Xterm.js: 'restore cursor' restoring position but not text attributes

[7PH]

I had some issues working with some VT100 escape sequences:

• save cursor (ESC 7) (DECSC)
• restore cursor (ESC 8) (DECRC)

Usually, a VT100 terminal should save the cursor position but also characters attributes when writing a save cursor escape sequence
The characters attributes should be restored when writing a restore cursor.

Currently, the position of the cursor is saved and restored but not the characters attributes.

I've tested the behavior of the save/restore escape sequences on other VT100 implementations to ensure they were handling it:

• gnome-terminal
• terminator
• hterm

I'll give some details below, and will start working on a solution since I need it for myself.
Keep up the great work!

Details

• Browser and browser version: Chromium: Version 62.0.3202.89 (Developer Build) built on Debian buster/sid, running on Debian buster/sid (64-bit)
• OS version: debian buster/sid
• xterm.js version: 3.4.1

Steps to reproduce

Here's the VT100 escape sequences used for testing:

\x1b[0m (attributes off)
\x1b[1;1f (reset origin)
\x1b[2J (clear)
\x1b7 (save cursor state)
\x1b[7m (set negative color)
                        <colored> (just some output)
\x1b8 (restore cursor state)
<should not be colored>\n\r (another output - will be printed in negative color in xtermjs)

With xtermjs, "should not be colored" is colored

xterm.write('\x1b[0m\x1b[1;1f\x1b[2J\x1b7\x1b[7m                        <colored>\x1b8<should not be colored>\n\r');
// will print:
// "<should not be colored> <colored>"

In a bash, "should not be colored" won't be colored

printf '\x1b[0m\x1b[1;1f\x1b[2J\x1b7\x1b[7m                        <colored>\x1b8<should not be colored>\n\r'
# will print
# "<should not be colored> <colored>"

How to fix

Seems to me that text attributes should be saved and restored along with the position, here.
Here is how hterm is handling the save/restore cursor

edit:
All the characters attributes (fg color, bg color, and the special flag modes: bold, italic, negative, ..) are stored in the 'curAttr' attribute of the 'Terminal' class. Saving a copy of this attribute should be enough to restore all the characters attributes at once.

[egmontkob]

VTE used to be buggy too; perhaps you can find a few interesting bits in VTE 731205.

[jerch]

@7PH Since you are modifying DECSC anyways maybe you can have a look at https://vt100.net/docs/vt510-rm/DECSC.html, there are some more terminal attributes still missing, that should be handled as well.

[Tyriar]

If not we should create a separate issue for it. Capturing all these should probably be done in something like an ICursorState state object to keep things organized.

[Tyriar]

Merged in the PR and forked off the rest of the properties to https://github.com/xtermjs/xterm.js/issues/1526