Re: [BUG?] If true-color is used, overlapping colors do not work

[Oliver Kiddle <okiddle@xxxxxxxxxxx>]

Sebastian Gniazdowski wrote:
> I was testing on Linux, via docker. $termcap[Co] shows 8, the same
> $terminfo[colors]. The zsh/nearcolor fails and maybe it could fail a
> little better?

I admit that black, as opposed to the default colour isn't clever. The
patch changes this.

> Color 30 is apparently black. Maybe zsh/nearcolor could use (compare
> against) first 8 or 16 colors when $termcap[Co] <= 8?

The first 16 colours vary between terminals and are also commonly
configurable so nearcolor never compares against them. 

There is an escape sequence for getting colour definitions but I don't
think trying to use it gains us much.

Oliver


diff --git a/Src/Modules/nearcolor.c b/Src/Modules/nearcolor.c
index 128658e20..7ebc75365 100644
--- a/Src/Modules/nearcolor.c
+++ b/Src/Modules/nearcolor.c
@@ -117,13 +117,14 @@ mapRGBto256(int red, int green, int blue)
 static int
 getnearestcolor(UNUSED(Hookdef dummy), Color_rgb col)
 {
+    /* we add 1 to the colours so that colour 0 (black) is
+     * distinguished from runhookdef() indicating that no
+     * hook function is registered */
     if (tccolours == 256)
 	return mapRGBto256(col->red, col->green, col->blue) + 1;
     if (tccolours == 88)
 	return mapRGBto88(col->red, col->green, col->blue) + 1;
-    /* returning 1 indicates black rather than failure (0) so this
-     * module still serves to prevent fallback on true color */
-    return 1;
+    return -1;
 }
 
 static struct features module_features = {
diff --git a/Src/prompt.c b/Src/prompt.c
index 377015ad8..568bfc2a9 100644
--- a/Src/prompt.c
+++ b/Src/prompt.c
@@ -1650,10 +1650,12 @@ match_colour(const char **teststrp, int is_fg, int colour)
 		return TXT_ERROR;
 	    *teststrp = end;
 	    colour = runhookdef(GETCOLORATTR, &color) - 1;
-	    if (colour < 0) { /* no hook function added, try true color (24-bit) */
+	    if (colour == -1) { /* no hook function added, try true color (24-bit) */
 		colour = (((color.red << 8) + color.green) << 8) + color.blue;
 		return on | (is_fg ? TXT_ATTR_FG_24BIT : TXT_ATTR_BG_24BIT) |
 			(zattr)colour << shft;
+	    } else if (colour <= -2) {
+		return TXT_ERROR;
 	    }
 	} else if ((named = ialpha(**teststrp))) {
 	    colour = match_named_colour(teststrp);