在Ubuntu 16.04中，通过右键单击扩展坞上的屏幕快照应用程序，可以选择“对选定区域进行屏幕快照”。
在Ubuntu 18.04中，此选项已消失...
如何还原它？
org.gnome.Screenshot.desktop文件包含：
[Desktop Entry]
Name[en_GB]=Screenshot
... other translations
Name=Screenshot
Comment[en_GB]=Save images of your screen or individual windows
... other translations
Comment=Save images of your screen or individual windows
Keywords[en_GB]=snapshot;capture;print;screenshot;
... other translations
Keywords=snapshot;capture;print;screenshot;
Exec=gnome-screenshot --interactive
Terminal=false
Type=Application
Icon=applets-screenshooter
StartupNotify=true
Categories=GTK;GNOME;Utility;X-GNOME-Utilities;
NotShowIn=KDE;
X-GNOME-Bugzilla-Bugzilla=GNOME
X-GNOME-Bugzilla-Product=gnome-utils
X-GNOME-Bugzilla-Component=screenshot
# Disable broken actions https://pad.lv/1720262
# Actions=screen-shot;window-shot;area-shot
Actions=screen-shot;
DBusActivatable=true
[Desktop Action screen-shot]
Name[en_GB]=Take a Screenshot of the Whole Screen
... other translations
Name=Take a Screenshot of the Whole Screen
Exec=gnome-screenshot
[Desktop Action window-shot]
Name[en_GB]=Take a Screenshot of the Current Window
... other translations
Name=Take a Screenshot of the Current Window
Exec=gnome-screenshot -w
[Desktop Action area-shot]
Name=Take a Screenshot of a Selected Area
Exec=gnome-screenshot -a