Inconsistent console display background on black-on-white terminal emulators

[PoC-dev]

This issue pertains to at least all SDL-Hercules 4 releases. Only today, I'm taking my time to report it. I admit, it's a low priority, largely cosmetic thing.

If one uses a terminal emulator with black characters on a white background — default setting for the macOS terminal ever since, and consistent with earlier applications such as NCSA telnet in the 1990's — only parts of the screen with actual output are erased and initialized to feature black background:

Note that the color setting on the Mac is not simply "white on black terminal set to reverse video", but the background color is indeed white. I guess that's important to know for duplicating the issue. Also, this happens only when Hercules runs within a screen-session! A combination of screen (4.09.00 (GNU) 30-Jan-22), and Hercules!

I have written an (unrelated) application that uses ncurses to output a full-screen display with black background and initially faced the same issue. Until I found, that the background needs to be set explicitly:

init_pair(CP_GREEN, COLOR_GREEN, COLOR_BLACK);
bkgd(COLOR_PAIR(CP_GREEN));

This application does not show the documented behavior, even within screen.

Note: Ncurses uses predefined color pairs as attributes, which can be switched on and off during program execution.

I have not found any curses initialization routines in the Hercules routines, but termios.h is included. So POSIX terminal interface routines are used.

After some grepping and looking at files, I'm lost. I see panel.c has a function set_panel_colors() and a variable sysblk.pan_colors, but after assembling the puzzle pieces, this seems to be related to this text in the documentation:

MSGCOLOR=DARK displays colorized panel messages meant for 'dark' panels (such as white text on black background) whereas MSGCOLOR=LIGHT is obviously meant for panels using dark text on light backgrounds. Only 'E' (error), 'W' (warning), 'D' (debug) and 'I' (informational) messages are colorized. Any message not detected as a Hercules "HHCnnnnnX" format message are not colorized.

So this is not for the view shown in my screen shot, but for the command entry panel. This strongly hints towards the described screen output is not the result of a configuration issue. 😊

I don't understand how Termios works, so I'm unable to provide a proper patch to set the background color as described above.

[PoC-dev]

Interestingly, the described error does not happen with an empty hercules.cnf. My suspicion that it might be related to PANOPT was wrong, tested this as the only parameter.

For completeness, here's a configuration which shows the issue.

[Fish-Git]

I'm confused.

It appears you are claiming that when PANOPT is set incorrectly (i.e. fails to match your terminal's actual settings), Hercules's extended panel screen does not paint correctly. Yes? Is that what you are claiming?

Does it paint correctly when your PANOPT setting does correctly match your terminal settings?

Also, does the default HMC panel (that displays the Hercules messages) also paint incorrectly when PANOPT is incorrectly set?

[PoC-dev]

I'm confused.

I'm a little, too.

It appears you are claiming that when PANOPT is set incorrectly (i.e. fails to match your terminal's actual settings), Hercules's extended panel screen does not paint correctly. Yes? Is that what you are claiming?

No. I say that my version of a configuration does show the issue, while an empty configuration file does not.

The closest match to "that could be the culprit" I could find was PANOPT, but setting this in my testing config file to the same settings I use with a running instance, does not show the painting issue.

Does it paint correctly when your PANOPT setting does correctly match your terminal settings?

Please elaborate upon "correctly". As far as I've understood in the source, the color settings to be chosen are for the log/command panel, not for the overview panel, and default is no color. So I've never touched these. Please correct me if I'm wrong.

Also, does the default HMC panel (that displays the Hercules messages) also paint incorrectly when PANOPT is incorrectly set?

Nope, that's fine (white BG, black text, red status line) in both testing cases:

• empty config file
• configuration as attached to this issue.

[Fish-Git]

Please elaborate upon "correctly". As far as I've understood in the source, the color settings to be chosen are for the log/command panel, not for the overview panel,

Well, yes, BUT... AFAIK a system's black on white or white on black terminal setting affects (or should affect, yes?) BOTH screens, yes? So if your system's default/current terminal setting is black text on a white background , then the Hercules "extended" (overview) panel should also be black text on a white background too (yes?), and your documented problem should not be occuring! (Yes?)

I mean, haven't checked, but AFAIK, both panels are painted identically as far as their text on backgound color is concerned, yes? That is to say, the only thing that MSGCOLOR= should affect are the error, warning, debug and informational messages on the messages panel. The chosen setting should not be impacting the "overview" (extended) panel display AT ALL. Yes? It should continue to be painted as normal (or at least NOT the way yours is being painted!)

I know nothing about Ncurses OR Termios. That's a Linux thing. But providing a consistent standard(?) terminal I/O interface for the Hercules panels (which includes the "extended" panel that is displayed when the 'Esc' key is pressed too) is something that has LONG been left unaddressed in Hercules, In fact, that is one of the parts (pieces) of Hercules that I intended to eventually move to an External Package.

