Yes it makes perfect sense. I would generally prefer using the boost/stdlib functions where possible rather than their Qt alternatives. 
   
It makes the code easier to port to the next framework.   
It makes is easier for new non-Qt programmers to get upto speed.   
Boost has some great functionality and is getting more all the time.   

note: strings to/from widgets are probably the main exception - inside the GUI I would use Qt strings to save confusing casts everywhere.





[This paper][1] compares [signal slots][2] mechanism in QT and [Boost::Signal][3] very decently. It is a must read for those who are a bit curious of this mix.


  [1]: http://www.elpauer.org/stuff/a_deeper_look_at_signals_and_slots.pdf
  [2]: http://doc.qt.io/qt-4.8/signalsandslots.html
  [3]: http://www.boost.org/doc/html/signals.html

Especially since you are going cross-platform, you should have a nicely layered architecture, with the business logic and data access as removed as possible from the GUI.  In this case, it would make sense to use Boost when writing the backend of your application, and only jump to Qt for the frontend, with the mandatory pile of casts done in the glue. 

If your &quot;engine&quot; is separate from your GUI choice, you will be able to swap out Qt for something else in the future (native libraries perhaps) with minimal effort.

We (Last.fm) use them both together, though we only just started to do so, and so haven&#39;t a good deal of experience yet. So far everything is fine though :)

There are potential problems with using Boost.Signals alongside QT. These are documented in the [Boost.Signals FAQ](http://www.boost.org/doc/libs/release/doc/html/signals/s04.html).

Consider that [Boost Signals2][1] are available, and they are thread safe.


  [1]: http://www.boost.org/doc/libs/1_45_0/doc/html/signals2.html

We work extensively in the .Net Compact Framework and Windows Mobile. I&#39;ve seen plenty of questions come up regarding specifics to development of ASP.Net apps or other .Net based desktop apps but nothing CF specific.

Anyone else a mobile developer out there that can share some things to start doing, stop doing, and avoid doing when developing in the Compact Framework?

What are the most valuable .Net Compact Framework Tips, Tricks, and Gotcha-Avoiders?

I&#39;m trying to do this:

    cmd.exe /C &quot;C:\Program Files\Somewhere\SomeProgram.exe&quot; &gt; &quot;C:\temp\Folder Containing Spaces\SomeProgram.out&quot;

However, I have problems which are down to the way cmd.exe works. If you read the help for it, it handles &quot; characters in a special way. See the help at the end of question. So, this doesn&#39;t execute correctly... I&#39;m guessing cmd.exe strips some quotes which makes the statement ill-formed.

I can do this successfully:

    // quotes not required around folder with no spaces
    cmd.exe /C &quot;C:\Program Files\Somewhere\SomeProgram.exe&quot; &gt; C:\temp\FolderWithNoSpaces\SomeProgram.out

But, I really need the first one to work. Is there away around the strange quote processing that cmd.exe uses? I want it to preserve all of the quotes, but there doesn&#39;t appear to be an option to make it do that.

----------
**Help taken from output of: cmd /?**

If /C or /K is specified, then the remainder of the command line after
the switch is processed as a command line, where the following logic is
used to process quote (&quot;) characters:

    1.  If all of the following conditions are met, then quote characters
        on the command line are preserved:

        - no /S switch
        - exactly two quote characters
        - no special characters between the two quote characters,
          where special is one of: &amp;&lt;&gt;()@^|
        - there are one or more whitespace characters between the
          the two quote characters
        - the string between the two quote characters is the name
          of an executable file.

    2.  Otherwise, old behavior is to see if the first character is
        a quote character and if so, strip the leading character and
        remove the last quote character on the command line, preserving
        any text after the last quote character.



How do I deal with quote characters when using cmd.exe

I&#39;m looking at starting a project in C++ using the Qt 4 framework (a cross-platform GUI is required).  I&#39;ve heard great things about the Boost libraries from friends and online.  I&#39;ve started reading up on both and wanted to ask a cursory question before I got too deep: Are these two development &quot;systems&quot; mutually exclusive? 

