regression: resize/resizing window while command is executing is impartially felt by mc

[howaboutsynergy]

What steps will reproduce the problem?

1. start 'mc' within an xfce4-terminal window
2. run this command in 'mc':

read -rp "press enter after resizing xfce4-terminal window"

3. resize the window by making it larger in both X and Y directions
4. press Enter to the prompt in 2.
5. press Enter if prompted by 'mc' to "Press any key to continue..." to return to 'mc' panels

What is the expected output?

the panels are resized to the new window size

What do you see instead?

the panels are the same size as before the command in 2. got executed, but the lower bar (with the F1-F10 keys info) is resized correctly in the X direction.

(screenshots will be attached)

$ LC_MESSAGES=C mc -V
GNU Midnight Commander 4.8.23-75-g0ef1737aa
Built with GLib 2.62.0
Using the S-Lang library with terminfo database
With builtin Editor
With subshell support as default
With support for background operations
With mouse support on xterm
With internationalization support
With multiple codepages support
Virtual File Systems: cpiofs, tarfs, sfs, extfs, ftpfs, sftpfs, fish
Data types: char: 8; int: 32; long: 64; void *: 64; size_t: 64; off_t: 64;

$ LC_MESSAGES=C mc -F
Home directory: /home/user
Profile root directory: /home/user

[System data]
    Config directory: /etc/mc/
    Data directory:   /usr/share/mc/
    File extension handlers: /usr/lib/mc/ext.d/
    VFS plugins and scripts: /usr/lib/mc/
	extfs.d:        /usr/lib/mc/extfs.d/
	fish:           /usr/lib/mc/fish/

[User data]
    Config directory: /home/user/.config/mc/
    Data directory:   /home/user/.local/share/mc/
	skins:          /home/user/.local/share/mc/skins/
	extfs.d:        /home/user/.local/share/mc/extfs.d/
	fish:           /home/user/.local/share/mc/fish/
	mcedit macros:  /home/user/.local/share/mc/mc.macros
	mcedit external macros: /home/user/.local/share/mc/mcedit/macros.d/macro.*
    Cache directory:  /home/user/.cache/mc/

$ mc --configure-options
 '--prefix=/usr' '--sysconfdir=/etc' '--libexecdir=/usr/lib' '--enable-background' '--enable-network' '--enable-netcode' '--enable-charset' '--enable-nls' '--with-vfs' '--with-edit' '--with-screen=slang' '--without-x' '--without-samba' '--without-gpm-mouse' '--without-gnome' '--without-debug' '--without-included-gettext' '--disable-dependency-tracking' '--enable-tests'

[howaboutsynergy]

step1 aka before

[howaboutsynergy]

step 2&3 aka middle

[howaboutsynergy]

after step 5

[andrew_b]

The regression was introduced in [37ffc024225fd2ef1016babf3cbbeabce4a32899].

[andrew_b]

Before [37ffc024225fd2ef1016babf3cbbeabce4a32899] we had mc_global.tty.winch_flag that was set in sigwinch_handler(), than it checked some times (note: checked but no reset) and finally reset in dialog_change_screen_size().

Currently we have tty_got_winch() function that checks whether SIGWINCH was raised. But this function has side effect: the virtual SIGWINCH flag is reset after read. 'Virtual flag' means the non-emptiness of FIFO. If tty_got_winch() is sequentially called several times, only first call can return TRUE (FIFO was not empty at this moment), other calls return FALSE (read from an empty FIFO). Finally, dialog_change_screen_size() may not be called in dialog event loop in frontend_dlg_run(). Such case we have if SIGWINCH is raised while subshell is active.

I've tried fix that in

branch: 4019_resize_fix
changeset:4c36a5c8ea3386fbdf6b911986092fac11a0508a

But I'm afraid it is overcomplicated compared to using a simple variable before [37ffc024225fd2ef1016babf3cbbeabce4a32899].

[ossi]

can't resist placing a big fat "told you so" here. :P

did something go wrong while committing the fix? what i see on trac cannot possibly be complete (two one-liners in two files, and it doesn't match the commit message).

[andrew_b]

Replying to ossi:

did something go wrong while committing the fix?

Indeed. Sorry. Fixed.

[ossi]

ok, patch doesn't look bad (disclaimer: i did not examine the whole context the code lives in). some observations:

• typo in commit message: "check whether it [i]s empty"
• comment says "no timeout", but you actually mean "instant timeout" (or "don't block")
• the original code had a second flush around line 530 in execute.c. that whole hack *might* be obsolete now, but that needs investigation.

[andrew_b]

Replying to ossi:

• typo in commit message: "check whether it [i]s empty"

Commit message will be fixed before merge.

• comment says "no timeout", but you actually mean "instant timeout" (or "don't block")

Fixed

• the original code had a second flush around line 530 in execute.c. that whole hack *might* be obsolete now, but that needs investigation.

Restored.

[howaboutsynergy]

I tried this ​https://github.com/MidnightCommander/mc/compare/4019_resize_fix.patch on top of 4.8.23.82.gb633256c7-1 and it works! Thank you.

[andrew_b]

Merged to master: [2cf2a183ec24a2b6fc769a9abfefadfc2bdabf59].