A number of contributors to the Wiki have expressed some interest in working with matters 'Chinese'. So, here's my contrition. I'm currently working on a project to create language learning flashcards in Tcl, and of course, pinyin is vital to enable learners to get a handle on the characters that they are reading. It also helps too, if there is some confusion over the tones pronounced. (Snack does a brilliant job of recording and playing back the sound phrases). Well, enough rambling, here's the code I came up with. By the way, it's designed to run on a Windoze box. Some feedback from Mac/Linux users would be useful.

 # -------------------------------------------------------------
 # pinyin_input.tcl
 # Written by William J Giddings, May, 2005.
 # -------------------------------------------------------------
 # Usage:
 # pinyin_input <widget>
 # 
 # Purpose:
 # --------
 # Assigns necessary bindings to a widget in order to
 # interpret multiple key-presses as tone inflected vowels.
 #
 # User operation:
 # ---------------
 # 
 # Alt-vowel-Alt-tone
 # Alt-<a|e|i|o|u|y>-Alt-<1|2|3|4>
 # 
 # The fifth or neutral tone takes no diacritic, so is entered as
 # an unmodified key.
 # 
 # In the case of the umlauted u:, enter the vowel as 'y'
 #
 # Notes: 
 # ------
 # Use versions of ttf 2.76 or higher. These include the necessary 
 # diacritics to display all pinyin vowels plus their tone marks.
 #
 # ------------------------------------------------------------- 
 
 # -------------------------------------------------------------
 # modify widget bindings to insert pinyin vowels
 # -------------------------------------------------------------
 proc {pinyin_input} {txt} {
    proc {_pinyin_insert} {w v t} {
 	switch $v$t {
		a1 { set code 0101 }
			a2 { set code 00E1 }
			a3 { set code 01CE }
			a4 { set code 00E0 }
			A1 { set code 0100 }
			A2 { set code 00C1 }
			A3 { set code 01CD }
			A4 { set code 00C0 }
			e1 { set code 0113 }
			e2 { set code 00E9 }
			e3 { set code 011B }
			e4 { set code 00E8 }
			E1 { set code 0112 }
			E2 { set code 00C9 }
			E3 { set code 011A }
			E4 { set code 00C8 }
			i1 { set code 012B }
			i2 { set code 00ED }
			i3 { set code 01D0 }
			i4 { set code 00EC }
			I1 { set code 012A }
			I2 { set code 00CD }
			I3 { set code 01CF }
			I4 { set code 00CC }
			o1 { set code 014D }
			o2 { set code 00F3 }
			o3 { set code 01D2 }
			o4 { set code 00F2 }
			O1 { set code 014C }
			O2 { set code 00D3 }
			O3 { set code 01D1 }
			O4 { set code 00D2 }
			u1 { set code 016B }
			u2 { set code 00FA }
			u3 { set code 01D4 }
			u4 { set code 00F9 }
			U1 { set code 016A }
			U2 { set code 00DA }
			U3 { set code 01D3 }
			U4 { set code 00D9 }
            # u:1 - u:4
			y1 { set code 01D6} 
			y2 { set code 01D8} 
			y3 { set code 01DA} 
			y4 { set code 01DC}
            # U:1 - U:4
			Y1 { set code 01D5}
			Y2 { set code 01D7}
			Y3 { set code 01D9}
			Y4 { set code 01DB}	
			}
		#puts $code 
		$w insert insert [subst \\u$code] 
	}
    # create specific bindings
	foreach {vowel} {a A e E i I o O u U y Y} {
			bind $txt <Alt-Key-$vowel><Alt-Key> [list _pinyin_insert %W $vowel %K]
		} 
 }
 # -------------------------------------------------------------
 # test the code
 # -------------------------------------------------------------
 proc demo  {} {
    package require Tk
    text .txt -font {Ariel 14}
    pack .txt -fill both -expand 1 
    pinyin_input .txt
 }
 demo