Someone (NOT ME!) really needs to fix this part of Hercules once and for all. Until such is eventually done, I fear problems such as the one you describe in this issue are going to continue to occur!   :(

BOTTOM LINE: I don't know what's going on or what's causing it, but whatever it is is beyond my abilities to correct it. I don't know enough about Linux. Someone else more skilled at Linux is going to have to take this on.

[PoC-dev]

Well, yes, BUT... AFAIK a system's black on white or white on black terminal setting affects (or should affect, yes?) BOTH screens, yes?

Ah. Yes, it maybe should. But it doesn't, in this case.

Note: Terminal Setting is the setting of the emulator, not Hercules. I've always left the Hercules setting at default = no color.

So if your system's default/current terminal setting is black text on a white background , then the Hercules "extended" (overview) panel should also be black text on a white background too (yes?), and your documented problem should not be occuring! (Yes?)

I agree. Either that, or I'd expect the background to be set to black properly, by the application.

I mean, haven't checked, but AFAIK, both panels are painted identically as far as their text on backgound color is concerned, yes?

I don't know for sure. But they certainly aren't, as I've observed.

That is to say, the only thing that MSGCOLOR= should affect are the error, warning, debug and informational messages on the messages panel. The chosen setting should not be impacting the "overview" (extended) panel display AT ALL. Yes? It should continue to be painted as normal (or at least NOT the way yours is being painted!)

That matches my understanding from the source, and documentation.

I know nothing about Ncurses OR Termios. That's a Linux thing. But providing a consistent standard(?) terminal I/O interface for the Hercules panels (which includes the "extended" panel that is displayed when the 'Esc' key is pressed too) is something that has LONG been left unaddressed in Hercules, In fact, that is one of the parts (pieces) of Hercules that I intended to eventually move to an External Package.

I remember a discussion in the related group, yes.

Someone (NOT ME!) really needs to fix this part of Hercules once and for all. Until such is eventually done, I fear problems such as the one you describe in this issue are going to continue to occur!   :(

I think so, too.

BOTTOM LINE: I don't know what's going on or what's causing it, but whatever it is is beyond my abilities to correct it. I don't know enough about Linux. Someone else more skilled at Linux is going to have to take this on.

To make it easier, I've tried to find out what exactly causes the wrong background paint color. Very nasty. It's a combination of screen (4.09.00 (GNU) 30-Jan-22) and Hercules! So, it can be an issue of screen, or Hercules. 🙈

My ncurses based application (see above) does not show the issue described.

I honestly don't have the mental energy to dissect this issue in detail. IDK what to do.

[PoC-dev]

I have edited my initial bug report to reflect this latest finding about screen playing a role.

[gottfriedleibniz]

I have edited my initial bug report to reflect this latest finding about screen playing a role.

Based on the image, I suspect that background-color-erase (BCE) is disabled (or not supported). One remedy is to add defbce on to your .screenrc.

On your system, have you encountered similar issues with Vim and the terminal background colour bleeding into it while using screen? Or, assuming you use Vim, does your .vimrc set TERM=screen-256color or something similar?

[PoC-dev]

Based on the image, I suspect that background-color-erase (BCE) is disabled (or not supported). One remedy is to add defbce on to your .screenrc.

Yap, that helps greatly! I suggest to add this at an appropriate place in the documentation, since I have learned from list member postings, that on Linux, running Hercules in screen is quite often done. I suggest two spots:

• https://sdl-hercules-390.github.io/html/hercconf.html#PANOPT
• https://sdl-hercules-390.github.io/html/hercinst.html#operating – just below the second screenshot "hercules.exe managed semi-graphical panel"

On your system, have you encountered similar issues with Vim and the terminal background colour bleeding into it while using screen?

Nope.

Or, assuming you use Vim, does your .vimrc set TERM=screen-256color or something similar?

You assume correctly. 😊

No, I don't hard code terminal types in my ~/.vimrc. Those are supposed to be in an (correctly set) envvar and all applications are supposed to use this to get the terminal sequences right.

The built-terminal emulator of my Mac indeed sets TERM=screen-256color, which is inherited over ssh by the Linux-Server I run Hercules on.

[gottfriedleibniz]

AFAIK, Vim queries termcap/terminfo for flags such as background-color-erase and configures its internal variables accordingly. For Hercules, that seems a bit excessive.

Another solution could be to provide an additional PANOPT argument that allows the user to override how background colouring is handled. I whipped up a quick proof-of-concept for doing so.

An executive decision(TM) would be needed to determine which approach to take.

[Peter-J-Jansen]

Hi Patrik,

I'm not sure I can be of any help here, but as you mentioned macOS, under macOS I start hercules from a shell script in another shell script in an xterm session like this :

xterm -geometry 110x73+0+30 -fa 'Liberation Mono' -fs 11 -e "CONF/hercules $*" &

And if I do that without the 'fix' that follows, the hercules console background in the xterm would also be an annoying white. My 'fix' for that is creating an .Xdefaults file with the following content :

peter@pjm4:~$ cat .XDefaults
XTerm*Background: black
XTerm*Foreground: white
peter@pjm4:~$ 

I'm not sure if this would help you, I'd be interested to know.

Cheers,

Peter