Make nsvg__parseColorRGB() independent of the current locale (memonon…

…en#139)

This commit fixes the locale dependency (re-)introduced by commit
c3ad36e by using sscanf() to parse
floating point values.

This modification uses nsvg__atof() which is independent of the
current locale.

src/nanosvg.h

@@ -1222,15 +1222,58 @@ static unsigned int nsvg__parseColorHex(const char* str)
 	return NSVG_RGB(128, 128, 128);
 }
 
+// Parse rgb color. The pointer 'str' must point at "rgb(" (4+ characters).
+// This function returns gray (rgb(128, 128, 128) == '#808080') on parse errors
+// for backwards compatibility. Note: other image viewers return black instead.
+
 static unsigned int nsvg__parseColorRGB(const char* str)
 {
-	unsigned int r=0, g=0, b=0;
-	float rf=0, gf=0, bf=0;
-	if (sscanf(str, "rgb(%u, %u, %u)", &r, &g, &b) == 3)		// decimal integers
-		return NSVG_RGB(r, g, b);
-	if (sscanf(str, "rgb(%f%%, %f%%, %f%%)", &rf, &gf, &bf) == 3)	// decimal integer percentage
-		return NSVG_RGB(roundf(rf*2.55f), roundf(gf*2.55f), roundf(bf*2.55f)); // (255 / 100.0f)
-	return NSVG_RGB(128, 128, 128);
+	int i;
+	unsigned int rgbi[3];
+	float rgbf[3];
+	// try decimal integers first
+	if (sscanf(str, "rgb(%u, %u, %u)", &rgbi[0], &rgbi[1], &rgbi[2]) != 3) {
+		// integers failed, try percent values (float, locale independent)
+		const char delimiter[3] = {',', ',', ')'};
+		str += 4; // skip "rgb("
+		for (i = 0; i < 3; i++) {
+			while (*str && (nsvg__isspace(*str))) str++; 	// skip leading spaces
+			if (*str == '+') str++;				// skip '+' (don't allow '-')
+			if (!*str) break;
+			rgbf[i] = nsvg__atof(str);
+
+			// Note 1: it would be great if nsvg__atof() returned how many
+			// bytes it consumed but it doesn't. We need to skip the number,
+			// the '%' character, spaces, and the delimiter ',' or ')'.
+
+			// Note 2: The following code does not allow values like "33.%",
+			// i.e. a decimal point w/o fractional part, but this is consistent
+			// with other image viewers, e.g. firefox, chrome, eog, gimp.
+
+			while (*str && nsvg__isdigit(*str)) str++;		// skip integer part
+			if (*str == '.') {
+				str++;
+				if (!nsvg__isdigit(*str)) break;		// error: no digit after '.'
+				while (*str && nsvg__isdigit(*str)) str++;	// skip fractional part
+			}
+			if (*str == '%') str++; else break;
+			while (nsvg__isspace(*str)) str++;
+			if (*str == delimiter[i]) str++;
+			else break;
+		}
+		if (i == 3) {
+			rgbi[0] = roundf(rgbf[0] * 2.55f);
+			rgbi[1] = roundf(rgbf[1] * 2.55f);
+			rgbi[2] = roundf(rgbf[2] * 2.55f);
+		} else {
+			rgbi[0] = rgbi[1] = rgbi[2] = 128;
+		}
+	}
+	// clip values as the CSS spec requires
+	for (i = 0; i < 3; i++) {
+		if (rgbi[i] > 255) rgbi[i] = 255;
+	}
+	return NSVG_RGB(rgbi[0], rgbi[1], rgbi[2]);
 }
 
 typedef struct NSVGNamedColor {