My initial searching and reading shows some overlap in the signal handling, custom build systems, and other low-level primitives.

Does it make sense to use them both in the same project?



Mixing Qt and Boost

I'm looking at starting a project in C++ using the Qt 4 framework (a cross-platform GUI is required). I've heard great things about the Boost libraries from friends and online. I've started reading up on both and wanted to ask a cursory question before I got too deep: Are these two development "systems" mutually exclusive?
My initial searching and reading shows some overlap in the signal handling, custom build systems, and other low-level primitives.
Does it make sense to use them both in the same project?

I have a situation where I need to process large (many GB&#39;s) amounts of data as such:

1. build a large string by appending many smaller (C char*) strings
2. trim the string
3. convert the string into a C++ const std::string for processing (read only)
4. repeat

The data in each iteration are independent.

My question is, I&#39;d like to minimise (if possible eliminate) heap allocated memory usage, as it at the moment is my largest performance problem.

Is there a way to convert a C string (char*) into a stl C++ string (std::string) without requiring std::string to internally alloc/copy the data?

Alternatively, could I use stringstreams or something similar to re-use a large buffer?

**Edit:** Thanks for the answers, for clarity, I think a revised question would be:

*How can I build (via multiple appends) a stl C++ string efficiently. And if performing this action in a loop, where each loop is totally independant, how can I re-use thisallocated space.*


initializing std::string from char* without copy

When programming in C++ in Visual Studio 2008, why is there no functionality like that seen in the refactor menu when using C#?


I use **Rename** constantly and you really miss it when it&#39;s not there. I&#39;m sure you can get plugins that offer this, but why isn&#39;t it integrated in to the IDE when using C++? Is this due to some gotcha in the way that C++ must be parsed?

  

Why is Visual C++ lacking refactor functionality?

I have a file of about 30000 lines of data that I want to load into a sqlite3 database. Is there a faster way than generating insert statements for each line of data?

The data is space-delimited and maps directly to an sqlite3 table. Is there any sort of bulk insert method for adding volume data to a database?

Has anyone devised some deviously wonderful way of doing this if it&#39;s not built in?

I should preface this by asking, is there a C++ way to do it from the API?



Faster bulk inserts in sqlite3?

I have a function called:

    void initializeJSP(string Experiment)

And in my MyJSP.h file I have:

    2: void initializeJSP(string Experiment);

And when I compile I get this error:

&gt;MyJSP.h:2 error: variable or field initializeJSP declared void

Where is the problem?

  



variable or field declared void

I need to find the smallest power of two that&#39;s greater or equal to a given value. So far, I have this:

    int value = 3221; // 3221 is just an example, could be any number
    int result = 1;

    while (result &lt; value) result &lt;&lt;= 1;

It works fine, but feels kind of naive. Is there a better algorithm for that problem?

EDIT. There were some nice Assembler suggestions, so I&#39;m adding those tags to the question.

Algorithm for finding the smallest power of two that&#39;s greater or equal to a given value

I&#39;m spending these holidays learning to write Qt applications. I was reading about Qt Designer just a few hours ago, which made me wonder : what do people writing real world applications in Qt use to design their GUIs? In fact, how do people design GUIs in general?

I, for one, found that writing the code by hand was conceptually simpler than using Qt Designer, although for complex GUIs Designer might make sense. Large GUIs might be possible using Designer, but with time they might become very difficult to manage as complexity increases (this is just my opinion). I also downloaded the AmaroK source code to take a peek at what those guys were doing, and found many calls to addWidget() and friends, but none of those XML files created by Designer (aside: AmaroK has to be my favorite application ever on any platform).

What, then, is the &quot;right&quot; way to create a GUI? Designer or code? Let us, for this discussion, consider the following types of GUIs :

1. Simple dialogs that just need to take input, show some result and exit. Let&#39;s assume an application that takes a YouTube URL and downloads the video to the user&#39;s hard disk. The sort of applications a newbie is likely to start out with.
2. Intermediate level GUIs like, say, a sticky notes editor with a few toolbar/menu items. Let&#39;s take xPad for example (http://getxpad.com/). I&#39;d say most applications falling in the category of &quot;utilities&quot;.
3. Very complex GUIs, like AmaroK or OpenOffice. You know &#39;em when you see &#39;em because they make your eyes bleed.

