puter/packages/phoenix/doc/graveyard/keyboard_modifiers.md

keyboard modifier translation

Encoding of modifier keys in xterm is done following this table:

encoded	keys pressed
2	Shift
3	Alt
4	Shift + Alt
5	Control
6	Shift + Control
7	Alt + Control
8	Shift + Alt + Control
9	Meta
10	Meta + Shift
11	Meta + Alt
12	Meta + Alt + Shift
13	Meta + Ctrl
14	Meta + Ctrl + Shift
15	Meta + Ctrl + Alt
16	Meta + Ctrl + Alt + Shift

This script was used to convert between more useful bit flags and the xterm encodings of the modifiers:

const modifier_keys = ['shift', 'ctrl', 'alt', 'meta'];
const MODIFIER = {};
for ( let i=0 ; i < modifier_keys.length ; i++ ) {
    MODIFIER[modifier_keys[i].toUpperCase()] = 1 << i;
}

const pc_modifier_list = [
    MODIFIER.SHIFT,
    MODIFIER.ALT,
    MODIFIER.CTRL,
    MODIFIER.META
];

const PC_STYLE_MODIFIER_MAP = {};

(() => {
    let i = 2;
    for ( const mod of pc_modifier_list ) {
        const new_entries = { [i++]: mod };
        for ( const key in PC_STYLE_MODIFIER_MAP ) {
            new_entries[i++] = mod | PC_STYLE_MODIFIER_MAP[key];
        }
        for ( const key in new_entries ) {
            PC_STYLE_MODIFIER_MAP[key] = new_entries[key];
        }
    }
})();

for ( const k in PC_STYLE_MODIFIER_MAP ) {
    console.log(`${k} :: ${print(PC_STYLE_MODIFIER_MAP[k])}`);
}

However, it was eventually determined that the PC-style function keys, although this is not documented, really do represent bit flags if you simply subtract 1.

For example, this situation doesn't look like it can be explained using bit flags:

• shift is 2
• ctrl is 5, and has two 1 bits
• shift + ctrl is 6
• flags don't explain this: 2 | 5 = 7

But after subtracting 1 from each value:

• shift is 1
• ctrl is 4
• shift + ctrl is 5
• flags work correctly: 1 | 4 = 5

This is true for all examples.