User:Furey/Box drawing problem - Revision history

Furey: more

2023-12-07T15:23:18Z

← Older revision		Revision as of 15:23, 7 December 2023
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	= Introduction =		= Introduction =

	When I watch other players on hardfought.org, and they are using curses, the boxes on screen are messed up. ~~Nethack~~ prints ~~a couple~~ of ~~chars of a~~ horizontal line segment ~~and~~ then ~~omits printing~~ the ~~rest~~ of the line segment.		When I watch other players on hardfought.org, and they are using curses, sometimes the boxes on screen are messed up. NetHack prints the top left corner, then one horizontal line segment character, then skips the rest of the horizontal line segment characters, then prints the upper right corner. Since most of the line segment chars are skipped, everything to the right is shifted and hard to read.

			(Tryna get a screenshot here, TBD).

	Other users have reported this problem with ttyrec readers.		Other users have reported this problem with ttyrec readers.
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	https://ecma-international.org/wp-content/uploads/ECMA-48_5th_edition_june_1991.pdf		https://ecma-international.org/wp-content/uploads/ECMA-48_5th_edition_june_1991.pdf

	This standard defines the relevant escape sequences.		8.3.103 REP - REPEAT

			This standard defines the relevant escape sequences. I think the problem happens when Player A has a terminfo entry that supports <code><i>char</i> ESC [ <i>digits</i> b</code>, and Player B has a terminal emulator that does not support REP.

	= Places where we could fix this =		= Places where we could fix this =
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	In the TNNT source (based on vanilla 3.6.7), the window subsystems are in win/. The file for the curses window system makes standard curses calls, particularly <code>initscr</code> to initialize the screen and <code>box</code> to draw boxes around the sub-windows.		In the TNNT source (based on vanilla 3.6.7), the window subsystems are in win/. The file for the curses window system makes standard curses calls, particularly <code>initscr</code> to initialize the screen and <code>box</code> to draw boxes around the sub-windows.

			We cannot fix this by changing the call to <code>box</code> to print individual line drawing chars. ncurses generates the REP sequence during normal curses optimization by noticing repeated chars, even if the application generated these chars one by one.

	NetHack hack 1: hack the code around the call to <code>initscr</code> to use a synthetic terminal type that has <code>rep@</code> cancelled out. This is difficult because <code>initscr</code> takes no parameters at all, so we have to manipulate the environment variables around it.		NetHack hack 1: hack the code around the call to <code>initscr</code> to use a synthetic terminal type that has <code>rep@</code> cancelled out. This is difficult because <code>initscr</code> takes no parameters at all, so we have to manipulate the environment variables around it.
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	Advantages: there is only one ncurses shared library per system.		Advantages: there is only one ncurses shared library per system.

	Disadvantages: rebuilding system library from source.		Disadvantages: rebuilding system library from source is difficult and may not replicate vendor build exactly, breaking unknown things.

	== terminfo source ==		== terminfo source ==

	Edit all the terminal descriptions to cancel the <code>rep</code> capability. Then rebuild the terminfo files.		Edit all the terminal descriptions to cancel the <code>rep</code> capability. Then rebuild the terminfo files. It's likely that most terminfo entries inherit <code>rep</code> from a small number of base entries, so the actual editing would be small.

	Advantages: easy to do.		Advantages: easy to do.
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	== dgl source ==		== dgl source ==

	~~I haven't looked at this one yet. However, if I understand correctly,~~ dgl is small, built from source (as opposed to coming as system software, which is harder to customize), and already ~~supports the 's' command for messing with~~ the data stream.		dgl is small, built from source (as opposed to coming as system software, which is harder to customize), and already modifies the data stream.

	We could filter the data stream for the ansi sequence <code><i>char</i> ESC [ <i>digits</i> b</code> and replace it with b+1 copies of <code><i>char</i></code>.		We could filter the data stream for the ansi sequence <code><i>char</i> ESC [ <i>digits</i> b</code> and replace it with b+1 copies of <code><i>char</i></code>. Just add another state machine to the existing code.

	Advantages: easy to do.		Advantages: easy to do.
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	Could do the hack described under dgl source.		Could do the hack described under dgl source.

	Advantages: would work instantly on historical ttyrecs.		Advantages: would work instantly on historical ttyrecs. is principled, because it makes the ttyrec player more compliant with ECMA-48.

	Disadvantages: I have no idea how many ttyrec players there are.		Disadvantages: I have no idea how many ttyrec players there are.
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	I looked at some hterm source. They have an "unimplemented, TBD" for <code><i>char</i> ESC [ <i>digits</i> b</code>. Problem might be that in the context where the function handler for <code>ESC [ <i>digits</i> b</code> gets called, the <i>digits</i> are available, but the previous <i>char</i> may not be. I would have to look harder at the hterm source.		I looked at some hterm source. They have an "unimplemented, TBD" for <code><i>char</i> ESC [ <i>digits</i> b</code>. Problem might be that in the context where the function handler for <code>ESC [ <i>digits</i> b</code> gets called, the <i>digits</i> are available, but the previous <i>char</i> may not be. I would have to look harder at the hterm source.

			Advantages: would fix the problem for everybody who uses hterm.

			Disadvantages: may require more state than a 1-line fix (to store the previous <i>char</i>). Requires maintaining a local patch until if and when upstream maintainers accept it.

