patacongo edited a comment on pull request #1851:
URL: https://github.com/apache/incubator-nuttx/pull/1851#issuecomment-695799871
The following is nonsensical:
> Note that that thread could like in your featherwing driver logic. There
is a function in nxterm_driver.c called nxterm_ioctl_tap() that permits the
nxterm ioctl commands to be called from within the OS. You might even be able
to come up with a solution that does not require a dedicated "listener" thread.
Perhaps keyboard input could be handled on the work queue and
nxterm_ioctl_tap() could be called directly. This makes sense because the
featherwing is really an integrated solution, is it not?
That is a really dumb idea, of course. The correct behavior is rather
complex. Let me try:
**The Normal Case:**
Keyboard and mouse inputs are received by the application through window
callbacks, just like with the X server. The listener needs to inject the
keyboard input via nx_kbdin (libs/libnx/nx_kbdin.c) which sends a message to
the NX server. The NX server will forward the keyboard input to the window
that has focus.
The Window application listens for NX server events by calling
nx_eventhandler() (libs/libnx/nx_eventhandler) which, if the window has focus
when the keypress is entered, forwards the keypress info to the registered
window even handler.
In apps/examples/nxterm, nxterm_listener.c is the thread that drivers
nx_eventhandler(). The "normal" window NX keyboard callback is the function
nxwndo_kbdin() in nxterm_wndo.c. It just writes the keyboard data to stdout.
**The apps/examples/nxterm/kludge:**
apps/examples/nxterm does not do things in the normal way. NSH does not
receive keyboard input from NX; it gets it directly from stdin which is
probably the host PC serial console. This is okay because only the background
window is used and that example does not need the help of NX.
**Re-direction of stdout and stderr:**
Stdin in and stderrwere re-directed to the NxTerm in nxterm_main.c:
399 /* Now re-direct stdout and stderr so that they use the NX console
driver.
400 * Note that stdin is retained (file descriptor 0, probably the
serial
401 * console).
402 */
403
404 printf("nxterm_main: Starting the console task\n");
405 fflush(stdout);
406
407 fflush(stdout);
408 fflush(stderr);
409
410 fclose(stdout);
411 fclose(stderr);
412
413 dup2(fd, 1);
414 dup2(fd, 2);
The BOARDIOC_NXTERM_IOCTL is only called for the case of a redraw event.
This happens when a window "above" the current window is moved and the text is
exposed.
If you use only the background window, then it will always have focus. It
will always have focus and will never be redrawn and the BOARDIOC_NXTERM_IOCTL
will never be used. Unless, perhaps, you choose to implement pop-up error
messages or menus on top of the NxTerm.
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