Here's the outline of how this design is arrived.
Statistics of emacs commands are compiled from emacs users, and are listed by frequency of use. The top about 30 ones, are given a keyboard shortcut.
To assign the key position, the following rules are used. The rules are listed roughly in order of priority:
- Home row keys are the best.
- 2nd and 3rd fingers (pointing finger and index finger) are better than 4th (ring finger) and 5th finger (pinky).
- The row above home row is considered better than the row below home row for 2nd and 3rd fingers. (for 5th finger the row below is considered better.)
- Right hand's keys are considered better than left hand's keys. (because most people are right handed)
- Alt is considered better than Ctrl. (Alt is a natural thumb curl, Ctrl is stretched pinky. Thumb is most powerful finger, pinkie the weakest)
- In general, cursor moving commands are placed all for the right hand, while text changing commands are all placed for the left hand. (grouping advantage)
- Similar commands should be grouped together to avoid scattering. For example, cursor moving by single char is together (I J K L). Undo, Cut, Copy, Paste are together (Z X C V). Delete char/word left/right are together (E R D F).
- Commands with logical reversal or extension are done with ⇧ Shift key, after other priorities are considered. Examples: Undo/Redo, move cursor to previous/next pane, find replace by string/regex, isearch forward/backward, move cursor by beginning/ending of line. Delete line to the right/left.
The design is based on finger positions, not on first letter of command names. The shortcut set is the same for QWERTY and Dvorak. The ease of remembering what commands are on what keys are based on grouping and positioning. For example, cursor movings are all right hand, text changing are all left hand, moving or deleting to the left/right have keys that are place left and right together, and similar for up/down (by screen or to beginning/end of file). Undo, Cut, Copy, Paste are the familiar row Z X C V.
In this design, only the Alt+‹key› space is used. Some Alt+⇧ Shift is used too. Ctrl+‹key› space is not used except 7 standard keybindings (Open, Close, Save, Save As, Print, Select All). The operation and consistency of emacs is not affected.