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  • C++/Qt - Memory allocation question

    - by HardCoder1986
    Hello! I recently started investigating Qt for myself and have the following question: Suppose I have some QTreeWidget* widget. At some moment I want to add some items to it and this is done via the following call: QList<QTreeWidgetItem*> items; // Prepare the items QTreeWidgetItem* item1 = new QTreeWidgetItem(...); QTreeWidgetItem* item2 = new QTreeWidgetItem(...); items.append(item1); items.append(item2); widget->addTopLevelItems(items); So far it looks ok, but I don't actually understand who should control the objects' lifetime. I should explain this with an example: Let's say, another function calls widget->clear();. I don't know what happens beneath this call but I do think that memory allocated for item1 and item2 doesn't get disposed here, because their ownage wasn't actually transfered. And, bang, we have a memory leak. The question is the following - does Qt have something to offer for this kind of situation? I could use boost::shared_ptr or any other smart pointer and write something like shared_ptr<QTreeWidgetItem> ptr(new QTreeWidgetItem(...)); items.append(ptr.get()); but I don't know if the Qt itself would try to make explicit delete calls on my pointers (which would be disastrous since I state them as shared_ptr-managed). How would you solve this problem? Maybe everything is evident and I miss something really simple?

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  • Custom events and event pooling in jQuery - What's the point?

    - by Nick Lowman
    I've been reading about custom events in jQuery and why they should be used but I'm still clearly missing the point. There is a very good article I read here that has the following code example; function UpdateOutput() { var name = $('#txtName').val(); var address = $('#txtAddress').val(); var city = $('#txtCity').val(); $('#output').html(name + ' ' + address + ' ' + city); } $(document).bind('NAME_CHANGE ADDRESS_CHANGE CITY_CHANGE', function() { UpdateOutput(); }); $('#txtAddress').keyup(function() { $(document).trigger('ADDRESS_CHANGE'); }); $('#txtCity').keyup(function() { $(document).trigger('CITY_CHANGE'); }); Can someone tell me why I just don't call the UpdateOutput() function directly? It would still work exactly the same way, i.e. $('#txtAddress').keyup(function() { UpdateOutput() }); $('#txtCity').keyup(function() { UpdateOutput() }); Many thanks

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  • How to find out on which internet addresses a java program can listen.

    - by tzador
    My program needs to listen incoming socket connections (lets agree on port 8765), but it doesn't know which addresses it can bind on a particular machine. Of, course, it could simply to listen to all of them, but it need to send to the client program over a different(slower) channel the addresses which it should try in order to rich me on port 8765. So the flow is like this: My program lisens on all available interfaces on port 8765 Finds out a list of inet4 adresses by which it can be possibly reached (this step is the actual question) Posts that address on a whiteboard (blogpost or something) Interested clients try out all of them, to see using which one they can reach my program. This is all is to be done in java ofcourse :)

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  • WPF textblock binding question.

    - by the empirical programmer
    I'm trying to get my head around the whole MVVM thing and binding. I have a ViewModel class which has a property that is another class. I want to bind to a (string) property of that class to the text of a textblock. I set the ViewModel as my data context for my window\page. And then do this: <TextBlock Text="{Binding ElementName=myAddressClass, Path=StreetName}" /> But this does not work. The text is empty. I can expose the StreetName directly as below and this works: <TextBlock Text="{Binding Path=StreetName}" /> So am I doing something wrong in the first example. It seems simple enough ... am I just confuse about what an elementname is or should be set to? thanks

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  • How to access referenced table from ASPX in-line code (datagridview control)

    - by Grant
    Hi, i am trying to bind data to a datagridview control on an ASPX webpage and am using something like this.. <asp:TemplateField HeaderText="MyField"> <ItemTemplate> <%# DataBinder.Eval(Container.DataItem, "MyField") %> </ItemTemplate> </asp:TemplateField> the problem i am having is that the data for the 'MyField' field is actually an integer that is a reference to a string value in another sql table. Does anyone know how i can reformat my code line above to show the string value instead of the int value?

