I'm creating a game with some AI that may take some time. The problem is even if I call relevant methods to update the UI before running the AI function, the UI is not visually updated.
Some example code looks like this
def onClickBoard(self, e):
x, y = toBoardGrid(e.x(), e.y())
self.game.move(x, y)
self.update_board()
print("before AI")
# This line takes a few seconds
ai_move = self.ai.get_best_move(self.game)
print("after AI")
self.game.move(ai_move[0], ai_move[1])
self.update_board()
Where self.update_board is a method that updates a QWidget and it's very fast. This onClickBoard method is assigned to the widget's mouseReleaseEvent.
self.board.mouseReleaseEvent = self.onClickBoard
When running the game, I can see before AI printed to the terminal but the visual window doesn't change. I see the window updates only once, after the AI commits its move.
Is there a way to make the board update once before the slow function call and another once after it?
Yes, you can force Qt to process all pending events, and thus update the GUI, with the QApplication::processEvents() method. Add the following line just before the slow function call:
QtWidgets.QApplication.instance().processEvents()
Related
Here's what the click event currently looks like for the ListBox in the dialog code.
def OnSelectCategory(self, listbox, data=None):
try:
# Get the text of the selected category.
selected = listbox.get_selected_row()
label = selected.get_child()
itemText = label.get_text()
# Get the tags for the selected category.
tagtext = self.categoryTags.get(itemText)
self.updateStatusbar("Collecting videos...")
# Start a thread to scan for videos.
self.threadEvent = threading.Event()
self.videoscanThread = threading.Thread(target=self.ScanForVideos, args=(self.threadEvent, tagtext,))
self.videoscanThread.daemon = True
self.videoscanThread.start()
self.threadEvent.set()
except Exception as e:
print("Exception from 'OnSelectCategory':", str(e))
At first, I could not get the status bar to update the text immediately. I had originally called the function to update the text directly. The status bar text would not update until the ScanForVideos function had finished. So, I moved the ScanForVideos code into a thread. The thread waits on an event to begin.
The thread (ScanForVideos) runs several 'for' loops looking for a matching condition. When the condition is found, the code appends to the liststore for the IconView. At the end of the thread function, the code sets the IconView model to the liststore. The IconView seems to update with a few items, but, not all that should be there. Additionally, the code seems to be 'hung' because I cannot dismiss the dialog that contains the IconView. I have to stop debugging within Visual Studio Code.
I feel like I'm violating something I'm not aware of in Python coding. Or, my design to update the IconView is not correct. Can anyone shed some light on what I may be doing wrong?
I realized that I was trying to update some UI widgets from within my background thread. I then stumbled upon GLib.idle_add. I wrote a separate function to update the UI widgets and called idle_add passing the name of the function. This allowed me to update the GUI from a background thread.
I started with some code like this which connects a function to a GUI button.
def on_click():
call_other_funct()
time.sleep(1)
button = QPushButton('Do the thing', self)
button.pressed.connect(on_click)
The problem is I need to repeatedly call on_click() every second for the duration of the mouse being held down on the button. I've searched quite a bit but haven't found a solution using PyQt.
I've been trying to fix this using a timer interval
def on_release():
self.timer.stop()
def on_click():
self.timer.start(1000)
self.timer.timeout.connect(on_click())
print('click')
button.pressed.connect(on_click)
button.released.connect(on_release)
This sort of works, but for some reason there seem to be and exponential number of on_click() calls happening. (on the first call, "click" prints once, then twice, then 4 times, then 8 etc). Is there a way to make this work correctly so each call only calls itself again once?
Or is there an all together better way to be doing this?
I suspect that the "exponential growth" comes from the fact that in the event handler on_click, you create a connection between the timer and the event handler itself. So I would expect something like this to happen:
on_click is executed once and the timer is connected once to on_click
after a second, the timer runs out and triggers on_click. During execution of on_click, the timer is connected to on_click again.
after a second, the timer runs out and triggers on_click twice (due to 2 connections). Which in turn then generate 2 more connections.
etc.
What you should do is connect your timer to another function which actually does the thing you want to execute every second while the mouse button is down.
def on_release():
self.timer.stop()
def on_press():
self.timer.start(1000)
def every_second_while_pressed():
print('click')
button.pressed.connect(on_press)
button.released.connect(on_release)
self.timer.timeout.connect(every_second_while_pressed)
I have an expensive function that is called via a Tkinter callback:
def func: # called whenever there is a mouse press in the screen.
print("Busy? " + str(X.busy)) # X.busy is my own varaible and is initialized False.
X.busy = True
do_calculations() # do_calculations contains several tk.Canvas().update() calls
X.busy = False
When I click too quickly, the func()'s appear to pile up because the print gives "Busy? True", indicating that the function hasen't finished yet and we are starting it on another thread.
However, print(threading.current_thread()) always gives <_MainThread(MainThread, started 123...)>, the 123... is always the same each print for a given program run. How can the same thread be multiple threads?
It looks to me like you're running into recursive message processing. In particular, tk.Canvas().update() will process any pending messages, including extra button clicks. Further, it will do this on the same thread (at least on Windows).
So your thread ID is constant, but your stack trace will have multiple nested calls to func.
I am writing a tool in python 2.7 registering the amount of times the user pressed a keyboard or mouse button. The amount of clicks will be displayed in a small black box in the top left of the screen. The program registers clicks even when another application is the active one.
It works fine except when I move the mouse over the box. The mouse then freezes for a few seconds after which the program works again. If I then move the mouse over the box a second time, the mouse freezes again, but this time the program crashes.
I have tried commenting out pumpMessages() and then the program works. The problem looks a lot like this question pyhook+tkinter=crash, but no solution was given there.
