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Sonnich
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 Posted: Thu Jan 05, 2006 12:50 pm Post subject: Win32 error 1400 - invalid handle with TPanel |
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Hi all!
I have a component based on TCustomChart, which a few components on it.
A TPanel causes this error.
The panel is default invisible, create as:
pnl1 := TPanel.Create(self);
pnl1.Parent := Self;
pnl1.BringToFront;
pnl1.BevelInner := bvNone;
pnl1.BevelOuter := bvNone;
pnl1.Color := Legend.Color;
pnl1.Visible := False;
This causes the error when the app is being closed.
Simply, by removing the "visible = false" and I avoid the problem.
Can anyone explain?
How do I create a panel, which is disabled?
/Sonnich
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alanglloyd@aol.com
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| Posted: Sat Jan 07, 2006 5:59 am Post subject: Re: Win32 error 1400 - invalid handle with TPanel |
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Check that the panel has a window handle for your interest ...
if not Pnl1.HandleAllocated then
ShowMessage('Pnl1 does not have a Handle);
.... and ensure that it does have a handle by calling ...
Pnl1.HandleNeeded;
I don't know why the handle is not created (if that is the case) but
this may be the problem. Maybe if the window is not visible then no
handle is allocated.
Do you specifically Free the panel before closing the app. You should
because you have created it.
Alan Lloyd
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Maarten Wiltink
Guest
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| Posted: Sat Jan 07, 2006 1:45 pm Post subject: Re: Win32 error 1400 - invalid handle with TPanel |
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<alanglloyd (AT) aol (DOT) com> wrote
[...]
| Quote: | Do you specifically Free the panel before closing the app. You should
because you have created it.
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This is a good rule in general, but TComponent (from which TPanel
derives) does have infrastructure in place to have another component
free it: the Owner property and parameter to Create.
Groetjes,
Maarten Wiltink
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Sonnich
Guest
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| Posted: Thu Jan 12, 2006 8:41 am Post subject: Re: Win32 error 1400 - invalid handle with TPanel |
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Well, I found the problem.
I call a function from another thread, which enables the panel if
needed, something like:
procedure SetMyPanel(somevar: boolean);
mypanel.visible := somevar;
But when calling this from a thread, it fails. Seems like the "true"
set from there is related to thre thread.
So instead from the thread I do so:
otherclass.somevar := true;
sync...(somefunc)
procedure somefunc;
mypanel.visible := somevar;
then it works.
The point is, that the thread is a one-shot. It terminates rigth after
doing this.
S
Maarten Wiltink wrote:
| Quote: | alanglloyd (AT) aol (DOT) com> wrote in message
news:1136613557.135981.261760 (AT) g47g2000cwa (DOT) googlegroups.com...
[...]
Do you specifically Free the panel before closing the app. You should
because you have created it.
This is a good rule in general, but TComponent (from which TPanel
derives) does have infrastructure in place to have another component
free it: the Owner property and parameter to Create.
Groetjes,
Maarten Wiltink
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Nicholas Sherlock
Guest
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| Posted: Thu Jan 12, 2006 7:13 pm Post subject: Re: Win32 error 1400 - invalid handle with TPanel |
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Sonnich wrote:
| Quote: | Well, I found the problem.
I call a function from another thread, which enables the panel if
needed, something like:
procedure SetMyPanel(somevar: boolean);
mypanel.visible := somevar;
But when calling this from a thread, it fails. Seems like the "true"
set from there is related to thre thread.
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Danger, Will Robinson! Danger!
You cannot access the VCL from outside the main thread. It is not thread
safe. Use synchronize or a similar solution.
Cheers,
Nicholas Sherlock
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