How to pass Combining characters for custom keyboard layout in Ubuntu?

Question

I was creating my custom keyboard layout(custom tamil keyboard layout) in Ubuntu 12.04 platform based on this post. I edited the file /usr/share/X11/xkb/symbols/in as specified in the post with my custom layout. The sample layout mapping is attached below:

partial alphanumeric_keys
xkb_symbols "tam_font_test" {
// Description: Tamil Custom Font KeyMap
// Encoding: Unicode (http://www.unicode.org)
// Author: Test

name[Group1]= "Tamil (Font Map - Test)";

// Qrow
key <AD02> {  [ U0BB1 ] };
key <AD03> {  [ U0BA8 ] };
key <AD04> {  [ U0B9A ] };
key <AD05> {  [ U0BB5 ] };
key <AD06> {  [ U0BB2 ] };
key <AD07> {  [ U0BB0 ] };
key <AD08> {  [ U0BC8 ] };
key <AD10> {  [ U0BBF ] };
};

I was successful with the above layout mapping.

However I have a typical requirement which i wasnt able to do it. I would like to map the key AD03 with the following map

key <AD03> {  [ U0BA8, U0BA8+U0B8A ] };

where the second argument is the combining character such as this.
The syntax for the definition can be found in this link.
The unicode character for tamil character can be found here.

How can we pass the combining characters unicode as an argument to the mapping?

Answer 1

Not really an answer but a quote:

The line key { [ quoteleft, asciitilde ] }; describes a single mapping from a key code ( in this case) to a group of symbols (` and in this case). Symbols are named, using the symbolic names from the /usr/X11R6/include/X11/keysymdef.h file, as described in section 2.4. A pair of symbols enclosed in brackets indicates a pair of symbols separated by a shift level; pressing the Shift key usually shifts between two levels, but the types component can override this. If a single symbol is enclosed in brackets, then this symbol is used always, independent of the level.

maybe a link is of some use: http://www.charvolant.org/~doug/xkb/html/node5.html