Hand Coded GUI Versus Qt Designer GUI

I just got a new quad core computer and noticed that nmake is only using 1 process.

I used to use make which had the switch -j4 for launching 4 processes.  What is the nmake equivalent?


[edit]
Based on the information below I have been able to add a command to my qmake project file:

QMAKE_CXXFLAGS += /MP

Which effectively did it for me.  Many thanks.

How do I utilise all the cores for nmake?

Qt documentation states that signals and slots can be `direct`, `queued` and `auto`. 

It also stated that if object that owns slot &#39;lives&#39; in a thread different from object that owns signal, emitting such signal will be like posting message - signal emit will return instantly and slot method will be called in target thread&#39;s event loop. 

Unfortunately, documentation do not specify that &#39;lives&#39; stands for and no examples is available. I have tried the following code:

**`main.h:`**

    class CThread1 : public QThread
    {
    Q_OBJECT
    public:
        void run( void )
        {
            msleep( 200 );
            std::cout &lt;&lt; &quot;thread 1 started&quot; &lt;&lt; std::endl;
            MySignal();
            exec();
        }
    signals:
        void MySignal( void );
    };
    
    class CThread2 : public QThread
    {
    Q_OBJECT
    public:
        void run( void )
        {
            std::cout &lt;&lt; &quot;thread 2 started&quot; &lt;&lt; std::endl;
            exec();
        }
    public slots:
        void MySlot( void )
        {
            std::cout &lt;&lt; &quot;slot called&quot; &lt;&lt; std::endl;
        }
    };


**`main.cpp:`**

    int main(int argc, char *argv[])
    {
        QCoreApplication a(argc, argv);
        CThread1 oThread1;
        CThread2 oThread2;
        QObject::connect( &amp; oThread1, SIGNAL( MySignal() ),
            &amp; oThread2, SLOT( MySlot() ) );
        oThread1.start();
        oThread2.start();
        oThread1.wait();
        oThread2.wait();
        return a.exec();
    }

Output is:

    thread 2 started
    thread 1 started

`MySlot()` is never called :(. What I&#39;m doing wrong?

How to emit cross-thread signal in Qt?

I have a Qt dialog application. Now I dont want that dialog to be resizeable. I am not sure how to achieve this. I tried a bunch of things but still when the dialog launches this dialog can be resized. 

What is the property that i should set to disable the dialog/Widget resize.

I also tried

    setSizePolicy(QSizePolicy::Fixed);

But i get an error saying.. 

&lt;pre&gt;
source\nimcac_settingsMain.cpp(36) : error C2248:
**&#39;QSizePolicy::QSizePolicy&#39; : cannot access private member declared in class &#39;QSizePolicy&#39;**
        p:\ThirdPartyExports\Qt\export\4.3\4.3.1f14\include\QtGui\../../src\gui\
kernel\qsizepolicy.h(177) : see declaration of &#39;QSizePolicy::QSizePolicy&#39;
        p:\ThirdPartyExports\Qt\export\4.3\4.3.1f14\include\QtGui\../../src\gui\
kernel\qsizepolicy.h(34) : see declaration of &#39;QSizePolicy&#39;
&lt;/pre&gt;

Kindly help me out with this.

Non-resizeable QDialog with fixed size in Qt?

How can I add external library into a project built by Qt Creator RC1 (version 0.9.2)? For example, the win32 function `EnumProcesses()` requires `Psapi.lib` to be added in the project to build.

Adding external library into Qt Creator project

I&#39;ve noticed that boost.asio has a lot of examples involving sockets, serial ports, and all sorts of non-file examples. Google hasn&#39;t really turned up a lot for me that mentions if asio is a good or valid approach for doing asynchronous file i/o.

I&#39;ve got gobs of data i&#39;d like to write to disk asynchronously. This can be done with native overlapped io in Windows (my platform), but I&#39;d prefer to have a platform independent solution.

