degesch: enable bright backgrounds on 8-color terms

1 files changed, 23 insertions, 6 deletions

diff --git a/degesch.c b/degesch.c
index 35dcce0..4914bc4 100644
--- a/degesch.c
+++ b/degesch.c
@@ -2227,19 +2227,36 @@ attribute_printer_update (struct attribute_printer *self)
 	int bg = attribute_printer_decode_color
 		(self->want_background, &bg_is_bright);
 
-	// TODO: (INVERSE | BOLD) should be used for bright backgrounds
-	//   when possible, i.e. when the foreground shouldn't be bright as well
-	//   and when the BOLD attribute hasn't already been set
 	int attributes = self->want;
-	if (attributes & ATTRIBUTE_INVERSE)
+	bool have_inverse = !!(attributes & ATTRIBUTE_INVERSE);
+	if (have_inverse)
 	{
 		bool tmp = fg_is_bright;
 		fg_is_bright = bg_is_bright;
 		bg_is_bright = tmp;
 	}
 
-	if (fg_is_bright) attributes |= ATTRIBUTE_BOLD;
-	if (bg_is_bright) attributes |= ATTRIBUTE_BLINK;
+	// In 8 colour mode, some terminals don't support bright backgrounds.
+	// However, we can make use of the fact that the brightness change caused
+	// by the bold attribute is retained when inverting the colours.
+	// This has the downside of making the text bold when it's not supposed
+	// to be, and we still can't make both colours bright, so it's more of
+	// an interesting hack rather than anything else.
+	if (!fg_is_bright && bg_is_bright && have_inverse)
+		attributes |= ATTRIBUTE_BOLD;
+	else if (!fg_is_bright && bg_is_bright
+		&& !have_inverse && fg >= 0 && bg >= 0)
+	{
+		// As long as none of the colours is the default, we can swap them
+		int tmp = fg; fg = bg; bg = tmp;
+		attributes |= ATTRIBUTE_BOLD | ATTRIBUTE_INVERSE;
+	}
+	else
+	{
+		// This is what works on normal, decent terminals
+		if (fg_is_bright) attributes |= ATTRIBUTE_BOLD;
+		if (bg_is_bright) attributes |= ATTRIBUTE_BLINK;
+	}
 
 	attribute_printer_reset (self);