Here is the way to change keyboard shortcuts in Lubuntu https://help.ubuntu.com/community/Lubuntu/Keyboard#Create_New_Keyboard_shortcuts
Open lubuntu-rc.xml
in your favorite editor.. (Mine its vim, it could be leafpad/vi/nano )
`sudo vim ~/.config/openbox/lubuntu-rc.xml`
then find the following code..
<keybind key="Print">
<action name="Execute">
<command>lxsession-default screenshot</command>
</action>
</keybind>
Comment out <command>lxsession-default screenshot</command>
and add <command>shutter -f</command>
.. (or just you can replace, instead of commenting, but I prefer doing so)
<keybind key="Print">
<action name="Execute">
<!-- <command>lxsession-default screenshot</command> -->
<command>shutter -f</command>
</action>
</keybind>
And also you can replace ( Alt + Print ) option by changing to this shutter -a in the following manner..
<keybind key="A-Print">
<action name="Execute">
<!--<command>lxsession-default screenshot window</command> -->
<command>shutter -a</command>
</action>
</keybind>
Then reload openbox
openbox --reconfigure
Rest are same as this
Then open shutter and go to menu (Edit--->preference--->main
)
Select Do not save file automatically
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At this point you have achieve main screen by pressing printscreen button or Alt + printscreen button..
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To open edit windows, instead of main screen, when ressing printscreen button or Alt + printscreen button, go to Actions in preference and select open with Built-in Editor
And make sure other settings remain as below in behavior section,
Done!!