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  • Member function overloading/template specialization issue

    - by Ferruccio
    I've been trying to call the overloaded table::scan_index(std::string, ...) member function without success. For the sake of clarity, I have stripped out all non-relevant code. I have a class called table which has an overloaded/templated member function named scan_index() in order to handle strings as a special case. class table : boost::noncopyable { public: template <typename T> void scan_index(T val, std::function<bool (uint recno, T val)> callback) { // code } void scan_index(std::string val, std::function<bool (uint recno, std::string val)> callback) { // code } }; Then there is a hitlist class which has a number of templated member functions which call table::scan_index(T, ...) class hitlist { public: template <typename T> void eq(uint fieldno, T value) { table* index_table = db.get_index_table(fieldno); // code index_table->scan_index<T>(value, [&](uint recno, T n)->bool { // code }); } }; And, finally, the code which kicks it all off: hitlist hl; // code hl.eq<std::string>(*fieldno, p1.to_string()); The problem is that instead of calling table::scan_index(std::string, ...), it calls the templated version. I have tried using both overloading (as shown above) and a specialized function template (below), but nothing seems to work. After staring at this code for a few hours, I feel like I'm missing something obvious. Any ideas? template <> void scan_index<std::string>(std::string val, std::function<bool (uint recno, std::string val)> callback) { // code }

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  • WPF UserControl event called only once?

    - by 742
    Hi Everyone, I need to bind two-way a property of a user control to a property of a containing user control. I also need to set a default value to the property from code in the child (cannot be done easily from XAML tags). If I call my code from the child constructor, the value is set in the parent but the change callback routine is not triggered (my understanding is that the parent doesn't yet exist at the time the child is created). My current workaround is to catch the Loaded event of the child and to call the code from the handler. Howver as Loaded is called more than once, I need to set a flag to set the property only the first time. I don't like this way, but I don't know if there is a single shot event that could be used, or if this can be done otherwise. Any feedback based on your experience?

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  • wxpython : button covers all in the frame

    - by Prakash
    Below is my code: #!/usr/bin/python # -*- coding: utf-8 -*- import wx class Example(wx.Frame): def __init__(self): #super(Example, self).__init__(parent, title=title, size=(300, 200)) wx.Frame.__init__(self, None, wx.ID_ANY, 'wxButton', pos=(300, 150), size=(320, 250)) self.button1 = wx.Button(self, id=-1, label='Button1', pos=(8, 8), size=(10, 20)) self.button1.Bind(wx.EVT_BUTTON, self.button1Click) self.Centre() self.Show() def button1Click(self,event): #self.button1.Hide() self.SetTitle("Button1 clicked") if __name__ == '__main__': app = wx.App() Example() app.MainLoop() Actually I am expecting the button1 on the frame to have a look like a button - a bit raised and be placed in center of frame - but it is just expanding to the full frame. Also text Button1 looks like a text which does not has a button look like feeling? What wrong am I doing?

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  • jquery - sliding image group left and right (hiding the ones that are past a certain point)

    - by matthewsteiner
    So I'm not really sure how to go about doing this at all. I've got an anchor on the left with id="left" and one on the right with id="right". On the hover event, the image thumbnails should start sliding left or right. If there's not enough thumbnails, there should be no sliding. It can only fit 4 images in between the left and right anchors. How can I hide all anchors that are not in between the left and right anchors? I want the images to actually slowly move left or right, not just be sudden. Any ideas? I know how to bind the events and such just fine. I just don't really now how to get started with the image placement.

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  • Convert Yes/No/Null from SQL to True/False in a DataTable

    - by Scott Chamberlain
    I have a Sql Database (which I have no control over the schema) that has a Column that will have the varchar value of "Yes", "No", or it will be null. For the purpose of what I am doing null will be handled as No. I am programming in c# net 3.5 using a data table and table adapter to pull the data down. I would like to directly bind the column using a binding source to a check box I have in my program however I do not know how or where to put the logic to convert the string Yes/No/null to boolean True/False; Reading a null from the SQL server and writing back a No on a update is acceptable behavior. Any help is greatly appreciated. EDIT -- This is being developed for windows.

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  • asp.net refresh part of page whit jquery when application state change

    - by Jeson Park
    i use Application property to count number of online users Application["OnlineUsers"] = (int)Application["OnlineUsers"] + 1; and then bind Application property value to HTML tag <div id="OnlineUser" > <span>Number of Online Users is <%=Application["OnlineUsers"].ToString() %></span> </div> when for example "user1" visit page,DIV tag show "Number of Online Users is 1" and "user2" visit page,DIV tag show "Number of Online Users is 2" but user1 still "Number of Online Users is 1" how do i refresh user1 page when user2 change application peroperty?

