Screen goes black when attempting to select a region

[era]

When I select "Screenshot" from the Accessories menu and click "Select a region", the screen goes black. The only thing I see is a crosshair cursor.

I can just blindly click and drag the crosshairs across the approximate region which was visible when I started, and then the screen goes back to normal. The actual screenshot will show the reappeared contents of the region I selected.

I have a moderately complex triple-screen setup. Xrandr is not working on this rig. There are two nvidia display cards, one of which drives two larger monitors, and the second drives a smaller one. I use a recent restricted nvidia driver.

$ apt-cache policy xfce4-screenshooter
xfce4-screenshooter:
  Installed: 1.8.0-2
  Candidate: 1.8.0-2
  Version table:
 *** 1.8.0-2 0
        500 http://fi.archive.ubuntu.com/ubuntu/ precise/universe amd64 Packages
        500 http://mirrors.nic.funet.fi/

$ dpkg -l *nvidia*
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Description
+++-==============-==============-============================================
un libgl1-nvidia- <none> (no description available)
un nvidia-180-mod <none> (no description available)
un nvidia-185-mod <none> (no description available)
ii nvidia-common 1:0.2.44.2 Find obsolete NVIDIA drivers
un nvidia-current <none> (no description available)
ii nvidia-experim 310.14-0ubuntu Experimental NVIDIA binary Xorg driver, kern
ii nvidia-setting 310.14-0ubuntu Tool for configuring the NVIDIA graphics dri

$ apt-cache policy nvidia-experimental-310
nvidia-experimental-310:
  Installed: 310.14-0ubuntu0.3
  Candidate: 310.14-0ubuntu0.3
  Version table:
 *** 310.14-0ubuntu0.3 0
        500 http://fi.archive.ubuntu.com/ubuntu/ precise-updates/restricted amd6
4 Packages
        500 http://mirrors.nic.funet.fi/ubuntu/ precise-updates/restricted amd64
 Packages
        100 /var/lib/dpkg/status

$ cat /etc/X11/xorg.conf
# nvidia-settings: X configuration file generated by nvidia-settings
# nvidia-settings: version 310.14 (buildd@komainu) Tue Oct 16 22:20:47 UTC 2012

Section "ServerLayout"
    Identifier "Layout0"
    Screen 0 "Screen0" 1680 0
    Screen 1 "Screen1" LeftOf "Screen0"
    Screen 2 "Screen2" RightOf "Screen1"
    InputDevice "Keyboard0" "CoreKeyboard"
    InputDevice "Mouse0" "CorePointer"
    Option "Xinerama" "1"
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"
    # HorizSync source: edid, VertRefresh source: edid
    Identifier "Monitor0"
    VendorName "Unknown"
    ModelName "DELL P2412H"
    HorizSync 30.0 - 83.0
    VertRefresh 56.0 - 76.0
    Option "DPMS"
EndSection

Section "Monitor"
    # HorizSync source: edid, VertRefresh source: edid
    Identifier "Monitor1"
    VendorName "Unknown"
    ModelName "DELL 2007WFP"
    HorizSync 30.0 - 83.0
    VertRefresh 56.0 - 76.0
    Option "DPMS"
EndSection

Section "Monitor"
    # HorizSync source: edid, VertRefresh source: edid
    Identifier "Monitor2"
    VendorName "Unknown"
    ModelName "DELL 2007WFP"
    HorizSync 30.0 - 83.0
    VertRefresh 56.0 - 76.0
    Option "DPMS"
EndSection

Section "Device"
    Identifier "Device0"
    Driver "nvidia"
    VendorName "NVIDIA Corporation"
    BoardName "NVS 300"
    BusID "PCI:3:0:0"
EndSection

Section "Device"
    Identifier "Device1"
    Driver "nvidia"
    VendorName "NVIDIA Corporation"
    BoardName "NVS 300"
    BusID "PCI:4:0:0"
    Screen 0
EndSection

Section "Device"
    Identifier "Device2"
    Driver "nvidia"
    VendorName "NVIDIA Corporation"
    BoardName "NVS 300"
    BusID "PCI:4:0:0"
    Screen 1
EndSection

Section "Screen"
    Identifier "Screen0"
    Device "Device0"
    Monitor "Monitor0"
    DefaultDepth 24
    Option "Stereo" "0"
    Option "nvidiaXineramaInfoOrder" "DFP-0"
    Option "metamodes" "DFP-0: nvidia-auto-select +0+0, DFP-1: nvidia-auto-select +1920+0"
    SubSection "Display"
        Depth 24
    EndSubSection
EndSection

