Example - Emulating Compose key using chained dead keys

Installer package: KbdEditInstallerUSWithLinuxComposeKey.exe

Layout file: US With Linux Compose Key.zip

Dead key table file: LinuxComposeKeys.zip

You can use the installer package to deploy this keyboard layout without any restrictions. Free Demo version can be used to make changes and test them. To deploy a modified version, a Premium, Personal or Lite edition is needed.

Keyboards on most Unix-based systems support a special Compose key, which offers an intuitive way to enter accented and other special characters as mnemonic sequences of 2 or 3 standard characters. For example, sequence <Compose> A E produces letter ƒj , <Compose> 1 4 produces fraction ƒV , <Compose> ^ T M produces trademark symbol ? etc (the complete list is shown further below).

This method proves very intuitive and easy to learn. Even though 3 or 4 key presses are needed to produce a special character, the composition characters tend to resemble the visual appearance of the final character, which makes them easy to memorize.

Windows does not support an equivalent of Compose key out of the box, but this function is very easy to emulate using chained dead keys. This example shows one such layout, in which Compose is mapped to the rarely used Scroll Lock key.

If you primarily use the standard US English keyboard, you can use the US With Linux Compose Key.zip layout without any changes (the examples page explains how).

If you use a different layout, you will have to add the Compose dead key table to it and map the Compose dead key:

• First, you have to switch to the Dead char editor and use the Import dead char table from KLD file command to import the attached LinuxComposeKeys.zip .
• To make the Scroll Lock key available for the compose function, you should first use the low-level editor to assign a "mappable" virtual key code (eg VK_ATTN) to the "physical" Scroll Lock key (scan code 0x46), as explained in this example.
• After that, the high-level view is used to assign the 0043 C _Compose dead key to both Base and Shift positions of the VK_ATTN virtual key.

Note that Compose is the only dead character that needs to be mapped to a key in the high-level view. All other interim and final dead characters (55 of them) are produced by chaining. Furthermore, only Compose is represented by a "printable" character (C). The remaining 55 dead characters are assigned to successive numerical values (E000 - E036) from the "Private Use" area. This ensures that the "compose" dead table doesn't interfere with any pre-existing dead keys.

The above demonstrates one important feature of chained dead keys: they use high-level mappings very frugally, leaving most of the positions free for standard mappings. It is not even necessary to reserve an entire key for the Compose function: instead of Scroll Lock, Compose can also be mapped to any unused modifier + VK position in the high-level editor, e.g. AltGr+C.

Compose dead table mechanics

If you decide to further customize the composition table, you'll need to know how the Compose key works behind the scenes.

As an example, we'll use the trademark symbol ? whose composing sequence is Compose ^ T M .

Complete composition table

The below table shows all composition sequences supported by this example (table taken from here).

The table is not exhaustive but the dead char editor, together with information from this example, is all you need to add composition sequences for missing special characters. (Eg certain Unix systems support Greek accented letters, and/or additional sequences for the existing special characters).

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