Category: Qt

Here’s a demo of “real” 3D in pure Qt. It doesn’t rely on third party 3D libraries like OpenGL, DirectX, or even Qt’s own convenience class QTransform. It’s actually very simple. It uses a very simple trigonometry function for rotating a point you can get off of Wikipedia. Everything else has to be calculated manually, but it works. The geometry is accurate. But so far this is only a work-in-progress and I haven’t quite figured out the texture mapping. But the fact that the faces can have textures mapped to them, yes with QTransform, means it’s ready for Mode 7 if you just want to put up single plane “sprites” as obstacles in an F-Zero or Mario Kart-like game. But I want to have full 3D boxes or buildings or platforms.

So we’ll see. It’s all a learning process for me.

The Phonon documentation provided by Qt isn’t thorough because Qt stopped providing support for it after awhile. So you’ll have to do extensive scouring of the Internet to make even your most basic Phonon app work. Here’s how:

When you’re coding, you can add the #includes, but you’ll notice the compiler may give errors. That’s because you have to dig pretty deep in the Phonon documentation provided by Qt in order to find out how to use their moc system. So make sure you add:

Qt += phonon

to the line in your QCreator *.pro file before you compile your application.

So when it’s time to deploy, make sure when you distribute your Phonon-based application to copy these folders to be distributed with your final Windows self-executable (*.exe format), which can be found in your Qt 4.8.7 installation folder %Qt%/plugins/

/phonon_backend
/codecs

You’ll also need the following DLLs to be distributed too, so copy them from Qt installation folder %Qt%/bin/

-QtDBus4.dll
-QtXml4.dll
-phonon4.dll

So once these folders and files have been distributed with your Windows self-executable, you should be able to play basic media files such as WAV and AVI formats. Other formats like MPG, MP3, MP4, AAC, MIDI, WMV, MOV, OGG, FLV may require additional codecs and programming. But the only way you’ll know for sure is to test them. Otherwise stick with formats you know for sure Windows (or your target deployment operating system) supports.

Hope that helps!

Upgrading to Qt 4.8.7 on Windows

By Chongchen Saelee

I’m upgrading from Qt 4.8.5 to Qt 4.8.7. I’m also using QtCreator 2.8.0. This a step-by-step guide on how I successfully upgraded.

NOTE: Qt 4.8.7 requires newer minGW 64 compiler, so if you don’t install that correctly, it won’t work. Qt 4.8.7 SDK Installer does not come with minGW 64 compiler, so you have to download that separately. Continue reading “Upgrading to Qt 4.8.7 from Qt 4.8.5”

Don’t get me wrong, I love Qt, but they do make the disclaimer when you download and use their software. Just note that unless you have money to burn, if you keep pushing the limits of your hardware and operating system, odds are Qt will make it all crash and burn. For example, I’ve been able to compile and run “simple” programs endlessly without a problem. But once I start experimenting with QTransform or other heavy image processing things, my harddrive goes on the fritz or memory issues or graphics card chugs. It’s just not worth it if I have to replace these hardware. Therefore, just to put it out there for the hobbyists who might be curious: DO NOT RISK HAVING TO REPLACE YOUR HARDWARE BY EXPERIMENTING WITH QTRANSFORM OR QIMAGE IF, that’s IF YOU’RE GOING TO PUSH THE SYSTEM WITH 3D PROCESSING.

Mind you, that’s only if you’re messing with 3D stuff. You can mess with QPixmap and QImage for 2D stuff, but don’t mess with QTransform or QImage when it comes to 3D. It’s just too brutal on my hardware. I think it has to do with the nature of how Qt is designed: to do everything as fast as possible. And I’m assuming that include “unsafe” methods. I recall working with DirectX a bit and that’s why Microsoft wants you to use their “safe” DirectX functions vs “unsafe”, even though unsafe methods may yield faster results.

And I’m developing on a Windows 7, Pentium i5 3.4GHz Quad Core processor, new hard drive, new RAM, the works. So just be extra careful and aware. It’s not maliciously designed, it’s like that for a reason. Machine cannot regulate itself and always needs human intervention.

You can embed a True Type font or Open Type font into your Qt application using QFontDatabase. You can link to an external font file or link to a font embedded as a resource.

