43805: make nearcolor module use the default colour rather than black as a fallback

3 files changed, 10 insertions, 4 deletions

diff --git a/ChangeLog b/ChangeLog
index 636ea4dd7..41a2f7aa9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,8 @@
 2018-11-08  Oliver Kiddle  <okiddle@yahoo.co.uk>
 
+	* 43805: Src/Modules/nearcolor.c, Src/prompt.c: make nearcolor
+	module use the default colour rather than black as a fallback
+
 	* 43804: Src/prompt.c: also need to be able to turn colour
 	attributes back into hex triples for region_highlight variable
 
diff --git a/Src/Modules/nearcolor.c b/Src/Modules/nearcolor.c
index b51b4fd2c..0b9877bf4 100644
--- a/Src/Modules/nearcolor.c
+++ b/Src/Modules/nearcolor.c
@@ -146,13 +146,14 @@ 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);