Multithreaded filter exception

[lainz]

Hi, I'm trying to create a multithreaded filter with BGRABitmap.

For testing purpouses I'm implementing a simple grayscale filter with 2 threads.

https://github.com/bgrabitmap/multithreadedfilter

It works, but the problem I have is that I get an exception when I resize the form a lot of times

This is the algorithm unit
https://github.com/bgrabitmap/multithreadedfilter/blob/master/umultithreadfilter.pas

Code: Pascal  [Select][+][-]

1. arr[i] := TThreadFilter.Create(True);

Attached the exception dialog.

In English is something like:

"There are not enough memory resources to process this command".

[MarkMLl]

Check that your thread's code isn't trying to manipulate the GUI directly (you need to use Synchronize()). If you've got custom code drawing to e.g. a canvas, check that it's all in the repaint handler since otherwise it will go recursive.

MarkMLl

[lainz]

I added

Code: Pascal  [Select][+][-]

1.   repeat
2.     AllFinished := True;
3.     for j := Low(arr) to High(arr) do
4.       if arr[j] <> nil then
5.         if not arr[j].AFinished then
6.           AllFinished := False;
7.   until AllFinished;

And now it works, but the main form is a bit slower... since the repeat is being executed in the main thread, so I lost the "visible" speed gain...

Code: Pascal  [Select][+][-]

1. {for j:=Low(arr) to High(arr) do
2.     arr[i].WaitFor;}

For some reason .WaitFor doesn't works, and the main form is never repainted.

[lainz]

I fixed the 'WaitFor' issue 

The problem was that I was calling Execute instead of Start. Now it works properly.

With 2 threads the code works nicely.

[circular]

Well done!