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What is the point of function objects? Are these a leftover from the primitive days of STL? In case you haven't seen these they look like this:
class PrintInt {
public:
void operator() (int elem) const {
cout << elem << ' ';
}
};
My neighbours think I am crazy - but they don't know that I have a trampoline. All they see my head bobbing up and down over the fence every five seconds
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Functors allow you to specialize standard algorithms. Imagine an algorithm that said "Perform X on the collection Y". X in this case would be the functor. Thus you can change the specifics of the algorithm without having to change the algorithm itself.
It is very powerful and can also lead to some HORRIBLE abuses. (i.e. algorithms converted to functor capable even though the resulting code is more complicated and harder to manage than the original code. Foreach "can" often fall into this category.)
Tim Smith
I'm going to patent thought. I have yet to see any prior art.
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They're useful for providing callbacks out of some generic algorithm. You can provide any object that offers a suitable operator().
They're often used for things like the predicate in find_if.
You'd use one in preference to a regular function if you needed to preserve some state.
If you need to conjure up a suitable function object from something that doesn't quite fit, you can use mem_fun, mem_fun_ref, ptr_fun, bind1st, bind2nd, and the other members of the <functional> header.
The Boost library has a similar concept (http://www.boost.org/doc/html/function.html[^]).
Stability. What an interesting concept. -- Chris Maunder
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What is this www.boost.com? Is it like CodeProject for STL?
My neighbours think I am crazy - but they don't know that I have a trampoline. All they see my head bobbing up and down over the fence every five seconds
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From the home page:
"The Boost web site provides free peer-reviewed portable C++ source libraries. The emphasis is on libraries which work well with the C++ Standard Library. The libraries are intended to be widely useful, and are in regular use by thousands of programmers across a broad spectrum of applications.
"A further goal is to establish "existing practice" and provide reference implementations so that Boost libraries are suitable for eventual standardization. Ten Boost libraries will be included in the C++ Standards Committee's upcoming C++ Standard Library Technical Report as a step toward becoming part of a future C++ Standard."
A list of components can be found at http://www.boost.org/libs/libraries.htm[^].
Stability. What an interesting concept. -- Chris Maunder
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How can I know, in a multi-threaded application, the state of certain thread? Let's say, I need to know if it's paused or running.
Greetings,
D.
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Try setting a bool value bool isrunning;
And have it set itself to true while the thread is running then after the thread stops right before the AfxEndThread(0); set it back to false.
or you could have something like this.
1) make an edit box
2) give the edit box a member variable of type CEdit call it m_example
3) under OnInit() or whatever function is called to initialize your dialog or window that you are using put m_example.SetWindowText("NOT RUNNING");
4) then inside the run() of your thread make the first line before it does its while statement. m_example.SetWindowText("IS RUNNING");
5) after the while statement and before AfxEndThread(0); put m_example.SetWindowText("NOT RUNNING");
I hope this makes sense. There might be a better way since i'm just starting Visual myself, but anyway this should work.
Win32newb
"Making windows programs worse than they already are"
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win32newb wrote:
4) then inside the run() of your thread make the first line before it does its while statement. m_example.SetWindowText("IS RUNNING");
You should not make calls to editbox that is owned by another thread from the new thread... it will crash.
MSN Messenger.
prakashnadar@msn.com
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Well, ok, what if I have numerous threads? Let's say at least four? How to know if thread is paused or running? Any interesting approaches?
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How about OpenThread and GetThreadContext.
Not sure what is in a CONTEXT, but I would suspect if it was the same from one call to the next, that the thread was suspended.
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Howdy,
I am writing a client side MFC application. I would like to be able to display a scrolling window that renders simple html. The main tags I need are <font>, <center>, <strong> and maybe <img>.
I don't want to use the MS Internet explorer control. That's like using a locomotive to push a shopping cart. My client doesn't want the dependancies and security issues that come with IE. I don't blame him a bit.
I know I have seen light weight html rendering controls for simple html text rendering, but I can't remember where I saw them.
Anyone have any suggestions?
