[jed-users] Return not static string from C + 256+ colors terminal

[Nicholas Christopoulos <nereus@xxxxxxxxxxx>]

Greetings JED users.

Two questions

1. This is the code in C that used inside my patched version of Jed.
I didn't find in documentation how to return a string (except if it is
static string). So, I tried this solution that should work in theory
(and in assembly based on regular languages).

It is worked and seems correct, but there are no manual nor I found
something similar in JED's code.

I would like a confirmation that it is a correct solution.

```C
void cbm_popup_files_sl() {
	char	retf[PATH_MAX];
...
	// push copy of the string in
	// interpreters stack.
	// this is the returned string
	SLang_push_string(retf);
}

/* setup S-Lang interface */
static SLang_Intrin_Fun_Type CBRIEF_Intrinsics [] = {
...
MAKE_INTRINSIC("popup_files", cbm_popup_files_sl, STRING_TYPE, 0),
...
};
```

```S-Lang
...
selected_file = popup_files();
...
```

2. My second question, it is mostly a request.
It is easy to support the 256+ colors in linux / X11 terminals, but
inside from JED you cannot. Colors always ends-up to
tt_set_color(obj, fg, bg) where FG and BG are strings of the names of 16
VGA colors; anything else does not recognized. The set_color_esc() its
not documented and I don't know how to use it.

FYI:

If the terminfo reports 256 colors, then you can use 256 or more colors.
If the COLORTERM environment variable is set, then you can use 24bit
colors. Check both is safer.

```
> tput colors
256
```

There are at least three ways to use more colors in linux/X11 terminals

a) standard CSI

\e[38;2;r;g;bm Foreground RGB color
\e[48;2;r;g;bm Background RGB color

man -s 4 console_codes

```
Commands 38 and 48 require further arguments:

;5;x       256 color: values 0..15 are IBGR (black, red, green, ...
white), 16..231 a 6x6x6 color cube, 232..255 a grayscale ramp

;2;r;g;b   24-bit color, r/g/b components are in the range 0..255
```

This method is used often.

b) OSC

man -s 4 console_codes

```
ESC ] 4 ; num; txt ST   Set ANSI color num to txt.
ESC ] 10 ; txt ST       Set dynamic text color to txt.
```
The 'ST' (string termination) symbolizes the \033\\ or \007
In both cases the txt is a RGB number. It is not well documented.

examples:
/bin/echo -e "\033]4;7;rgb:ff/00/00\007 \033[37mHello - function 4"
/bin/echo -e "\033]10;rgb:ff/ff/00\033\\ Hello - function 10"

c) OSC second method

man -s 4 console_codes

```
ESC ]     OSC      (Should be: Operating system command) ESC ] P
nrrggbb: set palette, with parameter given in 7 hexadecimal digits
after the final P :-(. Here n is the color (0–15), and rrggbb indicates
the red/green/blue values (0–255). ESC ] R: reset palette
```

...

A script for testing (CSI method):

```print_console_colors.sh:
#!/bin/sh
awk 'BEGIN{\
    s="/\\/\\/\\/\\/\\"; s=s s s s s s s s;\
    for (colnum = 0; colnum<77; colnum++) {\
        r = 255-(colnum*255/76);\
        g = (colnum*510/76);\
        b = (colnum*255/76);\
        if (g>255) g = 510-g;\
        printf "\033[48;2;%d;%d;%dm", r,g,b;\
        printf "\033[38;2;%d;%d;%dm", 255-r,255-g,255-b;\
        printf "%s\033[0m", substr(s,colnum+1,1);\
    }\
    printf "\n";\
}'
```

Best regards

-- 
Nicholas Christopoulos <mailto:nereus@xxxxxxxxxxx>
Personal Pages: <https://nicholas-christopoulos.dev>
Github repositories: <https://github.com/nereusx>
_______________________________________________
For list information, visit <http://jedsoft.org/jed/mailinglists.html>.