Tag Archives: Quick Tips

Quick Tip: Stay in Unity Play Mode while Coding

If you aren’t familiar with Unity, it’s a free game engine with a built-in game editor. I use Unity almost every day, and as you can imagine, I’m coding a lot. Now, when you are writing the majority of code for a game, you are testing things out. Perhaps you want to see how fast is fast enough, or how far is far enough. It can be a pain to enter and exit play mode constantly, but wait!

Unity has a nifty little feature that will recompile code and execute it, even while in play mode. You can easily switch over to Visual Studio (or MonoDevelop) and save your changes. Then you can “Alt + Tab” back over into Unity and quickly see your changes. The only downside to this is that, with large projects (10,000+ lines of C#), this can take a few seconds–even on a really fast machine. However, it’s invaluable when testing things, as you never have to leave your spot in play mode. 😉

Happy coding!


Quick Tip: Load Fonts from a Local File with QML

If you are familiar with CSS, you have probably loaded an external font before. With an Internet application, you usually wouldn’t load it from a file, but for a desktop application that doesn’t require an Internet connection, loading from a file is a must. Luckily, this is extremely easy and the TTF file can be embedded right in the executable using the Qt resource system (QRC protocol). In QML, there is a provided FontLoader element that makes quick work of loading fonts. Here’s quick example:

FontLoader { id: myCustomFont; source: "qrc:/fonts/myCustomFont.ttf" }

Note that if you want to do so, it is possible to directly link to a URL on the Internet. However, I wouldn’t recommend this unless you can ensure that your user will have an Internet connection at run-time. Otherwise, I would recommend downloading the TTF file instead and putting it in a local resource file. Be sure to read the license before doing this though!

When you want to use the font later in a font field, for example, you can simply do:

font.family: myCustomFont.name

And that’s it! You are all set to use custom Truetype Fonts in QML! I hope this helps you out with your QML application. Happy coding!

Quick Tip: QProgressBar as a Busy Indicator

This is a super simple tip that doesn’t really have much to it. A busy indicator is just a visual cue to show the user that something is happening. To use a progress bar in Qt as one, you just need to set the minimum and maximum values to 0. If you do this, you get an infinite progress indicator. This is a better alternative to a progress bar when you have a process in which you cannot calculate the percentage completed, or one that takes a really long, undetermined, amount of time. An example with the Fusion style (that I use for basically any QWidgets these days) yields an animated diagonal stitch pattern:

Busy Progress Bar

The Qt Fusion style progress bar.

On Windows 7, you get a nice animated effect as well, but with a smaller colored area moving from left to right infinitely.

Windows 7 Busy Progress Bar

The Windows 7 version of the busy progress bar indicator

I hope the tip helped you out! Happy coding!

Quick Tip: Copy a QPixmap to the System Clipboard in Qt

A few days ago, we went over copying any amount of text to the system clipboard using the system clipboard. However, you can also leverage the full-power of this by copying images and pixmaps to the system clipboard. Let’s get started!

Example UI with Pixmap

Our example UI for this. Simply set a pixmap on a label. along with a button.

Behold my stunning UI for this example. 😛 Now that you have your GUI setup, go to the push button’s slot (or wherever you want to put the code) and you are left with this:

    QClipboard *p_Clipboard = QApplication::clipboard();

This is essentially what we did with text, however, with a different method. Note the dereference of the constant pointer we get to the label’s pixmap. This is essential, because the setPixmap() function wants a QPixmap object (taken by reference, not pointer). How can you not love C++? 🙂

Then you can paste it anywhere that lets you insert images through the paste!

The image pasted in MS Word

Here’s the copied pixmap pasted into Word. You can also paste it elsewhere, as long as the form accepts images from the clipboard.

And that about wraps it up. I hope you can use this in one of your projects, and share it if it was useful. Happy coding!

Quick Tip: Copy Any Text to the System Clipboard in Qt

Now, this is a super quick tip, as it’s really a no-brainer. The explanation (if you need one) is that a QApplication has a global instance of the clipboard, which can be accessed by simply getting a pointer to it. So lets just get to the code!

    QClipboard *p_Clipboard = QApplication::clipboard();

And viola! Just like that, your text should now be on the system clipboard. Happy coding!

Quick Tip: Qt 5 Standard Paths

In Qt 5, the way you retrieve standard paths for a system has changed. Now, you use a special class named QStandardPaths instead of the desktop services class. By far my favorite use for this is locating directories without user interaction. In this quick example, we’ll locate the user’s home directory. Note that you can use any of the provided enums in replace of QStandardPaths::HomeLocation.

QString homeLocation = QStandardPaths::locate(QStandardPaths::HomeLocation, QString(), QStandardPaths::LocateDirectory);

This will return C:/Users/Admin on my development PC. This should work cross platform as well, so no more fiddling with the preprocessor to decide which default location to use. 🙂 You can replace the QString() with additional details for location.

Quick Tip: Using Multiple UI Files in a Qt Application

This is way easier than I first realized with Qt. If you are having troubles figuring this out, do not look any further! Now, it seems I make a habit of trying to figure out how to do things in Qt without consulting my C++ 101 chapters in all those books I read a long time ago. 😛 Every form is a class, (e.g. mainwindow.h/mainwindow.cpp), and if you look in your main function… what does it do? Of course! It just creates an instance and shows it! That easy! Now, there are a few things you can do, but this is the gist of it:

    AboutDialog *aboutDialog = new AboutDialog(this);
    aboutDialog->setAttribute(Qt::WA_DeleteOnClose, true);

Now, this is just some code that I generally use to show a custom about dialog. The main parts you should note are line 1 and 4. On line 1, we instantiate a pointer to an AboutDialog (be sure to include the header file). We use a pointer because, well, if you try using a scoped object, it usually [always] doesn’t work. The dialog simply will disappear because the object is destroyed when it goes out of scope. (Note: this works in main because you have the event loop, i.e. app.exec()).

The middle 2 lines are simply “parameters” I’ve set for this particular dialog. The 2nd line just makes it so the pointer is deleted on closing the dialog. You might not want this if you are using a dialog with data you store in its members. That’s common of a non-modal dialog in my experience. The 3rd line sets the fixed size. This is actually one way to do this, and you can find a plethora of other ways to set a fixed size for your dialog.

The 4th line is rather interesting, as you can change how a window is opened by using either open() or show(). They both yield different results. Basically, open() is just going to open the dialog as a modal dialog, whereas show() is more appropriate for something that’s going to have a longer life-span in the application. I encourage you to play around with this, as it will truly add another layer of depth if you are trying to cram everything into one form! 😉