Is there a limit to amount of controls.
lazarus / 39-Graphics

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Josh · 2015-03-18 20:47

I am creating a app that has many controls in it, in access of 5000.
These controls are on numerous panels and everything, the controls
only get updated if they are visible.
The problem I have is that I have a panel that has approx 500 controls
on which are tbcbuttons, ( simulating 5 piano keyboards using
tbcbuttons as keys so I can add text to the keys). These are created
on application create event, the problem I get is when I try make this
panel visible I get an Ememory error.
If I reduce the piano keyboards to 3, then the panel shows fine, if I
set to 4 more often than not will not show, If I set to 5 it error as
soon as I set the panel visible.
So I am wondering if the amount of controls on a panel has a limit, or
does the application have a limit.
I do have some large arrays that I have now set to dynamic so they are
on the heap, thinking maybe the stack is getting full.
Wondering if anyone has come up with this problem.
WHen I create controls programatically ( as approx 4500 are created
this way) is the info for this control in the stack or heap, done a
bit of googling but couldn't find a answer.

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Never · 2015-03-18 21:22

new classes objects etc are alive in the heap
about your problem : on every system there are other apps running
exept yours so with this amount of controls is just a matter of time
to reach  memory limits
to overcome this slpit the gui to what a humman can read and create
and display what is required only when is required and unload it when
you are done with it.

even thought i'm not aware about your app
it might be a good idea to consider
 using picture for your piano displays labels to set captions and
create a frame with your buttons and set this frame over each image
when ever you need inderaction  from the user

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Basile B. · 2015-03-18 23:22

it's easy to test by yourself until you realize that the limit is the
physical memory (maybe some weird things can also happend with GDI
handles under win):

Code: [Select]procedure TForm1.Test;
var
  Ctrl: TPanel;
  i : Uint64;
begin
  while (true) do begin
    try
      Ctrl := TPanel.Create(self);
      Ctrl.parent := self;
      i += 1;
   except
      // i indicates the possible amount of ctrl on this system...
      break;
    end;
      if i = high(Uint64) then
        break;  
  end;
end;

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Josh · 2015-03-18 23:39

Hi Thanks for your responses.
@Never
I think I may have to try creating the controls before I show the
Panels and see if that helps.
@Basile B
I done a similar test, and created way more than I was using across
multiple panels. The problem is odd in that the panel is created with
the controls on successfully, no errors. A soon as I set that panel to
visible the error occur, I do not even see the panel appear.

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Mike.Cornflake · 2015-03-19 01:11

Quote from: josh on March 19, 2015, 12:39:46 amA soon as I set that
panel to visible the error occur, I do not even see the panel appear.

If the problem is simply panels 4 and above not being visible, then I
think we will need to see code.

If your whole PC wobbles (and maybe even crashes) when you show panel
4 and above, then you have exceeded the Windows GDI Count, and Windows
*STILL* can't handle that (pun intended). I think the Max GDI count
for modern windows is 10,000.

I have problems with GDI Count in my own app - I know the solution to
my particular issue - don't have a TImageList with 100+ small icons in
it in a base form.  If exceeding 10000 GDI objects is indeed your
problem, then the only solution is to NOT exceed the GDI count :-) 

You can add GDI Objects as a column in Task Manager - find your app,
see what the GDI Object count is.  If it's low, this isn't your
problem...

Update:  New limit could be 16K, not 10K
https://msdn.microsoft.com/en-
us/library/windows/desktop/ms724291%28v=vs.85%29.aspx

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Basile B. · 2015-03-19 01:32

Quote from: josh on March 19, 2015, 12:39:46 amHi Thanks for your
responses.
@Never
I think I may have to try creating the controls before I show the
Panels and see if that helps.
@Basile B
I done a similar test, and created way more than I was using across
multiple panels. The problem is odd in that the panel is created with
the controls on successfully, no errors. A soon as I set that panel to
visible the error occur, I do not even see the panel appear.

With my example you'll necessarily have something like an OutOfMemory
error, even on a 64 bit system, this will allocate up to
$FFFFFFFFFFFFFFFF * TPanel.instanceSize bytes which exceeds the
maximum memory a 64 bit OS is able to manage (2^64).

And it supposes that the same amount of DRAM would be setup...what it
this amount nowadays ? 32 GB in the better cases ? Even each byte of a
the biggest hard drive of the market can be indexed in a Uint64...