Multi-line commands about 21sh HOT 1 CLOSED

21sh currently moves left/right with the termcaps commands le and nd. We can similarly move up/down with the commands up and do.

Using these commands will lead to unwanted behavior in several different scenarios:

• Moving left past the beginning of a line
  -- we can guard against this by checking if the line index would be negative before moving
• Moving right past the end of a line
  -- guard against this by checking if the next index would be past the size of the line, or the next newline
• Moving up past the first line of a command
  -- we can guard against this by checking the current index has a newline preceding it
• Moving down past the last line of a command
  -- we can guard against this by checking the current index has a newline following it
• Moving up when next line ends before current column
  -- we can guard against this by finding the current relative index (current column on screen), and moving left until we're on the first column. then move up one row, and move right until we encounter the next newline or reach the current relative index
  --If we're on the first line, need to consider the space the prompt occupies (if no preceding newline, move up then left for size of prompt before calculating indexes)
• Moving down when next line ends before current column
  -- we can guard against this by finding the current relative index (current column on screen), and moving left until we're on the first column. then move down one row, and move right until we encounter the next newline or reach the current relative index

from 21sh.