I wanted to try out a new idea about doing threads with pygtk.
While experimenting a bit it seems I stumbled upon a bug in
pygtk. I have a number of equivallent threads who all produce
some kind of result which they then put on a canvas.
The method they use is like this:
def Adjust(self, ThrdIx, Time, Value):
gdk.threads_enter()
Do some calculations and "painting"
gdk.flush()
gdk.threads_leave()
self.ThrdInfo[ThrdIx] = [Time, Value]
#end Adjust
If I run the program like this, it will crash after some time
with an Xlib Error. Most often a Xlib: unexpected async reply
but I also received an X Window System error.
However if I move the gdk.threads_leave() to the last line
the problem disappears. But moving that call to the last
line doesn't put any gtk or gdk call within the gdk.threads_enter
gdk.threads_leave pair so that shouldn't have an influence.
There is also no other thread that is running or any gtk or
gdk call somewhere else within the threads that are running.
So in my opinion this points to a bug in pygtk.
The complete program is here below, start it up and click
in the window, normally a crash occurs before the numbers
reach 300000.
I am working with a Debian testing system with a 2.4.27-2-686
kernel. libgtk 2.6.4-3, python 2.3.5-2, python-gtk2 2.6.2-1
-------------------------------------------------------------
import pygtk
pygtk.require('2.0')
import gtk
import gtk.gdk as gdk
import pango
from threading import Thread, Lock
from random import Random, randint, sample
from time import sleep, time
import os
import sys
pname = sys.argv[0].split(os.sep)[-1]
demo_id = pname.split('.')[0].replace("demo" , '')
def Connect(obj, signal, handler, *args):
def wrap(handler):
def wrapper(obj, *args):
gdk.threads_leave()
handler(obj, *args)
gdk.threads_enter()
#end wrapper
return wrapper
#end wrap
obj.connect(signal, wrap(handler), *args)
#end Connect
class Counting (Thread):
def __init__(self, Id):
self.Id = Id
self.ctrl = True
self.Running = False
self.ShowMode = 0
self.Time = 0
self.Value = 250
self.lock = Lock()
self.lock.acquire()
self.PRG = Random()
Thread.__init__(self)
#end __init__
def run(self):
def limit(x, sub, sup):
if x < sub:
return sub
elif x > sup:
return sup
else:
return x
#end if
#end limit
while 1:
if not self.Running:
self.lock.acquire()
#end if
if not self.ctrl:
return
#end if
OldTime = self.Time
self.Time = OldTime + self.PRG.randint(1,20)
while OldTime < self.Time:
OldTime += 1
#end while
self.Value = limit(self.Value + self.PRG.randint(-5,5) , 0 , 500)
canvas.Adjust(self.Id, self.Time , self.Value)
#end while
#end run
def Start_Stop(self,ignore):
if self.Running:
self.Running = False
else:
self.Running = True
self.lock.release()
#end if
#end Start_Stop
def Quit(self):
self.ctrl = False
if not self.Running:
self.Running = True
self.lock.release()
#end if
#end Quit
#end Counting
Worker = [ Counting(i) for i in xrange(7) ]
for W in sample(Worker,7):
W.start()
#end for
RowHght = 25
def index2rgb(ix, ColorScale = 3 * 65535 / 5):
return (ColorScale * (ix & 4) >> 2,
ColorScale * (ix & 2) >> 1,
ColorScale * (ix & 1) >> 0)
#end index2rgb
class Canvas(gtk.DrawingArea):
def __init__(self):
def On_Expose(canvas, evt):
gc = canvas.window.new_gc()
lb = canvas.window.new_gc()
cm = gc.get_colormap()
gdk.threads_enter()
for i in xrange(7):
color = cm.alloc_color(*index2rgb(i))
gc.set_foreground(color)
canvas.window.draw_rectangle(gc, True , 75, (2 * i + 1) * RowHght ,
canvas.ThrdInfo[i][1] , RowHght )
canvas.layout.set_text("%8d" % (canvas.ThrdInfo[i][0],))
canvas.window.draw_layout(lb, 5 , (2 * i + 1) * RowHght + canvas.TxtPad
, canvas.layout)
#end for
gdk.threads_leave()
#end On_Expose
gtk.DrawingArea.__init__(self)
self.add_events(gdk.BUTTON_PRESS_MASK)
self.set_size_request(600, 15 * RowHght)
self.layout = self.create_pango_layout("")
desc = self.layout.get_context().get_font_description()
desc.set_family("Monospace")
self.TxtPad = desc.get_size() / (2 * pango.SCALE)
self.ThrdInfo = [ [0 , 250 ][:] for x in range(7) ]
self.layout.set_font_description(desc)
Connect(self, "expose_event" , On_Expose)
Connect(self, "button_press_event" , self.On_Click)
#end __init__
def On_Click(self, evnt, info):
for W in sample(Worker,7):
W.Start_Stop(None)
#end for
#end On_Click
def Adjust(self, ThrdIx, Time, Value):
gdk.threads_enter()
gc = self.window.new_gc()
lb = self.window.new_gc()
cm = gc.get_colormap()
OldValue = self.ThrdInfo[ThrdIx][1]
if OldValue < Value:
color = cm.alloc_color(*index2rgb(ThrdIx))
base = 75 + OldValue
else:
color = self.style.bg[0]
base = 75 + Value
#end if
gc.set_foreground(color)
self.window.draw_rectangle(gc, True , base , (2 * ThrdIx + 1) * RowHght ,
abs(Value - OldValue) , RowHght)
self.layout.set_text("%8d" % (Time,))
self.window.begin_paint_rect((0, (2 * ThrdIx + 1) * RowHght, 75 , RowHght))
self.window.draw_layout(lb, 5 , (2 * ThrdIx + 1) * RowHght + self.TxtPad ,
self.layout)
self.window.end_paint()
gdk.flush()
gdk.threads_leave()
self.ThrdInfo[ThrdIx] = [Time, Value]
#end Adjust
#end Canvas
class Frame(gtk.Window):
def __init__(self,canvas):
gtk.Window.__init__(self, gtk.WINDOW_TOPLEVEL)
self.set_title("Thread %s Demonstration" % demo_id)
Connect(self, "delete_event" , self.On_Delete)
self.add(canvas)
canvas.show()
self.show()
#end __init__
def On_Delete(self, widget, evt, data=None):
for W in sample(Worker,7):
W.Quit()
#end for
for W in sample(Worker,7):
W.join()
#end for
gtk.main_quit()
return False
#end On_Delete
#end Frame
gtk.threads_init()
canvas=Canvas()
Win=Frame(canvas)
gtk.threads_enter()
gtk.main()
gtk.threads_leave()
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