot(range(10), range(10,20))
plt.draw()
plt.draw()  # blank screen if this omitted
time.sleep(2)
plt.plot(range(30,40), range(10,20))
plt.draw()
plt.draw()  # second line not drawn if this omitted
time.sleep(2)

plt.ioff()

graph()
---

backend GTKAgg version 2.24.0
As a different but most likely related issue, th Qt4Agg backend doesn't
work even with two draw calls.

Is this a known issue? Is the script not using matplotlib as expected?
If so, is running a separate thread the intended way of showing graphs
in a non-blocking way?

Thanks,
alejandro

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Re: [Matplotlib-users] On GtkAgg, one draw bad, two draws good?

[Eric Firing]

On 02/25/2012 03:54 AM, Alejandro Dubrovsky wrote:
> Hi,
>
> I've run into something that I expect to be ground well covered but I
> can't find anything relevant on google.
>
> I'm on linux. When using the GtkAgg backend on matplotlib 1.1.0 (or git
> head for that matter), with interactive mode on, one call to draw() only
> gives me a blank window, while a second draw() immediately afterwards
> will draw the requested graph. On IRC, askewchan told me it only one
> draw is required under MacOSX, and it also works fine with just one draw
> call if I switch to the TkAgg backend.

This does not have a simple answer.  The basic problem is a collision 
between event-driven programming (the gui toolkit) and nice, simple 
sequential programming such as in your script.  The plotting commands 
essentially register requests with the gui toolkit, and the toolkit 
executes them when it gets around to it.  It won't do it during a 
time.sleep().  Typically, it has to be waiting for input, because that 
is when the mainloop is checking to see if there is anything that needs 
to be done.

>
> The following short script should demonstrate the issue (note: this is
> only a problem when run as a script. It works fine on ipython, or
> standard python prompt):
>

Try removing *all* your "draw" commands, and replace the calls to 
time.sleep(2) with plt.pause(2).  That works for me on gtkagg, qt4agg, 
wxagg, and tkagg. plt.pause() calls the event loop while waiting, 
instead of just freezing everything like sleep() does.

Eric

> ---
> import time
> from matplotlib import pyplot as plt
>
> def graph():
>
>   plt.ion()
>
>   plt.plot(range(10), range(10,20))
>   plt.draw()
>   plt.draw()  # blank screen if this omitted
>   time.sleep(2)
>   plt.plot(range(30,40), range(10,20))
>   plt.draw()
>   plt.draw()  # second line not drawn if this omitted
>   time.sleep(2)
>
>   plt.ioff()
>
> graph()
> ---
>
> backend GTKAgg version 2.24.0
> As a different but most likely related issue, th Qt4Agg backend doesn't
> work even with two draw calls.
>
> Is this a known issue? Is the script not using matplotlib as expected?
> If so, is running a separate thread the intended way of showing graphs
> in a non-blocking way?
>
> Thanks,
> alejandro
>
> --
> Virtualization&  Cloud Management Using Capacity Planning
> Cloud computing makes use of virtualization - but cloud computing
> also focuses on allowing computing to be delivered as a service.
> http://www.accelacomm.com/jaw/sfnl/114/51521223/
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Re: [Matplotlib-users] a venn diagram function written in python

[Benjamin Root]

On Friday, February 24, 2012, fdu.xia...@gmail.com wrote:

> Dear Ben Root,
>
> I have made a pull request of matplotlib on github, and I put my venn
> function on https://github.com/icetime/**matplotlib/blob/master/lib/**
> matplotlib/venn.py.
> However, I'm not sure it is the right place venn.py should go.
>
> This is my first time try to contribute to an open source project. Could
> someone please help review the code? Any comments will be greatly
> appreciated.Thanks.
>
> Regards,
> Jianfeng
>
>
>
Jianfeng,

A common mistake new contributors make is that they make a pull request
against their own mpl fork rather than the official one.  We have not
received your request yet.  You might want to try again.