Other answers has shown that there is a bug with the dll files when using wx and pyhook together in python 2.6. I don't know if that is relevant here.
My own thoughts is that it might have something to do with the two event loops running parallel. I have read that tkinter isn't thread safe, but I can't see how I can make this program run in a single thread since I need to have both pumpmessages() and mainlooop() running.
To sum it up: Why does my program freeze on mouse over?
import pythoncom, pyHook, time, ctypes, sys
from Tkinter import *
from threading import Thread
print 'Welcome to APMtool. To exit the program press delete'
## Creating input hooks
#the function called when a MouseAllButtonsUp event is called
def OnMouseUpEvent(event):
global clicks
clicks+=1
updateCounter()
return True
#the function called when a KeyUp event is called
def OnKeyUpEvent(event):
global clicks
clicks+=1
updateCounter()
if (event.KeyID == 46):
killProgram()
return True
hm = pyHook.HookManager()# create a hook manager
# watch for mouseUp and keyUp events
hm.SubscribeMouseAllButtonsUp(OnMouseUpEvent)
hm.SubscribeKeyUp(OnKeyUpEvent)
clicks = 0
hm.HookMouse()# set the hook
hm.HookKeyboard()
## Creating the window
root = Tk()
label = Label(root,text='something',background='black',foreground='grey')
label.pack(pady=0) #no space around the label
root.wm_attributes("-topmost", 1) #alway the top window
root.overrideredirect(1) #removes the 'Windows 7' box around the label
## starting a new thread to run pumMessages() and mainloop() simultaniusly
def startRootThread():
root.mainloop()
def updateCounter():
label.configure(text=clicks)
def killProgram():
ctypes.windll.user32.PostQuitMessage(0) # stops pumpMessages
root.destroy() #stops the root widget
rootThread.join()
print 'rootThread stopped'
rootThread = Thread(target=startRootThread)
rootThread.start()
pythoncom.PumpMessages() #pump messages is a infinite loop waiting for events
print 'PumpMessages stopped'
I've solved this problem with multiprocessing:
the main process handles the GUI (MainThread) and a thread that consumes messages from the second process
a child process hooks all mouse/keyboard events and pushes them to the main process (via a Queue object)
From the information that Tkinter needs to run in the main thread and not be called outside this thred, I found a solution:
My problem was that both PumpMessages and mainLoop needed to run in the main thread. In order to both receive inputs and show a Tkinter label with the amount of clicks I need to switch between running pumpMessages and briefly running mainLoop to update the display.
To make mainLoop() quit itself I used:
after(100,root.quit()) #root is the name of the Tk()
mainLoop()
so after 100 milliseconds root calls it's quit method and breaks out of its own main loop
To break out of pumpMessages I first found the pointer to the main thread:
mainThreadId = win32api.GetCurrentThreadId()
I then used a new thread that sends the WM_QUIT to the main thread (note PostQuitMessage(0) only works if it is called in the main thread):
win32api.PostThreadMessage(mainThreadId, win32con.WM_QUIT, 0, 0)
It was then possible to create a while loop which changed between pumpMessages and mainLoop, updating the labeltext in between. After the two event loops aren't running simultaneously anymore, I have had no problems:
def startTimerThread():
while True:
win32api.PostThreadMessage(mainThreadId, win32con.WM_QUIT, 0, 0)
time.sleep(1)
mainThreadId = win32api.GetCurrentThreadId()
timerThread = Thread(target=startTimerThread)
timerThread.start()
while programRunning:
label.configure(text=clicks)
root.after(100,root.quit)
root.mainloop()
pythoncom.PumpMessages()
Thank you to Bryan Oakley for information about Tkinter and Boaz Yaniv for providing the information needed to stop pumpMessages() from a subthread
Tkinter isn't designed to be run from any thread other than the main one. It might help to put the GUI in the main thread and put the call to PumpMessages in a separate thread. Though you have to be careful and not call any Tkinter functions from the other thread (except perhaps event_generate).
I have a MATLAB GUI and a separate application that writes data to a file.
I'd like my MATLAB GUI to check the file periodically, and update the GUI when it changes.
In Java, I'd use a SwingUtils.Timer(sp?) object to do something like this. Does MATLAB have timer functionality? I could write a java class and do it I suppose, but want something quick and dirty for a demo, preferably pure MATLAB.
You can create timer objects in MATLAB using the TIMER function. For example, this creates a timer object which should execute the function myFcn once every 10 seconds after the timer is started:
timerObject = timer('TimerFcn',#myFcn,'ExecutionMode','fixedRate',...
'Period',10.0);
Timers are started and stopped using the functions START and STOP. You should also always remember to delete them with DELETE when you're done using them. You can find more info on using timers in the MATLAB documentation.
It is worth noting, that if you are wanting to update axes object in a GUIDE GUI, there's an additional bit of "trickery" needed to make this work. You must either change the HandleVisibility property of the axes object in GUIDE, or you must explicitly acquire the handle. To do this, change the timerObject construction as follows (This is assuming the axes window in your GUIDE generated GUI is called axes1):
timerData.axes = handles.axes1;
timerData.n = 1; % some state needed for the plots.
timerObject = timer('TimerFcn',#myFcn,...
'ExecutionMode','fixedRate',...
'Period',10.0,...
'UserData', timerData);
then in myFcn, we need to reference the axes object. Specifically:
function [] = myFcn(timerObj, event)
timerData = get(timerObj, 'UserData');
plot(timerData.axes, (1:n)/n, sin(20*2*pi*(1:n)/n));
line( (1:n)/n, cos(20*2*pi*(1:n)/n, 'Parent', timerData.axes);
timerData.n = timerData.n + 1;
set(timerObj, 'UserData', timerData);
end