Furey: /* hterm */ typo fix

2023-12-07T05:48:31Z

hterm: typo fix

← Older revision		Revision as of 05:48, 7 December 2023
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	Dunno how popular hterm is. Both NAO and hardfought offer it, though, and it's nice for playing nethack without installing any software.		Dunno how popular hterm is. Both NAO and hardfought offer it, though, and it's nice for playing nethack without installing any software.

	I looked at some hterm source. They have an "unimplemented, TBD" for <code><i>char</i> ESC [ <i>digits</i> b</code>. Problem might be that in the context where the function handler for <code>ESC [ <i>digits</i> b</code> gets called, the <i>digits></i> are available, but the previous <i>char</i> may not be. I would have to look harder at the hterm source.		I looked at some hterm source. They have an "unimplemented, TBD" for <code><i>char</i> ESC [ <i>digits</i> b</code>. Problem might be that in the context where the function handler for <code>ESC [ <i>digits</i> b</code> gets called, the <i>digits</i> are available, but the previous <i>char</i> may not be. I would have to look harder at the hterm source.

Furey: /* Introduction */ wording change

2023-12-07T05:46:19Z

Introduction: wording change

← Older revision		Revision as of 05:46, 7 December 2023
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	Other users have reported this problem with ttyrec readers.		Other users have reported this problem with ttyrec readers.

	The problem happens when Player A is playing a game, but Player B is watching it, either through dgl or a ttyrec player. Usually, Player A has a <code>TERM</code> environment variable that works fine for whatever terminal emulator Player A is using. However, the raw bytestream that looks fine for Player A does not look fine for Player B. It usually works, but we have run into this issue where Player A has a <code>TERM</code> that ~~supports~~ the ANSI repeat character ~~sequence~~, and Player B is using a slightly different terminal emulator that does not support this sequence.		The problem happens when Player A is playing a game, but Player B is watching it, either through dgl or a ttyrec player. Usually, Player A has a <code>TERM</code> environment variable that works fine for whatever terminal emulator Player A is using. However, the raw bytestream that looks fine for Player A does not look fine for Player B. It usually works, but we have run into this issue where Player A has a <code>TERM</code> that offers the ANSI repeat character capability, and Player B is using a slightly different terminal emulator that does not support this sequence.

	= ECMA-48 standard =		= ECMA-48 standard =

Furey: First round, brain dump.

2023-12-07T05:44:57Z

First round, brain dump.

New page

= Introduction =

When I watch other players on hardfought.org, and they are using curses, the boxes on screen are messed up. Nethack prints a couple of chars of a horizontal line segment and then omits printing the rest of the line segment.

Other users have reported this problem with ttyrec readers.

The problem happens when Player A is playing a game, but Player B is watching it, either through dgl or a ttyrec player. Usually, Player A has a <code>TERM</code> environment variable that works fine for whatever terminal emulator Player A is using. However, the raw bytestream that looks fine for Player A does not look fine for Player B. It usually works, but we have run into this issue where Player A has a <code>TERM</code> that supports the ANSI repeat character sequence, and Player B is using a slightly different terminal emulator that does not support this sequence.

= ECMA-48 standard =

https://ecma-international.org/wp-content/uploads/ECMA-48_5th_edition_june_1991.pdf

This standard defines the relevant escape sequences.

= Places where we could fix this =

== NetHack source ==

In the TNNT source (based on vanilla 3.6.7), the window subsystems are in win/. The file for the curses window system makes standard curses calls, particularly <code>initscr</code> to initialize the screen and <code>box</code> to draw boxes around the sub-windows.

NetHack hack 1: hack the code around the call to <code>initscr</code> to use a synthetic terminal type that has <code>rep@</code> cancelled out. This is difficult because <code>initscr</code> takes no parameters at all, so we have to manipulate the environment variables around it.

NetHack hack 2: after initscr(), add a line: <code>SP->_rep_cost = 999999;</code>. This would dissuade ncurses runtime from using the terminfo capability for repeating characters. Need to use gdb on nethack to find out the actual name of SP, and need to finagle the headers to get the right private header file for the internal SP struct.

Advantages: we build NetHack from source already.

Disadvantages: hardfought has 21 versions of NetHack (as of this writing).

== ncurses source ==

Internals of ncurses uses SP->_rep_cost to choose when to use repeated char capability. Just disable one block of code and rebuild ncurses from source.

Advantages: there is only one ncurses shared library per system.

Disadvantages: rebuilding system library from source.

== terminfo source ==

Edit all the terminal descriptions to cancel the <code>rep</code> capability. Then rebuild the terminfo files.

Advantages: easy to do.

Disadvantages: again, touching a system database.

== dgl source ==

I haven't looked at this one yet. However, if I understand correctly, dgl is small, built from source (as opposed to coming as system software, which is harder to customize), and already supports the 's' command for messing with the data stream.

We could filter the data stream for the ansi sequence <code>char ESC [ digits b</code> and replace it with b+1 copies of <code>char</code>.

Advantages: easy to do.

Disadvantages: works only for ansi based terminal types.

== ttyrec players ==

Could do the hack described under dgl source.

Advantages: would work instantly on historical ttyrecs.

Disadvantages: I have no idea how many ttyrec players there are.

== hterm ==

Dunno how popular hterm is. Both NAO and hardfought offer it, though, and it's nice for playing nethack without installing any software.

I looked at some hterm source. They have an "unimplemented, TBD" for <code>char ESC [ digits b</code>. Problem might be that in the context where the function handler for <code>ESC [ digits b</code> gets called, the digits> are available, but the previous char may not be. I would have to look harder at the hterm source.