qt 支持双屏显示，网上应该是一大堆，你可以随便百度！

但是关于qt5 支持双屏幕显示的资料甚少， 现将其记录下来：

让我们引用一段经典的文章吧：

Multiple screens

When having multiple displays connected (e.g. the touch LCD panel and HDMI), there are two framebuffer devices: /dev/fb0 and /dev/fb2. Note that fb1 and fb3 are overlays for fb0 and fb2 and are not useful for our purposes here.

Both eglfs and linuxfb uses /dev/fb0 by default. To change this, linuxfb can be configued with the 'fb' parameter: just launch the application with "-platform linuxfb:fb=/dev/fb2".

eglfs has no way to configure this before 5.3.0 so apps using eglfs will always show up on the display belonging to fb0. In 5.3.0 a new environment variable is introduced: QT_QPA_EGLFS_FB. Setting this to /dev/fb2 before launching the app will make the EGL/GLES content show up on the second display.Update: It might be possible to launch eglfs apps on the other display with 5.2 too, by setting FB_FRAMEBUFFER_0 to /dev/fb2.

There is currently no way to display content on multiple displays from the same application. The workaround is to launch two separate applications and use some sort of IPC mechanism to communicate between them.

Screen configuration

Both linuxfb and eglfs will try to query the display dimensions (both physical and pixels) from the framebuffer device. This may not always lead to good looking results. For eglfs the screen size can be set explicitly by setting QT_QPA_EGLFS_WIDTH and QT_QPA_EGLFS_HEIGHT to the desired width/height (in pixels) before launching the application. linuxfb has a size=…x… plugin parameter (for example -platform linuxfb:fb=/dev/fb2:size=1920x1080).

已经很精辟了，不需要我再多言了。