Multiple EAs using single DLL with DLL Windows - Using Delphi

I've recently had a request from a member to show how to create a DLL with window(s) that is used by an EA rather than an indicator.

As mentioned before in other threads (and most people know) Indicators run in MT4s main application thread. This means that if you create non modal windows in your DLL they will work fine since the DLL windows messages will be processed by the MT4 main app.

EAs on the other hand, each run in their own thread. MT4 does not provide a message handling loop within the EA threads and so it is more problematic to show DLL windows.

The way around this is to create a new thread in your DLL which will provide the message processing capabilites a window(s) requires.

Whilst the coding of a DLL to interact with a single EA is slightly easier this example shows how to deal with multiple EAs Using the same DLL and window, and can be used for either single or multiple EA users.

I've tried to keep the code as simple as possible whilst providing a decent level of functionality, or at least to show how flexible this basic DLL is, all the while highlighting the pitfalls and showing how to avoid them.
Conversion to any C compiler shouldnt cause any major headaches provided the coder knows how to create a basic DLL and get it running within an Mt4 EA or indicator.
To sum up, the framework of this DLL can be easily be expanded to produce a complex (interactive) user interface to control or enhance any EA .


I've commented the Delphi source code quite extensively, but havent added much to the EA (MQ4) as its short 'n sweet and self explanitory.


If you dont know where the attached files need to go then you probably should'nt be playing with them, but just for the sake of it, the following files need to go in the stated locations :

DLL file -> MT4\experts\libraries
MQ4 file -> MT4\experts
All the other files are the Delphi project Source code and need to be placed in a single folder.


As a final caveat it was written using Delphi V4 running on Win XP With MT4 Build 509. I dont know if it will compile on later versions of Delphi or whether it will run correctly on later versions of windows but I cant see any reasons why it wouldnt.


I hope this helps anybody out there struggling to achieve what can be a pain in the a$$ to code.

*************************************************************************************
Appologies to all initial 7 downloaders. I have debugged the DLL code and found two errors in the initial release.

These errors were :

Bug : Incorrect freeing of objects during deint unless the DLL is unloaded from memory
Symptom : If you have this EA(s) open and recompile the MQ4 file then It will not initialise correctly

Bug : Failure to wait for DLL thread to create our main DLL window.
Symptom : Fails to initialise correctly in an unpredictable and often inconsistent manner.

Hi Rangebound,
Thanks a lot for this piece of code...
I thought I was quit a good Delphi developper (ok long time ago...) but I need to have a deeper look to your code, and you are definitly far away from my skill level... This is more than I was expected and percfectly commented!
Once again thanks a lot, I can now go further on my project...
Regards,
Olivier

PS : And so before posting this reply, I compilled the DLL, the mql4 expert... attach the EA to a chart and ... ran into troubles!
Let me investigate and I will come back later...

Win7 64bits
MT4 -32 bits - Build 579
Delphi XE2
DLLWindowsForMultipleEAs - 32 bits...

I'm not sure what to suggest on this other than I'm running Build 509, and I've noticed a couple of threads on FF about problems with builds 579 and 600 so that may be the cause.

I did have a few init errors early on in the coding, but they were resolved and I didnt get any later on and cant replicate them now.

I'll have a little play around and see if I can break it but without uild 579 Im not sure I'll get anywhere.

If I read your post correctly you compiled the DLL OK. If thats the case and you're running your compiled DLL rather than the one in the zip file then I suppose a problem could have crept through but I doubt this as your Pick clearly shows that the window is created successfully (if there a problem jumping to win 7 I'd have thought it would be to do with the call to GetWindowLong/SetWindowLong)

In the meantime if my above asumption is correct then I'd suggest using the DLL file in the Zip file (the one I compiled)

Anyway I'll see what I can do later on

Message to all initial 7 downloaders of this file

Please redownload the attachement in the 1st post of this thread.

I've recoded to avoid two stupid errors and all should be Good now.

I've also included the EX4 file in the zip incase users of build 579 & 600 are still having problems.

As I understand it (after a brief peek at the 579 and 600 problem threads) If you use the EX4 that was compiled on build 509 then
this should solve the problems for these newer builds. I hope this is correct.


Och can you please post back here if the updates work out OK for you.

Dear Rangebound,
I did not test it that much for the moment, I just reload the new release you posted on post#1, recompile the DLL and attached it to a chart on a MT4 579 Build and ... everything seems to be .... OK!
Thanks a million, as I would probably pass more than a couple of hours to fix it!
Thanks a lot for this starting point, now I can acheive my project : you'd just made the most difficult part!
Regards,
Olivier

EDIT : Since, I tried to add another chart, a new tab is correctly added and messages are correctly sent and received. Removing the ea used to crach MT4, it is not the case any more. Removing an EA correctly delete the tab and close the window if there are no more tabs! Just perfect.

No Problem Och.

Even though the hard work of the basic frame work is there for you now, you're still going to have your work cut out for you since you want multiple Eas attaching to the Single DLL.
You're either going to have to do as I have done and dynamically create your visual interface (which is a pain in the but)
or you'll have to code methods for storing EA specific data into DLL local vars & objects and restoring these data to the visual controls whenever the
user changes the tab control.


Anyway I'm just glad its up and running on your build and in 64 bit windows 7 too.

Have fun !!!

hi rangebound

thank you for this zip.As my developping skills are not that good, may i ask you to help on a very precise need : i would like to draw a button on a chart and execute an associated action when the mouse clicks on it. but this is far away from my developping skills. could you give a hand on that with an example ? thanx in advance.

Thanks rangebound for your excellent sourcecode as an example and the good documentation.

I am a delphideveloper for many years, but this peace of code is that was I searched a long time and my skills weren't enough to get this done.

My pupose is to make a window to change Parameter to my EA (tradingrobot) during runtime.
So I will modify your code for my requirements.

Thanks once more

Dear Rangebound,
I restarted that project 2 days ago and can't figure out why the loggerAddWatchArrayDouble exported procedure is not working. Instead of a long explanation, I am quite sure if you have some time and a look to the archive enclosed you will understand my issue. I can live without that function, but I would like to understand...
Regards,
Olivier

PS : I add a TVirtualStringTree component, so you need to install the package if you want to be able to compile the project...

PS2 : once again, thanks for your help.

hello rangebound,

i want to make ea like trade copier. i want to use a dll, like windows user32.dll bcoz i found many of them use it.they used two func of this dll

#import "user32.dll"
int PostMessageA(int hWnd,int Msg,int wParam,int lParam);
int RegisterWindowMessageA(string lpString);
#import

my question is,
1) what parameter i send to with this function like int PostMessageA(what,what,what,what) or RegisterWindowMessageA(string lpString);

2) i read somethings like 10milisecond execution , what i that, is this possible using this dll only.

3) i want some example how this dll works with the code, is that use only in the import section or it has any other uses.

plaese give some coding example or any tradecopier in mql4 version.