Re: Bugs when porting ncurses to a new platform

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On Tue, Jun 30, 2026 at 12:27:45AM +0000, Antonio Ni=F1o D=EDaz wrote:
> Hello!
>=20
> I'm trying to get ncurses working in a new platform (Nintendo DS using
> [BlocksDS](https://blocksds.skylyrac.net/)).  I've created a terminal
> emulator that supports 16-color, 256-color and direct color commands
> (foreground and background), as well as a few other commands like "bold",
> "move cursor" and "clear screen".  Basically, I'm cherry-picking terminfo
> configuration settings from other terminals to create my own configuration
> based on what I actually support, and I'm trying to understand every sett=
ing
> I use.  So far I've managed to get 16 and 256 color modes working, as wel=
l as
> moving the cursor around and clearing the screen.  However, I have two is=
sues
> that I've spent a few days debugging with no success.  I've even added pr=
intf
> logs in ncurses in many places (the trace system doesn't work for some
> reason) but ncurses has so many build options and code paths that it's ha=
rd
> to know what actually gets used (printf-debugging has helped to get color
> working, though).
>=20
> ----------------
=2E..
> 2) getch() only works for blocking input.
>=20
> If I use `timeout(-1)` I can see calls to `read()`.  They block as expect=
ed
> and I can see that the value is received by ncurses.  However, if I use
> `timeout(0)` I never see any syscall being used.  Maybe I'm looking at the
> wrong place, but the same code works on PC, so I assume it's something to=
 do
> with my port.  I do support setting non-blocking mode for `stdin` with
> `ioctl(FIONBIO)` and `fcntl(F_SETFL, O_NONBLOCK)`, and I also support
> querying the amount of characters available to read from `stdin` with
> `ioctl(FIONREAD)`, but I don't know if this is even used by ncurses.

no - ncurses basically uses select() or poll() to detect new data.

In a quick check, timeout() sets a _delay member of the window,
which when negative will bypass a timed delay when looking for data.
=20
> How does ncurses get new characters for non-blocking input?
>=20
> ----------------
>=20
> This is my build configuration:
>=20
> ./configure \
> --with-normal \
> --without-shared --without-progs --without-manpages --without-tests \
> --target=3Darm --host=3Darm --build=3Damd64 \
> --disable-database --disable-db-install \
> --disable-gnat-projects --disable-home-terminfo \
> --enable-termcap \
> --disable-widec \
> --prefix=3D$PWD/mybuild \
> --with-trace \
> --enable-getcap \
> --disable-sigwinch \
> --enable-ext-colors --enable-rgb-color \
> --enable-ext-mouse \
> CFLAGS=3D"-mthumb -mcpu=3Darm946e-s+nofp -O2 -ffunction-sections -fdata-s=
ections -I$BLOCKSDS/libs/libnds/include" \
> BUILD_CC=3Dgcc \
> CC=3Darm-none-eabi-gcc \
> cf_cv_have_tcgetattr=3Dyes \
> ac_cv_func_gettimeofday=3Dyes \
> ac_cv_type_sigset_t=3Dno

The output from the configure script (config.log, config.status) would
tell us for example if it's using select or poll.

--=20
Thomas E. Dickey <[email protected]>
https://invisible-island.net

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