Currently only ASCII DEL (key code 127) is handled as backspace, but some terminal
emulators are sending ^H which is ASCII BS (key code 8). Looks like we can
safely treat both in the same matter.
The current code for entering commands via the serial CLI is completely
refactored and moved out of rtlplayground.c into a separate file cmd_edit.c
putting code into BANK2.
The serial ring buffer sbuf[] is now exclusively used for receiving
keys, including escape sequences (DEL will generate a 4-byte escape
sequence). The command is now held in cmd_buffer. This reduces
XMEM use, because the serial buffer can be much smaller.
Supported is only editing the current command line via backspace, del,
cursor left and right.
Because the code cannot distinguish escape sequences which are not yet
complete (because the serial isr has not yet put all characters into
the serial buffer) from the dozens of unsupported ones (F-keys/home,
Page up/down, cursor up/down...) they are ignored and remain in the
serial buffer until the ring-pointer overwrites them. This is standard
behaviour for consoles, which will print out garbage for unsupported
characters. In this implementation, the command line buffer and the
visible command line in the terminal are always synced, so garbage
can be removed again by ediing the line.
The code makes several redundant checks in order to prevent race-conditions
between the serial ISR and the comand-editing code.
diijkstra
logicog