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  • Chat Server with sockets in C

    - by Andrew
    I'm trying to write a chat server in C that allows communication between two clients using POSIX sockets. I'm not sure I have a good grasp on this concept or how I should set up the communication protocol between the clients and the server. I know I need one socket to bind() the server port to so I can accept incoming connections from clients, but in order to have two clients connected at the same time do I need to create a socket for each of these clients when I accept() or should I accept() a client and then fork() so I can have another client accept? I'm not worried about concurrent chatting yet, it's more of a ping-pong approach where the clients need to wait for a recv() after they send() before they can type a new message.

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  • Python Tkinter after loop not working fast enough

    - by user2658538
    I am making a simple metronome where it plays a tick sound every few milliseconds depending on the bpm and plays the sound using the winsound module. I use tkinter because there will be a gui component later but for now the metronome code is working, it plays the sound at a constant rate, but even though I set the after loop to play the sound every few milliseconds, it waits longer and the beat is slower than it should be. Is it a problem with the code or a problem with the way I calculate the time? Thanks. Here is my code. from Tkinter import * import winsound,time,threading root=Tk() c=Canvas(root) c.pack() class metronome(): def __init__(self,root,canvas,tempo=100): self.root=root self.root.bind("<1>",self.stop) self.c=canvas self.thread=threading.Thread(target=self.play) self.thread.daemon=True self.pause=False self.tempo=tempo/60.0 self.tempo=1.0/self.tempo self.tempo*=1000 def play(self): winsound.PlaySound("tick.wav",winsound.SND_FILENAME) self.sound=self.c.after(int(self.tempo),self.play) def stop(self,e): self.c.after_cancel(self.sound) beat=metronome(root,c,120) beat.thread.start() root.mainloop()

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  • Creating serializeable unique compile-time identifiers for arbitrary UDT's.

    - by Endiannes
    I would like a generic way to create unique compile-time identifiers for any C++ user defined types. for example: unique_id<my_type>::value == 0 // true unique_id<other_type>::value == 1 // true I've managed to implement something like this using preprocessor meta programming, the problem is, serialization is not consistent. For instance if the class template unique_id is instantiated with other_type first, then any serialization in previous revisions of my program will be invalidated. I've searched for solutions to this problem, and found several ways to implement this with non-consistent serialization if the unique values are compile-time constants. If RTTI or similar methods, like boost::sp_typeinfo are used, then the unique values are obviously not compile-time constants and extra overhead is present. An ad-hoc solution to this problem would be, instantiating all of the unique_id's in a separate header in the correct order, but this causes additional maintenance and boilerplate code, which is not different than using an enum unique_id{my_type, other_type};. A good solution to this problem would be using user-defined literals, unfortunately, as far as I know, no compiler supports them at this moment. The syntax would be 'my_type'_id; 'other_type'_id; with udl's. I'm hoping somebody knows a trick that allows implementing serialize-able unique identifiers in C++ with the current standard (C++03/C++0x), I would be happy if it works with the latest stable MSVC and GNU-G++ compilers, although I expect if there is a solution, it's not portable.

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  • passing paramter as to webservcie function in wcf

    - by prince23
    hi, this my datagrid event here i am calling the webservice. private void dgProject_RowDetailsVisibilityChanged(object sender, DataGridRowDetailsEventArgs e) { WSDataServiceClient wsService = new WSDataServiceClient(); wsService.GetProjectCompleted += new EventHandler<GetProjectCompletedEventArgs>(wsService_GetProjectCompleted); wsService.GetProjectAsync(strUniqueName); // here can i send datagrid as an parameter to the function? Datagrid gd= new Datagrid(); } void wsService_GetProjectCompleted(object sender, GetProjectCompletedEventArgs e) { // } is there any way that i can send datagrid as a paramter to this function is it possiable to do? beacuse i will be using the same websevice function her but need to bind result with different datagrid based on the condition if i can send a datagrid as paramter to this function i can reduce the code so any help on this issue would be great thank you.

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  • Best strategy for HTML parcial rendering based on multiple dropdown values

    - by pv2008
    I have a View that renders something like this: "Item 1" and "Item 2" are <tr> elements from a table. After the user change "Value 1" or "Value 2" I would like to call a Controller and put the result (some HTML snippet) in the div marked as "Result of...". I have some vague notions of JQuery. I know how to bind to the onchage event of the Select element, and call the $.ajax() function, for example. But I wonder if this can be achieved in a more efficient way in ASP.NET MVC2.