First, make sure you include a reference to the QFontDatabase class:

#include <QFontDatabase>;

To link to an external font, do this:

QFontDatabase database;
int result = database.addApplicationFont("/path/to/font.tff");

Or for a more reliable way, embed the font as a resource. Create a Qt resource file and add a reference to the font file you want embedded. Then use the path to the embedded resource font:

QFontDatabase database;
int result = database.addApplicationFont(":/resource/path/to/font.tff");

If the returned integer is greater than -1, then the font has successfully loaded into the font database. It’s essentially storing the font in memory at the application’s runtime. You can check your operating system’s installed fonts and if the font hasn’t already been installed, that using QFontDatabase doesn’t install the font on your system. So this is a cool way of having specific fonts just for your Qt app without messing with the end-user’s fonts.

And to use the font, you would call it from the font database:

QFont f = database.font("myFont", "normal", 12);
myWidget.setFont(f);

Of course, be mindful of the font you choose for your app. As graphic designers, we are taught that for digital screens, you want to use sans-serif fonts (vs serif fonts for print). There needs to be good whitespace. Since users will be staring at the fonts for long periods of time, it needs to look nice and balanced overall. Then there’s also the issue of visual consistency and compatibility across operating systems. In this case, you don’t have to embed a custom font, but make sure you choose a web-safe font.

You can mix any color you want nowadays with 32-bit colors. But sometimes, it’s just so much more convenient if the color palette already exists. And unfortunately, Qt only provides users with the most basic of colors. Therefore, it’s up to you to come up with a snazzy pre-mixed color palette yourself, but also to name those custom colors. But you don’t need to reinvent the wheel. The X Windows system and W3 web standard for colors and names already exists.

Unfortunately, if you’re using Qt on Windows, you won’t be able to access that color palette.

So this is what I did: I simply took the names and RGB values and created a wrapper class in Qt. That way I can easily access the colors via their names. Ain’t that a trip? It seems so simple to implement, but I haven’t found any tutorials out there on the Interwebs. It could save a lot of time for those that deal with a lot of colors.

Also, I whipped up a quick demo that displays the colors all nice and purdy.

Feel free to use this X11 color name wrapper class in your Qt project. Enjoy!

You can download the Qt 4.8.5 project files here:
X11_colors_qt

If you were unaware that Qt’s default mouseDoubleClickEvent isn’t exactly optimized, as that is the nature of the beast, so when you override it, it will slow everything down. So the only thing you can do is write your own mouse double click event handler.

I won’t be using custom events and any fancy delegates and stuff. Don’t touch system pointers or direct memory unless you have to. This is a very simple implementation compared to the big picture.

To begin, you must understand that a mouse double click is essentially this sequence: mousePress, mouseRelease, mouseDoubleClickFlag, mouseRelease. Continue reading “How to Implement Custom Optimized MouseDoubleClickEvent Function in Qt”

http://qt-project.org/doc/qt-4.8/qwidget.html#mouseDoubleClickEvent

I just discovered this. I’ve been implementing the convenience overriding of MouseDoubleClickEvent in all of my custom widgets. After optimizing all of my basic overrided mouse handling events: mousePressed, mouseMove, mouseReleased, it turns out it was that dang doubleclick that slowed it all down in the end. And all this time I thought I hadn’t written a tight optimized rendering loop.

Anyway, BE VERY CAREFUL with this. As it states in the reference documentation:

Note: The widget will also receive mouse press and mouse release events in addition to the double click event. It is up to the developer to ensure that the application interprets these events correctly.

That means that if you already have all your mousePress and mouseRelease custom overriding functions implemented, those will get called multiple times before it gets to the new override implementation of doubleclick, which will slow everything down exponentially. That doesn’t mean it’s a bug, that’s technically how a double-click is implemented at the internal level.

It looks like the only way to get optimal performance is to implement double-click yourself with a timer or variable.

Well, damn.

If you, too, are scouring the Interwebs for the answer, here it is:

http://www.qtforum.org/article/30063/qt-opengl-resolution.html?s=404deefd560e1ab54cce082517049711d0fdb836#post100696

First, you’re going to need to download the Windows SDK to get the proper c++ header files to reference. In this particular case, you’re going to want to reference “windows.h” like so:

#include "windows.h"

And then access the ChangeDisplaySettings function from the Windows API like so: Continue reading “How to change screen resolution in Windows using Qt”