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