Moving a window on the screen

[Terry Reedy]

On 11/8/2014 11:35 AM, Akira Li wrote:
> "ast" <nomail at invalid.com> writes:
>
>> Ok, thx, it works now with:
>>
>> import tkinter
>> fen = tkinter.Tk()
>>
>> x=0
>>
>> def moveW():
>>     global x
>>     fen.geometry("200x200+%d+10"  %  x)
>>     x = x + 10
>>     if (x < 1200):
>>         fen.after(50, moveW)
>>
>> moveW()
>
> In general, to avoid the start time "drift" [1],

which is hardly noticeable

> you could lock the
> execution with a timer e.g., to move the window from left to right
> *delta_x* pixels at a time every *period* ms [2]:

On my Win7 machine, your complicated code is much worse as it causes the 
window to jump about every half second

>    #!/usr/bin/env python3
>    from time import monotonic
>    from tkinter import Tk
>
>    def timer():
>        return int(monotonic() * 1000) # milliseconds
>
>    def call_repeatedly(period, function, *args):
>        root.after(period - timer() % period, call_repeatedly, period,

The '- timer() % period' 'correction' is wrong when not 0 as it causes 
jumps.

>                   function, *args) # schedule the next call
>        function(*args)
>
>    def move(delta_x, max_x, width=200, x=[0]):
>        root.geometry("%dx50+%d+100"  %  (width, x[0]))
>        x[0] += delta_x # poor man's object
>        if x[0] > (max_x - width):
>            root.destroy() # exit
>
>    root = Tk()
>    period = 20 # call every *period* milliseconds
>    delta_x = 2 # how many pixels to move at a time
>    root.after(period - period % timer(), call_repeatedly, period,

'period % timer()' is nonsensical as timer() is arbitrary. It will 
typically be 0 anyway.  'after(0, ...)'  works fine.

>               move, delta_x, root.winfo_screenwidth())
>    root.mainloop()
>
>
> [1]: http://stackoverflow.com/questions/8600161/executing-periodic-actions-in-python#comment26637231_8600301
> [2]: http://stackoverflow.com/questions/24174924/how-to-run-a-function-periodically-in-python
>
>
> Akira
>


-- 
Terry Jan Reedy