Section "Screen"
    Identifier "Screen1"
    Device "Device1"
    Monitor "Monitor1"
    DefaultDepth 24
    Option "Stereo" "0"
    Option "metamodes" "DFP-0: nvidia-auto-select +0+0; DFP-0: nvidia-auto-select +0+0; DFP-0: 1680x1050 +0+0; DFP-0: 1680x1050_60 +0+0; DFP-0: 1280x1024 +0+0; DFP-0: 1280x1024_75 +0+0; DFP-0: 1280x1024_60 +0+0; DFP-0: 1152x864 +0+0; DFP-0: 1152x864_75 +0+0; DFP-0: 1024x768 +0+0; DFP-0: 1024x768_75 +0+0; DFP-0: 1024x768_60 +0+0; DFP-0: 800x600 +0+0; DFP-0: 800x600_75 +0+0; DFP-0: 800x600_60 +0+0; DFP-0: 640x480 +0+0; DFP-0: 640x480_75 +0+0; DFP-0: 640x480_60 +0+0; DFP-0: nvidia-auto-select +0+0; DFP-0: nvidia-auto-select +0+0"
    SubSection "Display"
        Depth 24
    EndSubSection
EndSection

Section "Screen"
    Identifier "Screen2"
    Device "Device2"
    Monitor "Monitor2"
    DefaultDepth 24
    Option "Stereo" "0"
    Option "metamodes" "DFP-1: nvidia-auto-select +0+0"
    SubSection "Display"
        Depth 24
    EndSubSection
EndSection

Section "Extensions"
    Option "Composite" "Disable"
EndSection

[i (iiiiii-deactivatedaccount)]

If we enable compositing in xfwm4 when we run 'xfce4-screenshooter -r' the screen becomes black and so we can't select the region for the screen-shot properly (specially since the region can't be moved after selection as the screen-shot is taken on button release).
I've tried playing a bit with the compositor settings but it didn't change this behaviour.

So the black background could have instead a reasonable transparency by default. Something like 25% opacity.

Name : xfce4-screenshooter
Version : 1.8.0
Release : 7.fc18
Architecture: i686

[Jeromeg (jeromeg)]

Current transparency is 80%, but I also noticed when testing the latest Xubuntu release that it is not very usable on dark backgrounds.

I'll see if lowering the value helps. Being able to modify the selection has been on my planning but I don't know when/if I'll get to it.

[i (iiiiii-deactivatedaccount)]

As a workaround, how about lowering opacity to 25% (or if you feel it's too transparent, maybe max 40%)?

I use a CRT monitor and I notice it has bad contrast in the dark region or maybe the issue is that the glass of the screen reflects light.

Running 'xfce4-screnshooter -r' in this same page I can see it through but I have to look close for that.

[i (iiiiii-deactivatedaccount)]

I've build it from source here changing 0.8 to 0.4 in xfce4-screenshooter/lib/screenshooter-capture.c

lines 525-526:
          /* Restore the transparent background */
          cairo_set_source_rgba (cr, 0, 0, 0, 0.8);

lines 549-551:
      /* Draw the transparent background */
      cr = gdk_cairo_create (GDK_DRAWABLE (widget->window));
      cairo_set_source_rgba (cr, 0, 0, 0, 0.8);

And it's very usable this way.

[Jeromeg (jeromeg)]

Ok, I'll get to this when I have access to my development computer. Meanwhile, you could get a patch ready (see git format-patch).

[i (iiiiii-deactivatedaccount)]

Created attachment 4780
Increase background transparency for selection screenshot.

It's working for me but since I'm not a programmer I don't know if anything else should be changed.

[Jeromeg (jeromeg)]

Pushed patch to git master branch, thanks a lot for your contribution!

[era (era)]

I tested in a VMware image and noticed that it turns down the screen brightness, but not all the way to zero. I guess something in my display setup prevents it from turning it down partially (the lack of composite support?) but in this case, it should not try to turn it down at all, IMHO.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[js1 (sujiannming)]

Same problem on xubuntu 14.04.2:

ii xfce4-screenshooter 1.8.1-2ubuntu1

Using AMD's fglrx. Packaged fglrx does not support my video card yet.

[js1 (sujiannming)]

The problem does seem like screenshooter dims the entire screen down way too much.

[Theo Linkspfeifer (lastonestanding)]

=== Version 1.8.2 ===

  * Enhancements:
    - Add imgur.com as possible upload option (bug #6899)
    - Add appdate file (bug #11202)
    - Make region selection with compositing on more usable on darker
      backgrounds (bug #9592).
    - Updated translations (thanks to translators!)

  * Bugs fixed:
    - Fix keyboard navigation between choices (bug #11325)
    - Fix build with automake 1.13 (bug #10030)
    - Use filename-friendly date format for saved files (bug #8445)