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  • Prevent auto scrolling when clicking tab anchor

    - by JohnCrossy
    On my page I have some tabs that I've added some javascript so when they're clicked the page loads the tab's anchor URL instead of simply changing the view with AJAX, but I now want to stop the browser from auto scrolling to the anchor location. Having done some research, I'm pretty sure I just need to add a couple of lines so that when clicked it returns false or prevents default but, being a noob, I've no idea where to put them!?! I know it's cheeky, but if any answers could include the full script (ie. the below) with the solution, that way I'll understand better and hopefully learn some valuable lessons also :) Here's the code I'm using: jQuery( function() { jQuery('.ui-tabs').bind( 'tabsselect', function( e, ui ) { window.location.hash = ui.tab.hash }); });

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  • C++ template overloading - wrong function called

    - by DeadMG
    template<typename T> T* Push(T* ptr); template<typename T> T* Push(T& ref); template<typename T, typename T1> T* Push(T1&& ref); I have int i = 0; Push<int>(i); But the compiler calls it ambiguous. How is that ambiguous? The second function is clearly the preferred match since it's more specialized. Especially since the T1&& won't bind to an lvalue unless I explicitly forward/move it. Sorry - i is an int. Otherwise, the question would make no sense, and I thought people would infer it since it's normally the loop iterator.

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  • Get id from a one div to another div

    - by Jean
    Hello Here are the two divs <div id="1"> <span id="a1">first</span> <span id="a2b">first</span> <span id="a3">first</span> </div> Click <div id=2></div> And the jQuery code to do $('#2').bind('click',function(){ var xx = $('#a'+i).attr('id'); $('#2').append(xx); i=i+1; }); It does not get all the 3 id's from #1 Thanks Jean

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  • Behaviour to simulate an enum implementing an interface

    - by fearofawhackplanet
    Say I have an enum something like: enum OrderStatus { AwaitingAuthorization, InProduction, AwaitingDespatch } I've also created an extension method on my enum to tidy up the displayed values in the UI, so I have something like: public static string ToDisplayString(this OrderStatus status) { switch (status) { case Status.AwaitingAuthorization: return "Awaiting Authorization"; case Status.InProduction: return "Item in Production"; ... etc } } Inspired by the excellent post here, I want to bind my enums to a SelectList with an extension method: public static SelectList ToSelectList<TEnum>(this TEnum enumObj) however, to use the DisplayString values in the UI drop down I'd need to add a constraint along the lines of : where TEnum has extension ToDisplayString Obviously none of this is going to work at all with the current approach, unless there's some clever trick I don't know about. Does anyone have any ideas about how I might be able to implement something like this?

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  • Can't append to second container

    - by George Katsanos
    I have the following script: (function($) { $.fn.easyPaginate = function(options){ var defaults = { step: 4, delay: 100, numeric: true, nextprev: true, controls: 'pagination', current: 'current' }; var options = $.extend(defaults, options); var step = options.step; var lower, upper; var children = $(this).children(); var count = children.length; var obj, next, prev; var page = 1; var timeout; var clicked = false; function show(){ clearTimeout(timeout); lower = ((page-1) * step); upper = lower+step; $(children).each(function(i){ var child = $(this); child.hide(); if(i>=lower && i<upper){ setTimeout(function(){ child.fadeIn('fast') }, ( i-( Math.floor(i/step) * step) )*options.delay ); } if(options.nextprev){ if(upper >= count) { next.addClass('stop'); } else { next.removeClass('stop'); }; if(lower >= 1) { prev.removeClass('stop'); } else { prev.addClass('stop'); }; }; }); $('li','#'+ options.controls).removeClass(options.current); $('li[data-index="'+page+'"]','#'+ options.controls).addClass(options.current); if(options.auto){ if(options.clickstop && clicked){}else{ timeout = setTimeout(auto,options.pause); }; }; }; function auto(){ if(upper <= count){ page++; show(); } else { page--; show(); } }; this.each(function(){ obj = this; if(count>step){ var pages = Math.floor(count/step); if((count/step) > pages) pages++; var ol = $('<ol id="'+ options.controls +'" class="pagin"></ol>').insertAfter(obj); if(options.nextprev){ prev = $('<li class="prev">prev</li>') .appendTo(ol) .bind('click', function() { //check to see if there are any more pages in the negative direction if (page > 1) { clicked = true; page--; show(); } }); } if(options.numeric){ for(var i=1;i<=pages;i++){ $('<li data-index="'+ i +'">'+ i +'</li>') .appendTo(ol) .click(function(){ clicked = true; page = $(this).attr('data-index'); show(); }); }; }; if(options.nextprev){ next = $('<li class="next">next</li>') .appendTo(ol) .bind('click', function() { //check to see if there are any pages in the positive direction if (page < (count / 4)) { clicked = true; page++; show(); } }); } show(); }; }); }; })(jQuery); jQuery(function($){ $('ul.news').easyPaginate({step:4}); }); which is a carousel-like plugin that produces this html structure for the navigation: <ol id="pagination" class="pagin"><li class="prev">prev</li><li data-index="1" class="">1</li><li data-index="2" class="">2</li><li data-index="3" class="current">3</li><li class="next stop">next</li></ol> And all I want is to enclose this list in a div. Seems simple, but appendTo doesn't want to cooperate with me, or I'm doing something wrong (I'd appreciate if you would help me understand what that is..) So I'm modifying as such: var ol = $('<ol id="'+ options.controls +'" class="pagin"></ol>'); var tiv = $('<div id="lala"></div>'); ol.appendTo('#lala'); tiv.insertAfter(obj); I know how to chain, but I'm in "debugging" mode trying to understand why I don't get the result I imagine I would get: <div id="lala> <ol id="pagination><li>...... </li></ol> </div> I tried putting some console.log's to see the status of my variables but couldn't find something useful.. I guess there's something with DOM insertion I don't get.

