[MJ] - I have just discovered [bindtags] and what they can do. They allow for some really advanced keyboard handling. An example of this is the base for a Tcl editor below. Keybindings can be associated to certain modes (a la [Emacs]) This is just a rudimentary basis, but I will expand on this when I have time.

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 package require Tk
 
 namespace eval buffer {
     proc get-point {buffer} {
 	return [$buffer index insert]
     }
 
     proc get-line-with-point {buffer} {
 	set point [get-point $buffer]
 	set line [$buffer get "$point linestart" "$point lineend"]
 	return $line
     }
 
     # return a list with all bindings on buffer (global and buffer)
     proc list-bindings {buffer} {
 	set bindings {} 
 	foreach tag [bindtags $buffer] {
 	    set bindings [concat $bindings [bind $tag]]
 	}
 	return $bindings
     }
 
     proc create_new {} {
 	text .t
 	pack .t -expand 1 -fill both
 
 	# default bindtags for any new buffer
 	bindtags .t "fundamental-mode keymap [bindtags .t]"
 	return .t
     }
 
     proc major-mode {buffer mode} {
 	bindtags ${buffer} "$mode [lrange [bindtags ${buffer}] 1 end]"
         # call mode-hook here
 	wm title . $mode
     }
 }
 
 namespace eval kb {
     # Stuff to detect key modifiers (taken from http://wiki.tcl.tk)
 
     # array of bit masks to recognize the modifers:
     # - shift - mod5 masks taken from .../tcl/include/X11/X.h
     # - alt mask defined by analysing the status field of Alt-KeyPress
     #   (analysed on MS Windows)
     #
     array set masks [list \
 			 shift   [list [expr {1 <<  0}] "Shift"] \
 			 lock    [list [expr {1 <<  1}] "Lock"] \
 			 control [list [expr {1 <<  2}] "Control"] \
 			 mod1    [list [expr {1 <<  3}] "Mod1"] \
 			 mod2    [list [expr {1 <<  4}] "Mod2"] \
 			 mod3    [list [expr {1 <<  5}] "Mod3"] \
 			 mod4    [list [expr {1 <<  6}] "Mod4"] \
 			 mod5    [list [expr {1 <<  7}] "Mod5"] \
 			 alt     [list [expr {1 << 17}] "Alt"] \
 			];
     
     # MS Windows modifier name map:
     # - Mod1 is identical to "Num"-lock key
     # - Mod3 is identical to "Scroll"-lock key
     #
     set maps [list \
 		  "Mod1" "Num" \
 		  "Mod3" "Scroll" \
 		 ];
     
     proc keyModifiers {state {mapToRealName 1}} {
 	variable masks;
 	variable maps;
 	
 	set modifiers [list];
 	
 	foreach mask [array names masks] {
 	    lassign $masks($mask) bits label;
 	    
 	    if {$state & $bits} {
 		lappend modifiers $label;
 	    }
 	}
 	
 	set modifiers [join $modifiers "-"];
 	
 	if {$mapToRealName == 1} {
 	    set modifiers [string map $maps $modifiers];
 	}
 	
 	return $modifiers;
     }
     
     proc add-binding {tag key proc} {
 	set keys [split $key]
 	if {[llength $keys] == 1 } {
 	    # simple keys
 	    bind $tag ${key} $proc
 	} else {
 	    # create binding for the prefix
 	    bind $tag "<[lindex $keys 0]>" {event generate .mini <<HandlePrefix>> -data [list %W %s %K]}
 	    
 	    # create binding event for the whole shebang
 	    bind $tag "<<${key}>>" $proc
 	}
     }
 
     # minibuffer will handle prefixed commands 
     proc handle-prefix-binding {buffer state key} {
 	# here the system can collect keybindings until a binding matches
 	set prefix "[keyModifiers $state]-$key"
 	set all_bindings [::buffer::list-bindings $buffer]
 	
 	# add enable minibuffer bindtag
 	focus .mini 
 	set ::*mini-buffer* {}
 	set ::*mini-buffer* "$prefix "
     }
 }
 
 # scratch mode bindings
 ::kb::add-binding scratch-mode <a> {puts "in scratch mode"; break}
 ::kb::add-binding scratch-mode <Control-j> {puts "should execute [::buffer::get-line-with-point %W]"; break }
 ::kb::add-binding scratch-mode <Control-J> {puts "should execute something now without displaying output" ; break }
 
 ::kb::add-binding scratch-mode "Control-x Control-b" {puts prefixed}
 ::kb::add-binding scratch-mode "Control-x Control-c" {puts prefixed}
 
 # global keybindings
 ::kb::add-binding keymap <Control-space> {puts [::buffer::get-point %W]}
 
 set buff [::buffer::create_new]
 

 # rudimentary minibuffer. The current state of the minibuffer will be determined by the active bindtags
 entry .mini
 pack .mini -expand 1 -fill x
 
 .mini configure -textvar *mini-buffer*
 
 # prefix commands trigger a <<HandlePrefix>> event on the minibuffer with arguments
 # <originating widget> <keystate> <key>
 
 # also enable minibuffer chording bindtag  
 bind .mini <<HandlePrefix>> {set *mini-buffer* %d ; focus .mini ;  break}
 
 # also disable minibuffer chording bindtag on Control-g
 bind .mini <Control-g> {focus [lindex [set *mini-buffer*] 0] ; set *mini-buffer* "Aborted" ; break }
 bind .mini <KeyPress> {set *mini-buffer* [list {expand}[set *mini-buffer*] %s %K]}
 .mini configure -state disabled
 
 ::buffer::major-mode $buff scratch-mode
 
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[Category Word and Text Processing]