std::async, and copies – gotcha!

Disclaimer: I love C++11! It’s the best thing that happened to C++ since I’m using it (mid-90’s). I’ve been hoping for lambda‘s in C++ since I discovered and started using Lisp. Elisions and move semantics – together with unique and shared pointers – pretty much free you from thinking about memory management! It’s just amazing! Check out “Going Native” talks on YouTube, incl. amazing talks by the likes of Stroustrup, Sutter, Lavavej, et al.

If you don’t want to read my rant, here’s the point – function objects are objects – they can get copied, unless you specify otherwise, so beware that you’re working on a copy, or pass std::ref.

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Get MainWindow in Qt Widgets

Update 2017/04/27 (thanks to grholk!):

The proper way would not be to check the objectName, which can change at any time, but rather to check if the widget is an instance of QMainWindow. Take advantage of what Qt makes available by using a foreach.

QMainWindow* getMainWindow()
    foreach(QWidget *widget, qApp->topLevelWidgets())
        if (QMainWindow *mainWindow = qobject_cast(widget))
            return mainWindow;
    return NULL;

Old version:

Provided how much you can do with Qt Widgets, or Qt in general, it’s no surprise that such “specialized” function is not present (the QApplication::activeWindow() does not make it, as the window might not be active).

#include <QApplication>
#include <QDateTime>

QMainWindow* getMainWindow()
    QWidgetList widgets = qApp->topLevelWidgets();
    for (QWidgetList::iterator i = widgets.begin(); i != widgets.end(); ++i)
        if ((*i)->objectName() == "MainWindow")
            return (QMainWindow*) (*i);
    return NULL;

If, for whatever reason, you changed the “objectName” property of the main window, update the above if with this name.

Automatic fclose() in C++11

This post is more of a mocking than serious advice, provided that a) STL includes <fstream> header with std::ifstream and std::ofstream classes, that do the same without any additional effort, and b) mixing templates and libC is just plain weird in my book. Continue reading

Command-line installation of OpenVPN

OpenVPN’s installer allows for command-line based (silent) installation, but this feature is not actually documented explicitly anywhere. Here’s all I could find – hope this list will help someone in the same situation I was in.

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Disable “New Tab Page” and “Smooth Scrolling” in FireFox

I really like FireFox 13+, it’s converging more and more towards Chrome(ium), with some neat details that will get into future versions of Chrome(ium).

Yet, there are two things I don’t like (just as I didn’t like them in Chrome) – the “new tab page” (“most visited”) and “smooth scrolling”.
“Smooth scroll” has been round for some time, but off by default. Now it’s on.

To get rid of both:

  • Open a new tab.
  • Type in about:config as URL. This will open FireFox’s geeky configuration. Accept responsibility for editing this stuff when opening for the first time.
  • Type newtabpage under “Search”, and double-click the “browser.newtabpage.enabled“; it will turn bold and it’s value (on the far right) will change to “false“. This will disable the “new tab page” – you can immediately check this by opening a new tab – it should be again charmingly empty.
  • Type smooth under “Search”, and double-click the “general.smoothScroll“; this will disable the smooth scrolling. Again, you can immediately check it out.

There are literally hundreds of settings under about:config that can change all of FireFox’s behaviour, up to breaking it inadvertently. Feel free to click around! 😉

Final rant – what the hell is going on with the version numbers? There are no more v4.5, or v4.5.2… FireFox and Chrome just switched to single digit versioning… AFAIC, they can call it “whatever is current version”, or just vInfinity…
IMO, it lowers the meaning of versioning per se – there is a reason for the minor (and subminor, …) versions – it means it’s essentially the same thing, with some improvements.
E.g. Chrome’s v16 – “multiple profiles on by default” is the major change… Or “style editor” in FireFox v11… that’s like saying that “cup holder made of aluminium instead of plastic” makes it a new model of a car!

The audacious’ problem “playlist_entry_get_filename assertion failed”

I’m very fond of audacious player (audacious2 to be precise) – light-weight, fast, and follows the WinAmp (2) path. Neat 🙂

Few days ago I’ve got the following error message on audacious start-up:

** (audacious2:2348): CRITICAL **: playlist_entry_get_filename: assertion `entry != NULL' failed
Segmentation fault

Reinstallation and re-configuration didn’t help; but the fix is quite trivial:

  • Start the audacious as root: $ sudo audacious2 ; this should work just fine, unlike when starting as normal user.
  • Add anything to the playlist, just so it’s not empty.
  • Close the player.
  • Now start the player as normal user; all should work now.

That’s it. Hope this helps!

Turn Your Box into a Dev Web Server

To turn your box into a dev web server is pretty simple, yet I’ve seen people struggling with this over and over again, so here’s a simple TODO list.

I won’t go over the likes of Apache installation, VirtualHost setup, .htaccess settings, etc. as you can find these online very easily, and might be specific to the needs of your project.

Most of the time I see people using localhost:8080 and a myriad of other ports to work on several sites locally; but you might as well work on locally in just 2 simple steps:

  • Create a VirtualHost in Apache which goes by “the name”, by including the following within the definition:
    <VirtualHost *:80>
        DocumentRoot /var/www/myproject/
        # all the other options and definitions ...
  • “Register” the domain name locally – simply add the following line to your /etc/hosts file (on Windows, this file is typically located under [Windows]/System32/Drivers/etc):

Now enable the VHost in Apache, restart Apache, and open in the browser, and you’re ready to code off!

Note: The VHost name need not be a valid domain name – feel free to use myproject as ServerName and in /etc/hosts; just beware that some browsers will try to search for “myproject” instead of opening the local site. In such case, type in the whole http://myproject.