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  • How can I write a function template for all types with a particular type trait?

    - by TC
    Consider the following example: struct Scanner { template <typename T> T get(); }; template <> string Scanner::get() { return string("string"); } template <> int Scanner::get() { return 10; } int main() { Scanner scanner; string s = scanner.get<string>(); int i = scanner.get<int>(); } The Scanner class is used to extract tokens from some source. The above code works fine, but fails when I try to get other integral types like a char or an unsigned int. The code to read these types is exactly the same as the code to read an int. I could just duplicate the code for all other integral types I'd like to read, but I'd rather define one function template for all integral types. I've tried the following: struct Scanner { template <typename T> typename enable_if<boost::is_integral<T>, T>::type get(); }; Which works like a charm, but I am unsure how to get Scanner::get<string>() to function again. So, how can I write code so that I can do scanner.get<string>() and scanner.get<any integral type>() and have a single definition to read all integral types? Update: bonus question: What if I want to accept more than one range of classes based on some traits? For example: how should I approach this problem if I want to have three get functions that accept (i) integral types (ii) floating point types (iii) strings, respectively.

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  • How to determine IP used by client connecting to INADDR_ANY listener socket in C

    - by codebox_rob
    I have a network server application written in C, the listener is bound using INADDR_ANY so it can accept connections via any of the IP addresses of the host on which it is installed. I need to determine which of the server's IP addresses the client used when establishing its connection - actually I just need to know whether they connected via the loopback address 127.0.0.1 or not. Partial code sample as follows (I can post the whole thing if it helps): static struct sockaddr_in serverAddress; serverAddress.sin_family = AF_INET; serverAddress.sin_addr.s_addr = INADDR_ANY; serverAddress.sin_port = htons(port); bind(listener, (struct sockaddr *) &serverAddress, sizeof(serverAddress)); listen(listener, CONNECTION_BACKLOG); SOCKET socketfd; static struct sockaddr_in clientAddress; ... socketfd = accept(listener, (struct sockaddr *) &clientAddress, &length);

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  • Binding Click event in KnockoutJS

    - by user1918553
    I have a which has a css binding according to the value of 'rowState' as follows which is working fine. Now, I need to bind the 'click' event to fire only if the rowState is not 2. I tried the following, but with no success. I do not want to use the if statement as the div has got lots of content which I would need to repeat. The only difference is to make the div not clickable if rowState is 2. Could you please help me to sort this out?

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  • What wrapper class in C++ should I use for automated resource management?

    - by Vilx-
    I'm a C++ amateur. I'm writing some Win32 API code and there are handles and weirdly compositely allocated objects aplenty. So I was wondering - is there some wrapper class that would make resource management easier? For example, when I want to load some data I open a file with CreateFile() and get a HANDLE. When I'm done with it, I should call CloseHandle() on it. But for any reasonably complex loading function there will be dozens of possible exit points, not to mention exceptions. So it would be great if I could wrap the handle in some kind of wrapper class which would automatically call CloseHandle() once execution left the scope. Even better - it could do some reference counting so I can pass it around in and out of other functions, and it would release the resource only when the last reference left scope. The concept is simple - but is there something like that in the standard library? I'm using Visual Studio 2008, by the way, and I don't want to attach a 3rd party framework like Boost or something.

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