| To test whether QScreen properties are updated properly when the screen |
| actually changes, you will need to run some kind of control panel to make |
| changes, and this test program at the same time. E.g. on Linux, you can use |
| xrandr with various parameters on the command line, but there is also a nice |
| GUI called arandr which will probably work on any distro. Real-world users |
| would probably use the Gnome or KDE control panels, so that's also a good way |
| to test. On OSX you can make changes in System Preferences | Displays, and you |
| can also configure it to put a "monitors" icon on the menubar with a drop-down |
| menu for convenience. On Windows you can right-click on the desktop to get |
| display settings. |
| |
| Note that on Linux, if you have one graphics card with two outputs, typically |
| the two monitors connected to the outputs are combined into a single virtual |
| "screen", but each screen has multiple outputs. In that case there will be a |
| unique QScreen for each output, and they will be virtual siblings. The virtual |
| geometry depends on how you arrange the monitors (second one is to the right, |
| or above the first one, for example). It should be about the same if you are |
| using two graphics cards but using Xinerama to combine them. This test app will |
| create two windows, and will center one each screen, by setting the geometry. |
| |
| Alternatively you can configure xorg.conf to create separate screens for each |
| graphics card; then the mouse cursor can move between the screens, but |
| application windows cannot: each app needs to be started on the screen that |
| you want to run it on (by specifying e.g. DISPLAY=:0.1 for the second screen), |
| or the application has to set the desired screen via QWindow::setScreen() before |
| showing the window. |
| |
| The physical size of the screen is considered to be a constant. This can create |
| discrepancies in DPI when orientation is changed, or when the screen is |
| actually a VNC server and you change the resolution. So maybe |
| QScreen::physicalSize should also have a notifier, but that doesn't physically |
| make sense except when the screen is virtual. |
| |
| Another case is running two separate X servers on two graphics cards. In that |
| case they really do not know about each other, even at the xlib/xcb level, so |
| this test is irrelevant. You can run the test independently on each X server, |
| but you will just get one QScreen instance on each. |