I&#39;m curious if
   
 1. boost.asio has any kind of file support
 2. boost.asio file support is mature enough for everyday file i/o
 3. Will file support ever be added? Whats the outlook for this?


What&#39;s the deal with boost.asio and file i/o?

I was trying to build [Boost C++ Libraries][1] for last two hours and stopped without any result. Since I am new to C++, I am unable to get the build right. How can I build it correctly using Visual Studio 2008?

I need to use the BCP tool to extract a subset of library. So I need to build BCP first, right? How to do this? When I tried to build it, I got the following error

&gt; *fatal error LNK1104: cannot open file &#39;libboost_filesystem-vc90-mt-gd-1_37.lib&#39;.* 

Where can I get the above given library file?

  [1]: http://en.wikipedia.org/wiki/Boost_C%2B%2B_Libraries


Building Boost BCP

I have something like `shared_ptr&lt;Type&gt; t(makeSomething(), mem_fun(&amp;Type::deleteMe))`
I now need to call C styled function that requires a pointer to `Type`. How do I get it from `shared_ptr`?

getting a normal ptr from shared_ptr?

I dislike having magic boxes scattered all over my code...how exactly do these two classes work to allow basically any function to be mapped to a function object even if the function&lt;&gt; has a completely different parameter set to the one im passing to `boost::bind`

It even works with different calling conventions (i.e. member methods are `__thiscall` under VC, but &quot;normal&quot; functions are generally `__cdecl` or `__stdcall` for those that need to be compatible with C.

how boost::function and boost::bind work

Lots of the answers to C++ questions here contain the response:

&gt; &quot;You should be using boost::(insert
&gt; your favourite smart pointer here) or
&gt; even better boost::(insert your
&gt; favourite mega complex boost type
&gt; here)&quot;

I&#39;m not at all convinced that this is doing any favours to the questioners who, by and large, are obvious C++ novices. My reasons are as follows:

 - Using smart pointers without
   understanding what is going on under
   the hood is going to lead to a
   generation of C++ programmers who
   lack some of the basic skills of a
   programmer. Pretty much this seems to
   have happened in the Java field
   already.

 - Deciding which type of smart pointer
   to use depends very much on the
   problem domain being addressed. This
   is almost always missing from the
   questions posted here, so simply
   saying &quot;use a shared pointer&quot; is
   likely to be at the least unhelpful
   and possibly totally wrong.

 - Boost is not yet part of the C++
   standard and may not be available on
   the specific platform the questioner
   is using. Installing it is a bit
   painful (I just did it using [Jam][1]) and
   is way overkill if all you want are a
   few smart pointers.

 - If you are writing [FOSS][2] code, you
   don&#39;t want the code to be heavily
   dependent on external libraries that,
   once again, your users may not have.
   I&#39;ve been put off using FOSS code on
   a number of occasions simply because
   of the Byzantine complexity of the
   dependencies between libraries.

To conclude, I&#39;m not saying don&#39;t recommend Boost, but that we should be more careful when doing so.

  [1]: http://en.wikipedia.org/wiki/Perforce_Jam#Boost.jam
  [2]: http://en.wikipedia.org/wiki/Free_and_open_source_software


Content Type	Original Author	Original Content on Stackoverflow
Question	dwj	View Question on Stackoverflow
Solution 1 - C++	Martin Beckett	View Answer on Stackoverflow
Solution 2 - C++	Özgür	View Answer on Stackoverflow
Solution 3 - C++	Tiberiu Ana	View Answer on Stackoverflow
Solution 4 - C++	mxcl	View Answer on Stackoverflow
Solution 5 - C++	Daniel James	View Answer on Stackoverflow
Solution 6 - C++	Pietro	View Answer on Stackoverflow

Mixing Qt and Boost

C++ Problem Overview

C++ Solutions

Solution 1 - C++

Solution 2 - C++

Solution 3 - C++

Solution 4 - C++

Solution 5 - C++

Solution 6 - C++

How do I deal with quote characters when using cmd.exe

What are the most valuable .Net Compact Framework Tips, Tricks, and Gotcha-Avoiders?

Attributions