Factors in keyboard layout creation

When developing keyboards for a particular market, a number of factors should be taken into consideration:

• Is there some kind of keyboard standard for the region or country? It is sometimes required to have an input method which is sanctioned by the government or an appropriate governing body. Implementers should consider contacting their local or national standards body prior to developing a keyboard. In addition, implementers should consider de facto standards (that is, standards which are not official, but are used by so many people that they are considered 'standard').
• What languages will the keyboard support? This should be explicitly determined before allocating keys to characters
• Does the keyboard provide input of all needed linguistic characters for the appropriate language(s)? This requirement can be met in a number of ways: via dead keys or additional shift states, for example (not all characters need to be on the unshifted state). High frequency linguistic characters should be positioned where they are easy to type, ideally in the unshifted state. (Note that if the keyboard supports multiple languages, the high frequency keys may change)
• Does the keyboard focus on code points, and not glyphs? It is important to not place the burden of display or shaping onto the keyboard. All technologies related to visual display are decoupled from the keyboard (and should be handled by fonts and a rendering engine if needed; see section 4 for more information).
• Do all characters on the keyboard exist in Unicode? Since all input on Windows is based on Unicode (UTF-16), any code points not encoded in Unicode cannot be handled.
• Are supplementary characters (non-BMP characters) encoded in UTF-16 and handled in the ligature section of the keyboard? Is the limit of 2 supplementary characters (4 UTF-16 code points) met on each key?
• Ideally, a keyboard should be consistent in its behavior concerning precomposed Vs.composite characters.