Support various common navigation commands in the editor #32

Navigate to:

• Start of word/line/document: Ctrl ←, HOME, Ctrl HOME
• End of word/line/document: Ctrl →, END, Ctrl END
• Previous cursor location: Ctrl -
  • (requires some kind of cursor location history stack)
• Next cursor location: Ctrl Shift -
  • (requires some kind of cursor location history stack)
• line:column: Ctrl: L

Select:

• From cursor until start of word/line/document: Same as the navigate shortcuts, with the Shift modifier
• From cursor until end of word/line/document: Same as the navigate shortcuts, with the Shift modifier

Research

Turns out this is actually quite difficult.

TTY

After reading a brief history of TTY it becomes apparent that terminal applications (including TUI applications) have quite a few constraints as a result of historical baggage.

For example:

$ stty -a
speed 38400 baud; rows 73; columns 238; line = 0;
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>; eol2 = <undef>; swtch = <undef>; start = ^Q;

The second line of stty -a output lists all the special characters.

So depending on which characters are reserved by the TTY config, various characters may simply be unavailable for use.

OS Shortcut Keys

The OS can also capture various keys. By default, macOS swallows Ctrl + ← and Ctrl + → as these are mapped to Mission Control shortcuts.

This makes it very difficult to map common shortcuts used in modern OSX or Windows applications to do what people familiar with those OS conventions might expect in a TUI application...