Git is confusing at first, but once you try it out a bit more, it becomes
much easier to use.

Ben Root
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Re: [Matplotlib-users] a venn diagram function written in python

[Eric Firing]

On 02/25/2012 10:02 AM, Benjamin Root wrote:
>
>
> On Friday, February 24, 2012, fdu.xia...@gmail.com
>  wrote:
>
> Dear Ben Root,
>
> I have made a pull request of matplotlib on github, and I put my
> venn function on
> 
> https://github.com/icetime/__matplotlib/blob/master/lib/__matplotlib/venn.py
> 
> .
> However, I'm not sure it is the right place venn.py should go.
>
> This is my first time try to contribute to an open source project.
> Could someone please help review the code? Any comments will be
> greatly appreciated.Thanks.
>
> Regards,
> Jianfeng
>
>
>
> Jianfeng,
>
> A common mistake new contributors make is that they make a pull request
> against their own mpl fork rather than the official one.  We have not
> received your request yet.  You might want to try again.
>
> Git is confusing at first, but once you try it out a bit more, it
> becomes much easier to use.
>
> Ben Root
>
Ben,

A first cut would be an answer to the question as to where it belongs: 
mpl core? examples? cookbook?

I don't think it is of sufficiently general usefulness to belong in the 
core, so I think it would be better as an example.  What do you think?

Eric

>
>
> --
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> Cloud computing makes use of virtualization - but cloud computing
> also focuses on allowing computing to be delivered as a service.
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>
>
>
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Re: [Matplotlib-users] On GtkAgg, one draw bad, two draws good?

[Alejandro Dubrovsky]

On 02/26/12 06:25, Eric Firing wrote:
> On 02/25/2012 03:54 AM, Alejandro Dubrovsky wrote:
>> Hi,
>>
>> I've run into something that I expect to be ground well covered but I
>> can't find anything relevant on google.
>>
>> I'm on linux. When using the GtkAgg backend on matplotlib 1.1.0 (or git
>> head for that matter), with interactive mode on, one call to draw() only
>> gives me a blank window, while a second draw() immediately afterwards
>> will draw the requested graph. On IRC, askewchan told me it only one
>> draw is required under MacOSX, and it also works fine with just one draw
>> call if I switch to the TkAgg backend.
> 
> This does not have a simple answer.  The basic problem is a collision 
> between event-driven programming (the gui toolkit) and nice, simple 
> sequential programming such as in your script.  The plotting commands 
> essentially register requests with the gui toolkit, and the toolkit 
> executes them when it gets around to it.  It won't do it during a 
> time.sleep().  Typically, it has to be waiting for input, because that 
> is when the mainloop is checking to see if there is anything that needs 
> to be done.
> 
Ah, good explanation.

>>
>> The following short script should demonstrate the issue (note: this is
>> only a problem when run as a script. It works fine on ipython, or
>> standard python prompt):
>>
> 
> Try removing *all* your "draw" commands, and replace the calls to 
> time.sleep(2) with plt.pause(2).  That works for me on gtkagg, qt4agg, 
> wxagg, and tkagg. plt.pause() calls the event loop while waiting, 
> instead of just freezing everything like sleep() does.
> 
Yes, that works here too. It works even in non-interactive mode. Thank you.

I tried replacing all the draws in my program with plt.pause(0.01), and
it worked fine on GtkAgg, but when I tried it in QtAgg, it went to blank
screen mode. But upping it to 0.05 worked on both. So I went trawling
through code.

pause, through some intermediaries, seems to call flush_events, which
does the interfacing to the corresponding toolkit telling it to process
events, and then calls time.sleep for 0.01 seconds.  It does this until
the total slept time matches or exceeds what you specify.  And it seems
that Qt needs two separate rounds to get everything done. So a call like
plt.pause(0.015) works well

The time.sleep calls from pause seem unnecessary for the people like me
that just want to use pause as a get events processed signals.  It would
be good if flush_events had a direct interface.

(writing this so that maybe it gets picked up by a search engine)

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