How to Be Cute on All Desktops with Qt

Using Platform-Specifics through a Movable API

Qt might provide a cross-platform API that can cover almost all cases, but you still might want to use platform-specific features. For instance, opening the window as maximized in Windows and normal on OS X and X11. To handle these situations, Qt provides preprocessor defines describing on which OS you are running and which windowing system you are using. For example, on Linux, you'll find Q_OS_LINUX and probably Q_WS_X11.

When you know on which system you are running, you can access all X11 events by re-implementing the x11EventFilter function of the QApplication class. On OS X, you can get hold of the CoreGraphics handle from the macCGHandle function of each QWidget.

If you want to avoid writing platform-specific code, you still can give platform-specific hints. For instance, you can give a hint to a QDialog that it is a sheet. This is a dialog that appears inside another window or dialog that provides part of the larger window's features. You do this by setting the window flags of your dialog to Qt::Sheet.

On X11, this type of hint relies on the window manager's ability to understand it. This means the hint must be used as a hint, not a setting. If you want complete control, pass Qt::X11BypassWindowManagerHint. This tries to avoid the window manager completely, which is not a nice thing to do, but might be necessary.

Cross-Platform Development Using a Cross-Platform Environment

Qt comes with a set of tools that can be used separately or from within the fairly new QtCreator application. QtCreator was created using Qt and provides an advanced code editor, documentation, an integrated version of Qt Designer and editors for Qt-specific files, such as project files and resource files.

Because all the Qt tools also are available separately, it is common to use another IDE or just a text editor and command line. Qt Software provides integrations for Microsoft Visual Studio, Xcode and Eclipse. There also are a range of free IDE projects out there, such as Edyuk, QDevelop and KDevelop.

So, what does QtCreator provide that the others don't? First, it comes as a part of the Qt SDK. The SDK version of Qt comes as a single download with a prebuilt version of Qt and QtCreator set up and ready to go. Second, it provides a graphical debugger interface, letting you use gdb in the easiest possible manner across all desktop platforms supported by Qt. The debugger knows of Qt and provides macros for easy viewing of QString objects as well as for looking inside Qt's list classes.