Casandro/viewdata_decoder

A rudimentary Viewdata decoder that can be adapted to various needs.

How to use as a user:

cd decoder
make
./viewdata_ncurses nx.nxtel.org 23280

How to use to write your own terminal emulator:

See viewdata_ncurses.c as a basic example.

• Use viewdata_init_and_connect(hostname, port) to initialize the viewdata screen and connect to a host.
• Write an input loop that checks for characters from our input device and calls viewdata_handle_stuff() with the characters you want to send.
  • Minimal useful input is digits 0-9 (0x30-0x39) and both ⚹ (0x2A) and ⌗ (0x5F, different from US-ASCII).
  • 0-9 indicate options. ⚹ starts an absolute page number. ⌗ ends the absolute page number or goes to the next page.
  • Exact shapes for this can be found in ITU-T E.161 figure 2 and 3.
  • Keypad input should be aranged like this: (If simulating the keypad with a d-pad, it might make sense to use a "cursor" on it, and to either return to # or have a separate button for it.)

	1 2 3
	4 5 6
	7 8 9
	⚹ 0 ⌗

• Call viewdata_handle_stuff() periodically with -1 to process data that comes from the network.
• If viewdata_handle_stuff() returns with a non-zero value, update your screen.
  • Rows can be considered to be individual objects.
  • To get decoded character cells of a row, each containing the attributes of that cell use viewdata_convert_row(row, cells);
  • To fill a bitplane bitmap use viewdata_240_update_row. Data for one text row (10 pixel lines) will be available in a vd_240_line_t object.
  • The image data is stored in 3 member arrays: red, green and blue. The element type is uint8_t;
  • Each bit represents a pixel. 0 is dark and 1 is lit.
  • Most significant bit is left.