Ok, grappling with this xmodmap issue has caused me to revisit the issue of inputting non-latin characters under Linux, something I dealt with a few years ago. Finally, with helpful hints gotten in on-line forums and reading various README files, I had some success. I observe now that I displayed a bit of prescience back then as well.
For posterity's sake, I'm pasting here the resolution I came up with--the prescient bit (written almost 8 years ago) highlighted in bold:
. . . I'm taking the other approach I mentioned earlier (editing XF86Config-4 to allow for keyboard map/font switching for X apps). He's also helped me out with this. . . . there is an additional line possible in the keyboard stanza of XF86Config-4 (this refers to 4.3.0something and may not apply to earlier releases): the XkbVariant" line. In order to get the phonetic Russian and polytonic layouts (or at least a semblance of polytonic) I want, I've added the "XkbVariant" line with ",phonetic,polytonic" following. That has gotten me most of the way to where I need to be in entering unicode input into Xapps. It also works in a console if you have the right fonts installed. As an additional detail, I should mention that I think you must have a unicode locale specified in your system for this to work. In my case, I've set locale to en_US.UTF-8 (how to set that varies by distribution: dpkg-reconfigure locales is how Debian does it). I'll provide the relevant section of my XF86Config-4 for those interested:Now, as those of you who've been working with GNU/Linux this long will know, we no longer edit GUI configuration files by hand: these are to be auto-generated by the system. But sometimes, for whatever crazy reason, you'll need to do some tricky thing like I was doing then so that you can switch keyboard layouts on the fly.
Identifier "Generic Keyboard"
Option "XkbRules" "xfree86"
Option "XkbModel" "pc104"
Option "XkbLayout" "us,ru,el"
Option "XkbVariant" ",phonetic,polytonic"
Option "XKbOptions" "grp:alt_shift_toggle,grp_led:scroll"
Note the "grp_led:scroll" segment too, which causes the scroll lock LED on the keyboard to light up when I'm in one of the alternate keyboard/font mappings. In summary, I've written this in the hope it may help someone else wanting to do this under Linux. . . . my little research/how to project here could likely be itself obsoleted pretty shortly.
In current circumstances, for example, my work computer uses a very minimalist desktop that includes no keyboard-layout switching utility/applet--something Gnome, KDE, XFCE4, and the like, do include. So, if I want to implement keyboard-layout switching there, I'm going to need a solution like the one I implemented several years ago.
I suppose it's still possible to hand-edit the GUI configuration file--now called xorg.conf, as we may all know--but that, I believe, is not the canonical method. Instead, what's now expected is that modifications such as the one above be entered into a different configuration file, from whence they get loaded into the xorg.conf file the system automatically generates.
That file is located (on Debian-based systems) in /etc/default and is called, appropriately enough, "keyboard." The content needed to implement the modifications listed above--along with further context from that file--will look as follows:
# If you change any of the following variables and X is configured to
# use this file, then the changes will become visible to X only if udev
# is restarted. You may need to reboot the system.
# The following variables describe your keyboard and can have the same
# values as the XkbModel, XkbLayout, XkbVariant and XkbOptions options
# in /etc/X11/xorg.conf.
# If you don't want to use the XKB layout on the console, you can
# specify an alternative keymap. Make sure it will be accessible
# before /usr is mounted.
There's my demonstration of prescience for the year (I hope that doesn't change again within the year). Now, on to a revisitation of the xmodmap issue.
More on xmodmap
Turns out the xmodmap issue is in no way unique to XFCE4: rather, it seems to affect many, and perhaps all, graphical environments. As a moderator from the Arch Linux forums put it almost exactly two years ago, "This is an unsolved problem for quite some time" (see this thread for a bit of further detail).
The symptom on the machine I'm trying this with is that it xmodmap will not initiate when the GUI comes up, despite my attempts at placing commands intended to invoke it in relevant start-up files: xmodmap will only take effect when run manually after the graphical environment is running. Even then, it causes 100% CPU usage for several seconds while it is initiating (this is a pretty low-resource system, at only 800 Mhz, which partly explains the delay).
What is the nature of this problem? Why can't this re-mapping or re-binding be done in connection with the user's log-in and graphical environment's initiation? Does it have something to do with evdev which, as I understand it, is what implements the system's auto-configuration of peripherals like keyboard and mouse? I simply do not understand, unfortunately.
But this matter seems to have foiled greater minds than my own. As a case in point, while trying to resolve this and similar problems, I bumped into the following example in the Xsession man page--which even seemed calculated to address specifically the problem I was trying to resolve:
Here is an example of how one might write a script, named 40custom_load-xmodmap, to invoke xmodmap(1): SYSMODMAP="/etc/X11/Xmodmap" USRMODMAP="$HOME/.Xmodmap" if [ -x /usr/bin/X11/xmodmap ]; then if [ -f "$SYSMODMAP" ]; then xmodmap "$SYSMODMAP" fi fi if [ -x /usr/bin/X11/xmodmap ]; then if [ -f "$USRMODMAP" ]; then xmodmap "$USRMODMAP" fi fi
Well, I tried that. I created a file with that content, put it in the recommended directory (/etc/X11/Xsession.d) and gave it the same permissions as the other files in that directory. But the xmodmap modifications I'd stipulated were not in effect once the graphical environment came up: I still had to run xmodmap manually.
The only thing approaching a resolution I've found that's calimed to work, is a really ugly looking hack I read about on the Archbang forums (you can read about it here). I haven't tried it yet and so cannot confirm that it works: and I hope to avoid trying it. I really hope there's something a bit less kludgy that'll resolve the issue.
As for things I might attempt, I've thought of entering each of my eight modifications on separate lines in the .xsession or .xinitrc file to see whether that'll cause the modifications to take effect when the user logs in--though that solution isn't much prettier than the one outlined on the Archbang forum. If I did do that, I assume the lines would take the form xmodmap -e “keycode 12 = 3 numbersign 3 numerosign” &. If I try that and it's any more successful, I'll report back about it.
Meantime, I'm still looking for more informed helpers with this issue. Got any insights?