Re: why terminal resize changes size of windows?

[Thomas Dickey]

On Fri, Feb 11, 2022 at 09:21:13AM +0100, Leon Winter wrote:
> Hi Pavel,
> 
> this is how I do it:
> 
> void ignore_handler (int)
> {
> }

well, you _can_ do that, but then (n)curses is of no use in optimizing the
screen after SIGWINCH.

In dialog, I re-layout the screen on reading KEY_RESIZE,
which works well enough.
 
> // somewhere else before initscr ()
> struct sigaction ignore;
> memset (&ignore, 0, sizeof ignore);
> ignore.sa_handler = ignore_handler;
> sigaction (SIGWINCH, &ignore, 0);
> 
> Regards,
> Leon
> 
> On Fri, Feb 11, 2022 at 03:55:04AM +0100, Pavel Stehule wrote:
> > pá 11. 2. 2022 v 3:34 odesílatel Pavel Stehule <pavel.stehule@gmail.com>
> > napsal:
> > 
> > >
> > >
> > > pá 11. 2. 2022 v 1:35 odesílatel Thomas Dickey <dickey@his.com> napsal:
> > >
> > >> On Thu, Feb 10, 2022 at 11:54:00AM +0100, Pavel Stehule wrote:
> > >> > Hi
> > >> >
> > >> > I found an interesting issue. When I resize the terminal, so some
> > >> windows
> > >> > are partially out of screen, the window size is reduced. From this
> > >> moment,
> > >> > the window lost original size, and the size of window is related to
> > >> size of
> > >> > screen.
> > >>
> > >> As I pointed out here:
> > >>
> > >> https://lists.gnu.org/archive/html/bug-ncurses/2020-08/msg00011.html
> > >>
> > >> windows don't extend outside the screen.
> > >>
> > >> When ncurses is handling SIGWINCH, it shrinks windows to fit in the
> > >> screen.
> > >>
> > >
> > >
> > Is it possible to disable this feature? Maybe in the future, by some
> > setting? I am author or pspg https://github.com/okbob/pspg
> > 
> > and this feature was probably the biggest issue when I worked on it. The
> > user of pspg can resize the terminal at any moment. And after resizing I
> > need to recheck all windows if they are the correct size. I understand, so
> > the signal handler can shrink some windows, but what is strange, it can
> > extend some windows too. Maybe the shrinking can be replaced by some flags
> > that can be detected from applications like fully visible, partially
> > visible, invisible. But the size of the window can be immutable.
> > 
> > Regards
> > 
> > Pavel
> > 
> > 
> > 
> > > ok
> > >
> > > Thank you for info
> > >
> > > Regards
> > >
> > > Pavel
> > >
> > >>
> > >> >
> > >> > It can be easy demonstrated by example:
> > >> >
> > >> > #include <ncurses.h>
> > >> >
> > >> > int
> > >> > main()
> > >> > {
> > >> >     int     c;
> > >> >     WINDOW *win;
> > >> >
> > >> >     initscr();
> > >> >
> > >> >     clear();
> > >> >     noecho();
> > >> >     cbreak();
> > >> >     curs_set(0);
> > >> >     keypad(stdscr, TRUE);
> > >> >
> > >> >     win = newwin(20, 40, 15,15);
> > >> >
> > >> >     timeout(250);
> > >> >
> > >> >     while (c != 'q')
> > >> >     {
> > >> >         int lines, cols;
> > >> >
> > >> >         clear();
> > >> >
> > >> >         /* termina size */
> > >> >         mvprintw(10, 10, "terminal: %d, %d", LINES, COLS);
> > >> >         clrtoeol();
> > >> >
> > >> >         /* stdscr size */
> > >> >         getmaxyx(stdscr, lines, cols);
> > >> >         mvprintw(11, 10, "stdscr: %d, %d", lines, cols);
> > >> >         clrtoeol();
> > >> >
> > >> >         /* win size */
> > >> >         getmaxyx(win, lines, cols);
> > >> >         mvprintw(12, 10, "win: %d, %d", lines, cols);
> > >> >         clrtoeol();
> > >> >
> > >> >         refresh();
> > >> >
> > >> >         wclear(win);
> > >> >         box(win, 0,0);
> > >> >         wrefresh(win);
> > >> >
> > >> >         c = getch();
> > >> >     }
> > >> >
> > >> >     endwin();
> > >> > }
> > >> >
> > >> > when running, try to reduce terminal size to 20 lines, 40 cols. After
> > >> > increasing terminal size, the size of window win is increased too.
> > >> >
> > >> > What is the reason for this behaviour?
> > >> >
> > >> > Regards
> > >> >
> > >> > Pavel Stehule
> > >>
> > >>
> > >>
> > >>
> > >>
> > >> --
> > >> Thomas E. Dickey <dickey@invisible-island.net>
> > >> https://invisible-island.net
> > >> ftp://ftp.invisible-island.net
> > >>
> > >
> 

-- 
Thomas E. Dickey <dickey@invisible-island.net>
https://invisible-island.net
ftp://ftp.invisible-island.net

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