"BackgroundWorker" in BlitzMax

BlitzMax Forums/MaxGUI Module/"BackgroundWorker" in BlitzMax

Marcell

(Posted 2014) [#1]

Hello,
in Visual Studio there's BackgroundWorker class for time consuming tasks. How this should be done in BlitzMax?

I would like to have stop button that can be used to stop the time consuming task.

ziggy

(Posted 2014) [#2]

There was a worker-like implementation in the threading module if I'm right

Marcell

(Posted 2014) [#3]

Could someone help me out. The following seems to be wrong way of doing it:

thread:TThread = CreateThread (Test, Null)

While ThreadRunning (thread)
	If KeyHit(KEY_ESCAPE) Then DetachThread(thread)
	Delay 1
Wend
End

Function Test:Object (data:Object)
	Repeat	
		i = i + 1
		Print i
	Until i = 1000000
End Function

(remember to check "Threaded Build" from the IDE)

col	(Posted 2014) [#4]

Hey,

The correct way to do what you want is to have a thread messaging system to allow threads to communicate. In the worker thread you'd poll for messages while doing the heavy work. In the main app you could then send a message to the thread to stop what it is doing and exit. Don't ever try to 'kill' threads, always let the exit correctly.

Now that would the 'correct way' of doing things ;-)

On the other hand you could throw together something that uses an atomic variable and switch it using the correct atomic functions, but this isn't scalable and would only be any good for its single purpose. I don't endorse this kind of multithread code but hey... if nothing else, it serves as a learning aid for you :^)

Strict
Global ExitThreadNow:Int = False

Local thread:TThread = CreateThread (Test, Null) 

' switch on polledinput for keypresses - otherwise key presses go to the console in the IDE
' might not need this in a real background app.
Graphics 200,200 ' DEMO PURPOSES ONLY

While ThreadRunning (thread)
	If KeyHit(KEY_ESCAPE) Then AtomicSwap(ExitThreadNow,True)
	Delay 1
Wend
Print "App exiting"
End

Function Test:Object (data:Object)
	Local CarryOnWorking:Int = True
	Repeat
		Print "Working...."
		If CompareAndSwap(CarryOnWorking,ExitThreadNow,False)
			Exit
		EndIf
	Forever
	Print "Thread exited"
End Function

Marcell

(Posted 2014) [#5]

Thanks! I haven't done much in BlitzMax yet. This was my first try to use threads.

Marcell

(Posted 2014) [#6]

About the stop button... In Visual Studio button's appearence changes, if the button is disabled. In BlitzMax (MaxGUI) disabled button (TGadget) looks the same as enabled button. What's the usual way to handle this?

Should I install some other module for this purpose? Which?

col	(Posted 2014) [#7]

Strict
Import maxgui.drivers

Local win:TGadget = CreateWindow("Test",0,0,300,300)
Local button:TGadget = CreateButton("STOP",20,20,120,20,win)
DisableGadget(button)

Repeat
	WaitEvent
	Local ev:TEvent = CurrentEvent
	
	Select ev.id
	Case EVENT_WINDOWCLOSE
		Exit
	EndSelect
Forever

Yes DisableGadget and EnableGadget are the correct functions. This code shows a disabled button gadget for me. It changes the visual look ( fades the border and text ) to show that it's disabled.

As a side note, I notice that you didn't use Strict or SuperStrict in your code. I've not sure if you are in your real code ( as opposed to not when posting snippets to the forum ), but my advise is to always use at least Strict. It will help catch any typos in your code that, without the use of some kind of 'strictness', will still compile and run but could contain bugs.

Marcell

(Posted 2014) [#8]

I must have been blind, because I didn't notice this myself. Perhaps I should use my glasses more often... :-)