linux separate screen configuration issue

[sebastien deries]

Greetings,

I develop an application on linux  on a Red Hat 6.8 x64 using java 8u162
and an NVidia GPU (and its latest driver), with 2 full HD Screens.

I got an issue retrieving the number of physical screens:

   - when the X server is in extended desktop mode (2 physical screens, but
   a single logical one from 0 to 3840 pixels), Screen.getScreens() returns 2
   Screen (which is normal)
   - When the X server is in separate desktop mode (2 physical screens and
   2 logical screens from 0 to 1920 pixels), Screen.getScreens() returns 1
   Screen ==>  is this normal or a bug?

I compared the JavaFX API to the AWT API:

GraphicsEnvironment env = GraphicsEnvironment.getLocalGraphicsEnvironment();
GraphicsDevice[] gdev = env.getScreenDevices();

AWT returns 2 screen devices in both configuration mode.


I Also checked on java 9 and java 10 using a ubuntu x64 machine and got the
same issue with JavaFX.

I tried debugging this and it seems that the issue is in libglass.so in
native code.

What do you think about this ?

Thank you for your help.

Regards

Sebastien


Here is the code that reproduces the issue:

public class ScreenTest extends Application {

    private static final int SIZE = 1600;
    private final AnchorPane root = new AnchorPane();

    @Override
    public void start(Stage primaryStage) throws Exception {

        root.backgroundProperty().set(new Background(new
BackgroundFill(Color.BEIGE, null, null)));
        Scene scene = new Scene(root, SIZE, SIZE);
        primaryStage.show();

        Screen.getScreens().forEach(screen -> System.out.println("JAVAFX :"
+ screen));
        GraphicsEnvironment env =
GraphicsEnvironment.getLocalGraphicsEnvironment();
        GraphicsDevice[] gdev = env.getScreenDevices();

        for (GraphicsDevice d : gdev) {
            System.out.println("AWT:" + d);
        }
    }
    public static void main(String... strings) {
        launch(strings);
    }
}



here is the X11  Xorg.conf:

Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "Screen0" 0 0
    Screen      1  "Screen1" RightOf "Screen0"
    InputDevice    "Keyboard0" "CoreKeyboard"
    InputDevice    "Mouse0" "CorePointer"
    Option         "Xinerama" "0"
EndSection

Section "Files"
EndSection

Section "InputDevice"

    # generated from default
    Identifier     "Mouse0"
    Driver         "mouse"
    Option         "Protocol" "auto"
    Option         "Device" "/dev/psaux"
    Option         "Emulate3Buttons" "no"
    Option         "ZAxisMapping" "4 5"
EndSection

Section "InputDevice"

    # generated from default
    Identifier     "Keyboard0"
    Driver         "kbd"
EndSection

Section "Monitor"
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "CMN"
    HorizSync       53.0 - 66.0
    VertRefresh     48.0 - 60.0
    Option         "DPMS"
EndSection

Section "Monitor"
    Identifier     "Monitor1"
    VendorName     "Unknown"
    ModelName      "DELL C7017T"
    HorizSync       30.0 - 83.0
    VertRefresh     56.0 - 76.0
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "Quadro K3100M"
    BusID          "PCI:1:0:0"
    Screen          0
EndSection

Section "Device"
    Identifier     "Device1"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "Quadro K3100M"
    BusID          "PCI:1:0:0"
    Screen          1
EndSection