/dev/blog

The button that is supposed to toggle the ambient light sensor on HP EliteBooks 8440p and 8460p per default switches off the touch pad. That is because Fn+F11 (scancode 0x33), which is the ambient light button, is incorrectly mapped to KEY_TOUCHPAD_OFF (keycode 193) in kernel.

To remap the scancode to another keycode, you can use setkeycodes. An appropriate choice for a target keycode could be KEY_PROG1 (XF86Launch1, keycode 148) which can be easily reconfigured in KDE or any other desktop environment to run any custom command.

Run the following command as root to remap Fn+F11 to KEY_PROG1:

# setkeycodes e033 148

Resources:
http://www.linlap.com/hp_elitebook_8460p

While you can normally insert arbitrary unicode characters to any X11 application using Ctrl-Shift-u and four hex digits, it doesn’t work in kwrite or kate. Instead you’d have to press F7 to switch to command line and type in

char <unicode>

For example, to get the degree symbol (Unicode: U+00B0) you’d type in 'char 176' (176 being 0xB0 converted do decimal).

With the release of Fedora 18, there have been some changes to the /etc/sysconfig directory. For example, switching the default display manager is no longer done by altering parameters in /etc/sysconfig/desktop but via

# systemctl enable --force displaymanager.service 

Therefore, to switch from the default gdm to kdm you’d run:

# systemctl enable --force kdm.service 

There are quite a few bug reports on the kde bug tracking system about kde losing display settings on logout (e.g. Bug 183143). But since this problem has been present for a couple of years and is still existing in the latest version of KDE (i.e. 4.8.5 at this writing), here’s a workaround:

Add a parameter called StartupCommands to the krandr configuration file (usually located at ~/.kde/share/config/krandrrc that adjusts your display layout using xrandr on login:

[Display]
ApplyOnStartup=true
StartupCommands=xrandr --output "HDMI-0" --primary --output "VGA-0" --right-of "HDMI-0"

You also need to make sure that the command is invoked on login by setting the ApplyOnStartup parameter to true.

The actual xrandr command may of course look different, depending on the actual number and layout of screens. So YMMV!

The kioslave fish:/ enables you to access remote files through ssh, even if sftp is not installed on the remote host. It’s much more convenient than its cousin sftp:/, e.g. because dolphin remembers file associations etc.

Unfortunately, fish:/ requires perl. It copies a perl script to the remote host and execute it there. So if you run into an error like

Could not enter folder fish://root@HOST/root

when you try to point konqueror or dolphin to fish://root@HOST, the culprit could simply be a missing perl package on the remote host. Installing perl-URI should suffice:

# yum install perl-URI

For further debugging of the fish:/ kioslave, have a look at http://techbase.kde.org/Development/Tutorials/Debugging/Debugging_IOSlaves/Debugging_kio_fish

If Netbeans’ keyboard shortcut for fixing import statements (or any other shortcut) stops working, it could be the KDE global shortcuts daemon interfering¹². Per default, Ctrl+Shift+I is bound to Kopete’s read message function, so if Kopete runs in background, Netbeans doesn’t catch the shortcut. Quick Fix: Close Kopete or simply remove the global shortcut.

To check, if the kdedglobalaccel daemon uses Ctrl+Shift+I, simply use

$ grep -i ctrl+shift+i ~/.kde/share/config/kglobalshortcutsrc
ReadMessage=Ctrl+Shift+I,Ctrl+Shift+I,Read Message

You can either just remove the line from ~/.kde/share/config/kglobalshortcutsrc, use KDE’s System Settings tool (System Settings → Shortcuts and Gestures → Global Keyboard Shortcuts → KDE component: Kopete → Read Message)

System Settings: Change "Read Message" to "None" (click for full size image)

or unset the shortcut in Kopete itself (Kopete → Settings → Configure Shortcuts → Read Message)

Kopete: Change "Read Message" to "None" (click for full size image)

[1] http://netbeans.org/bugzilla/show_bug.cgi?id=117058
[2] http://netbeans.org/bugzilla/show_bug.cgi?id=187776

Especially on large pdf files, okular tends to occupy insane amounts of memory. That’s because already rendered pages are kept in the cache for faster revisit and as you scroll quickly through a large pdf (let’s assume a couple hundred pages), okular can easily occopy Gigabytes of RAM for a few MB sized pdf file.

The problem is existing for quite a while and a couple of version now and there is even a bug report in the kde bug tracker. As a quick fix, I would simply suggest to lower okular’s MemoryLevel. Modern processors usually render regular pages (eBooks, datasheets, application notes etc.) almost instantly and as long as you don’t mess around with technical drawings or other render-intensive stuff inside the pdf, there is really no reason to use heap space that aggressively.

You can either use the GUI (Settings → Configure Okular… → Performance → Memory Usage) to the the Memory Usage to “Low”,

Change "Memory Usage" to "Low" to prevent caching (click for full size image)

or change the MemoryLevel variable in .kde/share/config/okularpartrc to “Low”. If the variable (or the “Dlg Performance“-Section) doesn’t exist, simply create it.

[Dlg Performance]
MemoryLevel=Low

Quite a few applications use ~/.local/share/recently-used.xbel to keep track of a user’s most recent files. Unfortunately, not every application offers customization options to disable this list.

One possible solution, granted, a quite hacky one, is to clear recently-used.xbel and revoke a user’s permission to edit it again.

First, remove and re-create the file to clear it

$ rm -f ~/.local/share/recently-used.xbel 
$ touch ~/.local/share/recently-used.xbel 

You can then edit the permission so that the user can’t edit the file any more.

$ chmod -w ~/.local/share/recently-used.xbel 

For KDE, there is quite a similar mechanism. While there is no single file that stores the recently used items, a .desktop file is created in ~/.kde/share/apps/RecentDocuments/ for every item.

If if you revoke a user’s writing permission to that folder, KDE won’t add any item to the ‘recently used’ list.

$ chmod -w ~/.kde/share/apps/RecentDocuments/