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Unload CEF without shutting down the program?
Posted: Tue May 19, 2020 12:58 pm
by parlavamba
Hi,
I am trying to use CEF4Delphi 81.2.16+chromium-81.0.4044.92 in my DLL with modal form and have encountered a problem.
I need to load the SEF at the beginning of working with the DLL and unload the CEF before unloading my DLL. Loading and unloading takes place inside my DLL.
I added
, but CEF is not unloaded, and AV occurs when the form is run again, since
cannot start.
I did an experiment in the DLLBrowser demo - added
Code: Select all
GlobalCEFApp.MustFreeLibrary := True
before
, but when I run "3. Finalize", I get the AV a few seconds after unloading the CEF.
How can I load and unload CEF correctly without shutting down the program?
Please help me.
Re: Unload CEF without shutting down the program?
Posted: Wed May 20, 2020 8:27 am
by salvadordf
Hi,
There are a few of things you have to consider when using a DLL with CEF :
If the code in the DLLBrowser demo works for your application I would recommend that you copy it.
Re: Unload CEF without shutting down the program?
Posted: Wed May 20, 2020 10:00 am
by parlavamba
Hi, thank you for your answer.
I'll try to explain in more detail:
There is an application that the DLLs connect to. But there is no source code for this app, it is closed.
I can only work with a DLL, and I need to use chromium in my DLL, that is, both initialize and release chromium inside the DLL.
My DLL can run from this application several times, so I need to release the CEF each time and initialize it again without closing the application.
Is it impossible to do this?
I just need to completely unload the CEF so that the next time I run my DLL from the app, it can be re-initialized.
Re: Unload CEF without shutting down the program?
Posted: Wed May 20, 2020 10:11 am
by parlavamba
Maybe there is some way to kill all the remaining CEF threads to release "libcef.dll" ?
Then "GlobalCEFApp.StartMainProcess" can be executed again without errors.
Re: Unload CEF without shutting down the program?
Posted: Wed May 20, 2020 10:23 am
by parlavamba
This is how the DLL is called, the application calls the Delivery Address function:
Code: Select all
procedure DeliveryAddress(AOwner: TComponent; ACallBack: TDLLCallBack);
begin
try
CreateGlobalCEFApp;
DM := TDM.CreateDM(nil, ACallBack);
DeliveryAddressForm := TDeliveryAddressForm.Create(nil);
try
DeliveryAddressForm.ShowModal;
finally
DeliveryAddressForm.Free;
DM.Free;
Application.Handle := 0;
DestroyGlobalCEFApp;
end;
except
on E:Exception do
MessageBox(Application.Handle, PWideChar(E.ClassName + ' - ' + E.Message), 'Error!', 0);
end;
end;
procedure CreateGlobalCEFApp;
var
LLibPath: string;
begin
LLibPath := ExtractFilePath(paramstr(0)) + 'Lib\';
GlobalCEFApp := TCefApplication.Create;
GlobalCEFApp.FrameworkDirPath := LLibPath;
GlobalCEFApp.ResourcesDirPath := LLibPath;
GlobalCEFApp.Cache := LLibPath + 'cache';
GlobalCEFApp.UserDataPath := LLibPath + 'userData';
GlobalCEFApp.LocalesDirPath := LLibPath + 'locales';
GlobalCEFApp.BrowserSubprocessPath := LLibPath + 'SubProcess.exe';
GlobalCEFApp.MustFreeLibrary := True;
GlobalCEFApp.StartMainProcess;
end;
After closing the form and starting again, an AV error appears on "GlobalCEFApp.StartMainProcess" with the message "libceff.dll busy with another process."
Re: Unload CEF without shutting down the program?
Posted: Wed May 20, 2020 10:24 am
by salvadordf
As far as I know, CEF doesn't allow you to initialize it several times in the same process. This is a CEF feature and there's no workaround.
I thought that was an unbreakable CEF rule until I saw the exception I commented earlier but I would try to use CEF as suggested by the CEF maintainer.
However, if you make some tests and find more exceptions to this rule, please let us know!
If you follow the official recommendations then you would have to create a separate application with the CEF browser. Then use some form of Inter-process communication (IPC) to send and receive commands and information from your DLL to the new application like this :
Code: Select all
Main app <---> your DLL <--(IPC)--> The new CEF browser App
This way you would launch and close the new CEF browser app each time your DLL is loaded/unloaded.
Re: Unload CEF without shutting down the program?
Posted: Wed May 20, 2020 10:32 am
by parlavamba
This is very sad
.
Thank you for your help, kind man.