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Hello,
I wrote a native C++ dll which contains a class to hook windows messages.
As the callback function, I send a function pointer to my callback which is inside of my dll, but outside of the class.
I want a new instance of the function to be created for each instance of the class.
However, I can't declare my callback as non-static.
If I move my callback inside the class, and remove the static keyword I get a compile error saying:
"error C2440: 'type cast' : cannot convert from 'overloaded-function' to 'HOOKPROC'".
What can I do?
Any workarounds?
Thanks in advance,
Shy.
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A callback that the operating sytem calls must be static.
There is only one instance of a function, whether the function is static or not. The only difference between a static and non-static member function is the this pointer.
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With that said, how can I workaround this issue?
I need my callback to use instance variables, but of course it's not possible as they have to be static also.
If I use static variables it won't be any good to me...
Help...??
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You did not state clearly whether this is a system-wide hook. Is it, or is it a thread-specific hook?
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System-wide...
What's the difference when it comes to the static callback?
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I won't waste my time trying to help you further.
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Is it a callback that doesn't have a userdata parameter of some kind? Generally you can pass
an instance reference/pointer to methods that use a callback which will be passed to the callback.
In the callback it is cast to the proper type and used to access members. If it's your own
callback scheme then it should be easy to add a parameter.
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Mark Salsbery wrote: Generally you can pass an instance reference/pointer to methods that use a callback which will be passed to the callback.
In the callback it is cast to the proper type and used to access members.
I'm not sure I understand...
Could you please rephrase it...?
Mark Salsbery wrote: If it's your own callback scheme then it should be easy to add a parameter.
It's not my callback scheme...
I use SetWindowsHookEx(), thus I'm forced to use the following signature:
static LRESULT CALLBACK MsgCallback(UINT nCode, WPARAM wParam, LPARAM lParam)<br />
Again, I'm not really sure what you meant.
I'll point out again that I'm writing a native C++ dll.
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shyagam wrote: I'm not sure I understand...
Could you please rephrase it...?
I was referring to callbacks like the one used with EnumChildWindows() where there's a parameter
(app-defined) that you can pass to EnumChildWindows() which will be passed to the callback
fuction. You can pass an object pointer as this parameter and retrieve it in the static callback
and use it to access members of the object class.
With SetWindowsHookEx() you don't have this available. You're going to need an object reference
or pointer in the callback to get at any of the object class' non-static members. You could
store this pointer/reference somewhere - global variable, static member variable. Without it
you only have access to static members, as you know.
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Thanks for the quick reply... 
Mark Salsbery wrote: You could store this pointer/reference somewhere - global variable, static member variable.
I was thinking of holding a static list to all class instances.
Each constructor call would add the this pointer to the list.
The class would have an inner callback function.
The callback sent to SetWindowsHookEx() would then run a loop and call the inner callback inside each of the list's elements.
Do you see any potential flows in this?
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Sounds like a plan Don't forget to thread-protect access to that list 
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Mark Salsbery wrote: Don't forget to thread-protect access to that list
Absolutly right... I'll keep that in mind! 
Thanks again!
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Using VS2005, if I was to run NOTEPAD.EXE from within an application - how would this be achieved ?
Pete
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Can anyone tell me how I make an application run like a service(to start with windows,do not have a bar in the tool box like whe you enter My Computer) please
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Is this a Turbo C++ or a native C++ question? If yes, you are in the wrong forum.
"We make a living by what we get, we make a life by what we give." --Winston Churchill
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How do you make an app to like a windows app(the blue title bar) I've tried to find over the internet but no luck:
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Is your question related to Turbo C++ (You asked a similar question in the C++ forum) or to C++/CLI which is a managed version of C++ for .NET?
"We make a living by what we get, we make a life by what we give." --Winston Churchill
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using namespace System::Text::RegularExpression;
if (!Regex::IsMatch("[a-zA-Z0-9]{4,13]"))
{
MessageBox::Show("Username must be at least 4 char long, it can contain letters and numbers. Maximum lneght is 13 char");
}
Error 1 error C2352: 'System::Text::RegularExpressions::Regex::IsMatch' : illegal call of non-static member function c:\projects\cddvdorganizer\cddvdorganizer\frmAddUser.h 281
How can i avoid this problem.
Thanks in advance
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The error message gave you the answer! Regex::IsMatch is not static. You have to create an instance of Regex first.
"We make a living by what we get, we make a life by what we give." --Winston Churchill
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George L. Jackson wrote: The error message gave you the answer! Regex::IsMatch is not static. You have to create an instance of Regex first.
No i don't need to create static. I yust found an error. IsMatch uses 2 parameters. Code belove works fine
if (Regex::IsMatch(txtUserName->Text, "[a-zA-Z0-9]{4,13}") == false)
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My bad! I just noticed that IsMatch has four overloads. Two of them are static.
George
"We make a living by what we get, we make a life by what we give." --Winston Churchill
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Dear Friends..Can any one tell me about operator ":"
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You cam use ":" with "?". In the following example, the "?" can be interpreted as "then" and the ":" as else.
int result = i > 10 ? 9 : 11;
This is equivalent to:
<br />
if (i > 10)<br />
result = 9;<br />
else<br />
result = 11;<br />
The ":" is also used with "public", "private" and "protected" to define security access within a class and inheritance.
<br />
clas Derived : public Base<br />
{<br />
public:<br />
protected:<br />
private:<br />
};<br />
You also use it to create a constructor initialize list in classes:
<br />
class Foo<br />
{<br />
public:<br />
Foo() : value(1) {}<br />
protected:<br />
private:<br />
int value;<br />
};<br />
George
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the operator : doesn't exist
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