TIA
Jim H
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Since IE is already available on the machine, why not use it? While other renderers probably exist, can you guarantee that they have been thoroughly tested and are fully HTML compliant? Have you considerd CHtmlView? It's based on the IE server, but it plugs into an application almost seamlessly.
"The pointy end goes in the other man." - Antonio Banderas (Zorro, 1998)
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I've deployed commerical apps that use CHtmlView. It can work, but it's a hellish nightmare to test all the possible permutations and combinations of operating systems and versions of IE. My client also has legitimate security concerns about using IE.
If you need the full power of IE then using the MS browser object is fine.
I don't need anything like the power of IE. I just need to be able to nicely render some text. IE is massive overkill for this task.
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HTMEngine at http://www.terrainformatica.com/htmengine/
QHTM at http://www.gipsysoft.com/qhtm/
--
Joel Lucsy
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Well it's not exactly an HTML rendering engine, but the following control has support for a bunch of tags. I haven't looked at the source that I can remember, but you may be able to rip out it's core and use it for your own purposes.
http://www.codeproject.com/miscctrl/pptooltip.asp[^]
Chris Richardson
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Hey,
here's a good newbie question for everyone:
I'm currently using a 2d graph DLL that i got from codeproject:
CXGraph
And am running it on a split pane with a control panel the right. when the user clicks on the graph, i want to pull the value for that point on the graph out of the graph dll and access it in my project, but the click message seems to get caught in the graph function.
is there any way i can catch the mouseclick action in the main app?
Many Thanks,
Mike
"Facts are meaningless. You could use facts to prove anything that's even remotely true." --Homer J.
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You could intercept it in your derived class then post it back to the MainWnd
AfxGetMainWnd()->PostMessage(...
My neighbours think I am crazy - but they don't know that I have a trampoline. All they see my head bobbing up and down over the fence every five seconds
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thanks!
that's what i was looking for
"Facts are meaningless. You could use facts to prove anything that's even remotely true." --Homer J.
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Hello, there,
I am currently working on a project. There is a combo box. I'd like to know how I can disable the dropdown arrow of it or hide the dropdown arrow. In my project there is two setting, one is keeping the input history, one is not keeping the input history.
I tried m_Combo.ShowDropDown(false)when not keeping the history, but there is a black line under it and it doesn't look good. Is there a way to solve this problem?
Thanks a lot in advance.
Bin
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One way is to subclass the control, and handle WM_LBUTTONDOWN yourself, to effectively disable it that way, or alternatively, at run-time create an edit control in it's place which is ES_READONLY.
Steve S
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If your wanting to disable it do this
have a combo box and give it a control name like m_example
then on your button or whatever your using
lets say your using a button and the button is called History
you put under OnHistory()
m_example.EnableWindow(FALSE); // disabled combobox or whatever linked to
m_example.EnableWindow(TRUE); // enables combobox or whatever linked to
now if you wanna hide it all together
i would do this under the OnHistory()
m_example.ShowWindow(SW_HIDE); // hides the combobox or whatever linked to
if you want the window back then
m_example.ShowWindow(SW_SHOW);// shows the combobox or whatever linked to
GOOD LUCK,
HOPE THIS HELPS.
Win32newb
"Making windows programs worse than they already are"
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thanks a lot. But I just want to disable the drop down button and make it work as an edit box. I don't want to disable the whole thing.
Thanks.
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what you can do is:
Just iterate the windows of the combo box. Combo box contains the edit box and the button.
For example
char szClassName[256];
CWnd* pWnd=(CWnd *)m_combo.GetWindow(GW_CHILD);
::GetClassName(pWnd->GetSafeHwnd(), szClassName, 256);
while( strcmp( szClassName,_T("Button")) != 0 )
{
pWnd=(CWnd *)m_combo.GetWindow(GW_HWNDNEXT);
}
//Got the button
if( pWnd )
pWnd->ShowWindow( SW_HIDE );
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Thanks alot, very helpful hint!! 
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I have seen issues with something that works fine in all Windows OS's except some machines running 2000 or XP. I'm using a WM_COPYDATA to send text between windows. When it fails, messages that should appear do not. It is extremely hard to narrow it down further than that.
Is anyone aware of any issues using this message on the newer OS's?
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