Qt for Windows - Specific Issues

This page contains information about Qt for Windows.

Installation location

Installing Qt into a directory with spaces, for example, C:\Program Files, may cause linker errors like the following:

 c:\program.obj not found

Install Qt into a sub-directory without spaces to avoid this problem.

Maximum path length

The Win32 API that both Qt and compiler tools use has a built-in maximum file path length of 260 characters (MAX_PATH). This can hit you in various forms if either your absolute or relative directory structures are too verbose. It is therefore recommended to keep the file system paths within limits, and put build directories nearby the source directories.

Possible GL conflict

There is a known issue when running Microsoft NetMeeting, Lotus SameTime, and other applications that require screen grabbing while direct rendering is enabled. Other GL-applications may not work as expected, unless direct rendering is disabled.

Visual Studio

The Visual C++ Linker doesn't understand filenames with spaces (for example, C:\Program files\Qt\) so you will have to move it to another place, or explicitly set the path yourself.

 QTDIR=C:\Progra~1\Qt

If you are experiencing strange problems with using special flags that modify the alignment of structure and union members (such as /Zp2) then you will need to recompile Qt with the flags set for the application as well.

Fullscreen OpenGL Based Windows

When a window is using an OpenGL based surface and is appearing in full screen mode, problems can occur with other top-level windows which are part of the application. Due to limitations of the Windows DWM, compositing is not handled correctly for OpenGL based windows when going into full screen mode. As a result, other top-level windows are not placed on top of the full screen window when they are made visible. For example, menus may not appear correctly, or dialogs fail to show up.

A window can use an OpenGL based surface either explicitly when setSurfaceType() is called, or when something that requires OpenGL is used inside the window, causing the whole window to be OpenGL based. For example, QOpenGLWidget or QQuickWidget can trigger this. However, if the surface is contained in a QWindow which is hosted with createWindowContainer(), or the obsoleted QGLWidget is used and it does cover the entire full screen window, then this problem does not occur.

To solve this problem, a QWindowsWindowFunction can be used to enable a native Windows flag which will set WS_BORDER when showing in full screen mode. This can be utilized as follows:

 QWindowsWindowFunctions::setHasBorderInFullScreen(tlwWindow->windowHandle(), true);

This will give the full screen window a 1-pixel border, thus enabling the other top level windows to appear on top.